4:38 Hi, I’m a naval architect! “Strength-to-buoyancy ratio” is complete and utter nonsense. The buoyant force is only a function of the volume of displacement of the hull (provided that the hull isn’t flooded). A fully-immersed cylinder with a 2m outer diameter will have exactly the same buoyant whether it is made of carbon fiber or steel or titanium. If your requirement is a certain inner diameter, the extra thickness will get you some more buoyant force, but you could get the same extra buoyant force by simply making the metal hull larger to achieve the same outer diameter, with the added benefit of slightly more available volume inside the submersible. TLDR: Archimedes is right and Stockton Rush is wrong.
@@JamieKunkaGlad to help! It’s relatively rare that my expertise is relative to something in the news, but when it is, I’m more than happy to help elevate the public discourse.
@@michaelimbesi2314 that is true , the buoyancy is proportional to the volume regardless of what materials the hull is made of. but i think what rush was referring to is that he wanted to achieve a certain buoyancy with the lightest materials possible to reduce the weight of the sub.
He was obviously referring to how using a lightweight material like carbon fiber reduces the overall weight of the sub vs using titanium. It shouldn't be so hard to read between the lines. You're just twisting his words to make them sound as bad as possible really.
I have been an aviation maintenance technician for 32 years, specializing in aircraft structural repair. I spent 10 years in The Air Force, 5 working on the B-2 Bomber and had a lot of composite repair training. I am not an engineer, just a repair technician. Watching the video of the Titan’s construction made me cringe. To me, they did nothing right and everything wrong. Watching them “clean” the Ti ring and bond it to the carbon made me gasp out loud. We had a saying, “Cleanliness is next to bondliness”.
Since you’re here: So does anything about the Titan’s construction make sense for the aerospace industry? Because I’ve wondered if Stockton was taking what he apparently knew as an aerospace engineer and just assumed that a vehicle for underwater works the same way as planes.
I too was appalled at whàt I saw of the layup! I've worked on aircraft,, boats, roçkets, atomic submarines since 1957! Worked with autoclaves And HYDROCLAVES. Also oñ filement winding machines. Yes, they were very naive iñ every respect, from the mixing of the àdesive to handling of materials! Did they use a vacuum chamber to remove the air from the adhesive? What was used to thicken the resin? Many questions!
Hi Chris, Retired USAF AFRL/ACO 2016 here. As a SME I applaud you for composite repair skills. I started the Mobile Training Team at the request of HI. In 2008 and personally trained over a hundred airmen in the field. In my opinion there were both design flaws and grossly inadequate manufacturing processes. This puts an unneeded smear on composite structures. The joint was the problem! Adhesives are great in shear not so good in tension terrible in peel strength. Some of the factors stressing the joint: dissimilar material stiffness, dissimilar material expansion due to temperature changes, hemispheres flatten out under pressure causing the bonding surface to dish out and put the joint in tension on the outer circumference. I was the principle manufacturing engineer on filament wound cases for the space shuttle boosters Air Force program to do a polar orbit. Canceled because of the Challenger disaster. In testing using water pressure the reverse loading condition of the submersible the joint was a big hurdle. At near 1000 psi the half dome hemisphere inflated like a balloon and the composite tube barely moved radially. This caused the Clevis joint on the dome to open up and expose the interior end of the pin to the pressure. The 2000 pounds of force on the end of the pin was like pulling the trigger on a gun. Pins were spit out like a machine gun as the joint failed in microseconds. The AFT joint failed 6000 psi water pressure intruded compressing the air to less than a golf ball size and blowing out the forward porthole and the after shockwave blew the composite tube apart. Only epoxy in that direction no fibers along the axis.
@@oneskydog6768 I too am curious about the bond and see it as a definite contender for the leading cause of failure. In addition to the points you've made, I'd like to add a few thoughts of my own. Having been in the composites industry for about 30 years, I have some experience with the processes and materials, although admittedly little with carbon fiber and zero with submersibles. I have been involved in design and manufacture of marine, wind blade, and infrastructure products. Much of my time was spent testing products, often to failure. I can see multiple possible paths to failure in this vessel. It could be due to engineering decisions, manufacturing processes, material choices, quality control issues, etc. It could be a combination of two or more bad decisions. As an example of just one line of questioning, the carbon fiber hull was bonded to a titanium ring. Was the ring adequately designed for the bond? Was the bond compromised by flexing of the carbon hull? Inward flexing of the hull could act as a lever on the bond line. Bonding dissimilar materials can be difficult to accomplish. If the hull was stiff enough to withstand pressure and not flex, it wouldn't act as a lever causing a failure of the bond. If the ring was designed differently, could it have helped support the hull and thus, the bond of the hull and ring? We could surely come up with similar questions for each of the components of this vessel. Most commentary on this tragedy leans towards speculation as fact. Watching a couple of videos where they show elements of the construction process doesn't turn us into experts on the structure and certainly doesn't make us qualified as failure analysis experts. I've commented on several videos where the overwhelming commentary is that the carbon hull failed, stated as fact. It's all speculation as nobody knows what actually failed. It could have been the carbon fiber, it could have been the bond interface between the carbon and the titanium rings. It could have been the viewport. It could have been something else. At this stage of the game, there is no one that "knows" what happened with any degree of certainty.
This is by far the best video I've seen on the topic. All of the points you make are right on, and there are a couple you didn't mention. I've 10 years experience related to the construction, testing and deployment of aluminum cylindrical pressure vessels rated for full ocean depth, and 6+ years winding thick carbon fiber cylinders. Regarding implosion testing, the weakest side of the aluminum cylinder begins to buckle, putting the interior surface of the aluminum under tension, and any resulting fracture begins there. Carbon fiber cylinders are strong under tension, that is, high pressure from the inside surface, but there is no lengthwise compression strength with carbon fiber. More to the point, when under extreme internal pressure, the carbon fiber cylinder actually grows physically in the radial direction. If under external pressure as with the Titan, the strength in the radial direction is unknown to me, but if the composite is pressed inward by the uniformly-exerted pressure, it is likely to shrink slightly. If this rate of dimensional change is even slightly different than the titanium end rings, this would produce shear forces at the glue joint during a dive. Each dive could stress and weaken the glue joint more and more. The only way I know to effectively bond titanium to carbon fiber is by a difficult process that involves more than just glue, and was not mentioned. Lastly, for carbon fiber with a high number of layers, as shown, many things, especially the fact that the epoxy shrinks while curing, often results in voids and tangential cracks internal to the cylinder which cannot be seen, but are revealed when a test section is cut from the cylinder and inspected. My supervisor has told me that metals expand with temperature, while carbon fiber shrinks with temperature. I don't know if that's true, but if it is, it would also be a problem. Thank you for your excellent video.
With all the new data coming out, your comment seems to have the most insight. Though from what i can understand the data points to delamination of the carbon fiber layers putting excessive force on the titanium end rings, specifically the inside wall of the Ti-CF overlap, causing them to shear off.
He approached other companies to build it but they turned him down (because they knew it was a terrible concept) so he got a bunch of plumbers to make a glorified PVC pipe... money doesn't buy intelligence.
One positive from this incident is the case study it gives to all future engineering students. Universities should come up with courses covering all the engineering concepts behind this failure.
The engineer behind the Hyatt Regency Walkway collapse in KC spent the rest of his life lecturing on the mistakes he made that lead up to the disaster.
Even myself, a layperson with 0 years working with composite fibres and 2-part epoxy-style adhesives, was staring with disbelief as they slid the two pieces together, by hand, IN AN OPEN WAREHOUSE AND IN STREET CLOTHES. *I've seen woodworkers do more prep work before applying layers of topcoat to a piece of furniture* - wearing full-body suits in a sealed environment, and so on. And no one's life is on the line if the finish being applied to the furniture you're working on has a bad spot or three. A bad spot or three on a deep-sea submersible, on the other hand, means instant death. Quite literally. Just unbelievable. You can't pretend you know what you're doing when building something like this. LIVES ARE ON THE LINE, YOU DAMN WELL BETTER BE SEXTUPLE-CHECKING EVERY TINY DETAIL AND ASKING EVERY EXPERT YOU CAN GET YOUR HANDS ON TO OFFER THEIR BEST TIPS. Firing everyone who told him "no" and hiring nothing but kids fresh out of college (who could be browbeaten or intimidated into never telling him "no") probably didn't help much, either. Why hire industry experts? Those guys are *EXPENSIVE* and will tell you "no" to your face. College grads, on the other hand, tend to work for a fraction of the salary and tell you what you want to hear, 'cause you're the CEO! The hubris on display throughout this whole sad saga borders on insanity, like Stockton truly believed that the Universe would bend to his whims, that all his "innovative engineering" was infallible, and that he could defy the laws of physics through sheer grit and determination (while saving a bunch of money in the process).
@@JamieKunka I am also a layperson but with an extensive background in a range of technical disciplines . GLUES RESINS AND EPOXIES HAVE CAUSED MANY DEATHS if not mixed properly ...BOSTON MA .. BIG DITCH TUNNEL PANEL DROP is a typical example ..it killed the occupants of a minivan when it dropped because the EPOXY used to anchor the suspension bolts ran like molasses in JULY. Besides the obvious being addressed by the expert analyst ...RUSH was too full of own self generating BS , he believed in his own BS as most legends of one`s own mind do enough so as not to listen to anyone, but his own misguided mind.
The engineer and those workers have blood on their hands now. Did any of them ride down in the Titan death trap at anytime I wonder? Who was the inspector working on this submersible, he or they too have blood on their hands. So did SR but he died in the implosion but I'm not sad that he went down with his flimsy submersible. PH should have known better and sounded the alarm, but would SR have listened to him?
What's even worse is the shop that made this "vessel" and glued it the way they did. Granted they probably did it based on the spec provided but I work in that industry and when we see shit that is an obvious no no we say something. The shop that made the shit is liable in a way as much as ocean gate in this instance. But that's my opinion
Rush's workshop is little better than mine (I am a musical instrument maker working at home). I take greater care in gluing and bonding than these guys do. Amazing. I will give him some credit: he went down with the ship.
Rush may not even deserve much credit for "going down with...". OceanGate's former finance director said that Stockton Rush asked her to be the head pilot for the Titan after the former pilot, David Lochridge, previously said he was fired for noting concerns about the sub's safety. She quit because of that.... or maybe she had limited experience with Game Controllers? Rush seemed eager to keep the money coming in and appearances up. Would it be too much to speculate if the finance director knew other valuable information that was best left buried at the bottom of an Ocean?
It should have been double prooffed. Meaning that if they were going to be operating at 6,000 feet, it should have been built for and tested at 12,000 ft.
correct it should’ve been common sense to have a Margin ,, if you’re towing a 7000 pound trailer, get a truck with a 9000 pound towing capacity, not a 7000 pound towing capacity.. I mean, this is nearly common sense in the engineering world, it’s astonishing. He was pushing it at the limit.
You're soo off I'm guessing your completely uneducated in the topic and just throwing numbers out that sound good. Most submersibles do 120% their operating depth, your talking about 200%. Titan didn't even have the extra 20% either, and since the carbon fiber tore on the very first dive it definitely wasn't even rated for Titanic's depths let alone had a safety margin.
@@sertank735 that's what an uneducated person would say, since industry standards are 120% and there's never been a problem till now. Titan didn't have that safety margin, it wasn't built right to handle the depths it was going to, the carbon fiber tore on the first dive, and yet you think its gonna somehow do double its operating depth? Geez, your so ignorant about submersibles idk why your even acting like you know what should be done and what is a good level of safety. 120% is actually more than enough, but your sub has to not only be built right but be able to handle 100% of it's operating depth without it falling apart every dive. Carbon fiber isn't a good submersible material period, nor should we take this accident and try to change industry standards when this sub had nothing to do with industry standards, and actually went so far off industry standards it imploded. The problem started at the design phase not at depth, the sub was just so bad it couldn't even operate 20-40% it's operating depth without the carbon fibers tearing. Every other submersible does 120% and has never had a single problem operating at 100%, because they didn't use carbon fiber and their design was actually good and safe. Just get educated if you wanna act like you know what your talking about, because clearly you don't.
Doomed from the get go ... no Clean Room, no Auto-Clave and no AS9102 certification to keep it all on the straight and narrow. But hey, that's just what my 40 years in Aerospace Composite Engineering tells me. Just imagine if Rush had invested in a "Thread laying machine" (TOWS) like we use on our F-35 Program ... much stronger ... and Rush wouldn't have been able to buy that expired (and obviously "re-tested" once) CF Tape from Boeing ! And THAT folks is why we call it "HALT" ... highly accelerated lifetime testing ... "bend it until it breaks" so you have a baseline. IMHO, the Hull imploded and had NOTHING to do with the Titanium flanges/dome; the acrylic view port and domes blew off like Champagne corks (Water cannot be compressed and it had to go somewhere) ... studs smooth as a shiny new whistle ~ zero threads left nor CF tear away on the mounting flanges (there are ZERO “Adhesives” on the professional/FMS market that don’t call for application of a “Primer” prior to the actual Adhesive). His "Design Engineers" sucked ... the hull was in "hoop" yet zero internal stringer supports nor sleeve to help keep it equalized; hull thickness would have needed to be approximately 17.6 inches thick without said support structure. All the "popping noise" on previous dives was the CF delaminating, transitioning from "Elastic" to "Plastic" state ... the fibers ripped out of the resin matrix bed and never able to re-seat; Rush would have known this had he bothered to perform NDI (ultrasonic or X-Ray) after each dive. Pity his hubris got in the way. Good presentation Jamie.
Yes, you’d think ultrasonic testing would have revealed the defects before the vessel was submerged. And also the ruptures that developed under pressure.
@@maxenielsen yes, it would have identified the delamination areas ... "X-Ray" for more accurate locations ... but he was such a cheapskate he skipped it.
I've worked as a NDT-technician in the windturbine business, and i'm apalled that the CF hull never went through any testings for airvoids or delaminations. A suicide waiting to happen, but there was no need to bring more.
BSME here. Carbon fiber has incredible strength in tension, not compression. In compression the strength is almost entirely that of the adhesive, not of the carbon. Foolish design, foolish testing methods, foolish egos.
I've been wondering about the titanium/carbon fibre interface as well. The bonding procedure taking place in an open industrial workshop and not in a cleanroom. The lack of proper safety equipment; scaffolds etc. No one suited up for clean operations, no vacuum chamber to pull air from the glue joint. The mixing of the glue in an open environment. It all seems quite amateur and hasty.
When I saw the clips of the assembly, I was thinking "Surely they had a vacuum chamber somewhere. Why didn't they mention it?". I don't know that much about epoxy, but I know that anyone doing serious work with it has to find a way to get rid of the inevitable air bubbles as part of the cure schedule. That work looked like me patching the hull of my sailboat.
There was like 40 megapascals of force pushing that titanium cap against the carbon fiber. That adhesive was just gap filling once that thing started down. The issue isn't going to be some dust, it is going to be whether the interface at the edges can mechanically tolerate the cycles.
@@kamilebrahimoff3589the thing is - it did handle that depth, but it could not repeatedly handle that depth. The egomaniacal fool at the wheel (Stockton) confused the two as well.
im a former professional glass fibre pipe system builder (power plants etc, 7-8years) and I absolutely agree with the issues you point out. TBH it looked that they had very little clue about what they were doing and was just winging it, hoping for the best. Also I think the different thermal expansion coefficient of the materials used could play a role.
@@thecloneguyz ..by workers wearing PSA, with a prezise construction frame to hold all parts in place by µm, measured and leveled with lasers. Direct control of the joint with Xray scanners after leaving the autoclave and and and...
I don’t think it’s an actual glue. It’s more like a filler putty as the pressure holds the body together no glue is needed that’s the way I see it especially as the fiber shrinks with compression. If it were a set bond type glue it definitely would crack and not adhere. I think of it more as a playdough type material that never cures . But what do I know it’s just a mindset. They had external collars that wrapped around to secure and seal at shallow depths as the depth increases the pressure holds everything secure. Until the hill starts cracking over and over of your expired super cheap deal carbon fiber. It was actually expired so he got it at a discount
I am a naval architect and marine engineer. I spent over 33 years working for major oil companies. All of my work was in design, engineering, maintenance, environmental issues, and spill response. I spent a considerable amount of time working on fatigue cracking particularly in critical areas where cracking could result in catastrophic failures. I have no experience with carbon fiber. I did at one point own a fiberglass sailboat. When I first heard the reports of the missing submersible and heard that it was a carbon fiber cylinder with titanium end caps, I told my wife that there was no hope of rescue. When the videos of the hull construction started to be shown, I told her that the design was flawed and was destined to fail. I agree with your comments on using a single radial wrap was a critical error. There should have been a weave pattern to strengthen the cylinder to handle the axial compression from the end caps. Even my sailboat's hull was laid up with crossing wraps of fiberglass. The Titan was subjected to multiple dives where the carbon fiber tube was subject to fatigue from the compression and relaxing of the axial load of diving and resurfacing. The arrangement of the rings and the bells leaves much to be desired. Securing the rings to the carbon fiber with glue alone, with no mechanical backup raises questions. The use of 18 bolts to secure the bells seems to be odd since a pipe flange at 6000 psi requires 44 bolts. I heard in several reports that the hatch end bell only used 17 bolts because of difficulty in tightening the 18th bolt. The lack of Classification Societies' input was a fatal flaw. Let's assume that review and approval have a zero-time and zero dollars impact. Skipping Classification meant there was no third-party review of the design, there was no fatigue analysis, there were no failure modes and effects analysis, there were no inspections and certifications of components during construction, and there were no in-service inspections. I told my wife if I had a disposable income sufficient to waste $250,000 to visit the Titanic to look out a porthole, please excuse the expression, "I wouldn't be caught dead on the Titan."
The man was an amateur, how did he get in charge of all this... the vessel at the absolute minimum should have been tested to 8k psi double the normal if I were in charge.. and I'm amateur..
When you say "pipe flange at 6000 psi" I assume you mean 6000 psi on the internal surface of the pipe? That's quite a different load on the bolts to 6000 psi of external pressure like the sub would experience.
The radial wrap was likely found to be a necessity to avoid density voids. The fibers were two directional in the tape: 90-0. They made a previous hull and it made lots of noises. This was their second hull and it was a lot better. Don't underestimate the effort they put in this... I myself thought; why not make an inner tube in metal to connect the ends, but then I realized any leakage would pry the two materials apart... What they were doing was far from easy...
The force on the endcap bond is closer to 28000 psi. ( the full surface area of the end cap applied to the surface of the carbon fiber tube) Critical epoxy mixtures are mixed by weight, not volume. Air was certainly trapped in the ring when the joint was made, not enough pressure to squeeze out the air bubbles. Also, an autoclave bond is required for high strength composite layups. I am surprised this sub lasted more than one dive.
Very interesting to hear your calculations on the pressure. I’m uncertain if any pressure was applied to the interface cap when it was bonded or do you think they were just relying on the weight of the machined part pressing down on the hill?
@@glennnovember3266 Using rough numbers for the dimensions I got similar results: -139MPa (-20ksi) for longitudinal stress. What is interesting is how they must have thought they had a margin of safety with the 0/90 layup since the resin alone was probably rated at -250MPa. I am also curious of the hygrothermal stresses of curing a 5" thick wall. This guy was definitely way off of charted territory on this design..
The mating of the titanium to the Carbon Fibre is something I've had thoughts on. Years back I used to install strain gauges in the aviation industry - mostly aluminium alloys and titanium, but also on carbon fibre. The process for metal and CF involved using different solvents to degrease the parts, and keying the surface was also a little different. The process I was taught required titanium to be warmed with infrared lamps to drive out surface and subsurface contamination like oil, during which solvents were used until the surface was clean, and various fine grade oxide papers were used to sand the surface in figure eight motion to key the surface to bonding the gauge to...which then had a light acid applied and neutralised...the process with CF was similar, but less intensive, without heat lamps. The main difference was the type of glue applied for bonding. We used a special proprietary bonding agent manufactured by strain gauge manufacturer. The CF used a different bonding agent based on a cyanoacrylate type glue. My understanding back then was that the same glue/bonding agent could not be used for titanium and CF, so was surprised to see a glue being used to mate both surfaces. Also surprised the surfaces didn't seem to be keyed - especially the titanium - ready to receive the glue! Another concern was how shallow the join was!
I've always called the deliberate roughening of a surface to be bonded giving it "tooth" - similar to how the term is used to describe how paper will hold graphite from a pencil when drawing. Absent that increased surface area, and scrupulous cleanliness, you have almost zero chance of forming any effective bond to a metal surface - and, the adhesive which you choose to apply must be to some degree corrosive to the metal in order to achieve a chemical bond. Further, you join needs to ave significant resistance to slippage, much like mating screw threads have a force resistance projecting perpendicular to the direction of tear-out. And, these slip-joints had absolutely nothing in the way of resisting elements to hold against tear-out forces. Just a bad job, physically and chemically, even before you look at the actually assembly "procedure"...
Great to hear the interesting details from your real world bonding experience. This just goes to show the length and precision we must go to do make such bonds.
Absolutely insane the carbon was only applied this way, anyone who ever 3D printed a tube knows that it breaks in the layers, this is no different, actually impressive it survived as many dives as it did.
I pictured the water pressure like an ax trying to chop a piece of wood, and how much easier it is to chop with the grain than against it. Also, since the fibers were all in the same orientation, a few layers buckling could cascade through the entire carbon fiber hull. I think the strength of the carbon fiber hull would easily have protected against implosion at least several times better if it had each layer going in a different orientation than the layer before it. Aside from that, I didn't like the fact the carbon fiber hull can't be bolted into. I would never trust diving under water in something bonded together by nothing but glue. When I first saw them gluing it together, my first thought was a massive "Why?!" It was kind of like witnessing an idiot in a horror film about to get themselves killed.
To be fair, Rush clearly states the fiber orientation is 0/90 (1:33 mark), meaning equal amount of fibers in the axial direction and the hoop direction. Still I agree that some +/- 45 degrees also would have made the hull stronger. Rush justified not having +/-45 by saying that there are no torsional moment, which is technically true. Problem is, this is only true as long as the hull is completely intact. As soon as there is a little damage to the hull. The +/- 45 degree fibers would have helped redistributing the loads around the defect. I am a structural engineer with carbon fiber experience.
@@davidosterberg how would they run a axial layer with a setup like that? Wouldn't the turned ends of the mandrel prevent them? I guess they removed the ends or there would have be axial layers at the top only???
Recent graduate in Naval Architecture & Marine engineering here - take everything I have to say with a grain of salt because again, just graduated and by far not an expert! But my 2 cents on the "strength to buoyancy" term you mentioned. My first reaction is this is the first time I've ever heard this term utilized, I also have not spent much time with submersibles as they are definitely a niche in the industry. However my next reaction is that term seems a tad bit silly since the buoyant force must be equivalent to the weight of the object (Archimedes Principle), thus in reality strength to buoyancy is practically the same thing as saying strength to weight. Strength to weight is also not really a metric used all too often in Navarc, when designing commercial ships (think tankers, container ships, dry bulk etc) weight is certainly a concern from a cost and strength perspective, but it's often not the case that in commercial design you compare the strength to weight ratios of various materials, it's just not as much of a concern since the body of water will just displace more volume to account for a heavier ship - and often these commercial ships are volume limited. In other words, commercial ships often reach maximum capacity of their cargo holds long before they're in any dangerous territory of displacing too much water. Weight becomes much more a concern when talking about high performance yachts such as the Americas Cup sailing vessels. But the usage of composites in these craft is vastly different that in a submersible... The question that still troubles me is that someone must have realized that Carbon Fiber does not have the same strength in compression that it does in tension? I wonder if the strength to buoyancy ratio he was using accounted for the different compressive strength of carbon fiber, since pressure vessels under seas have to deal with compressive loading (greater ambient pressure) while airplanes often deal with tensile loading (lower ambient pressure).
I just found your video, excellent job, my first alarm bell was the way the CF was wound one layer on top of the last with no overlap or weave pattern, you don’t need to be an engineer to see all the flaws of this design
I’ve taken a submarine design course (and used Paramarine for a project) and never heard of “strength-to-buoyancy ratio”. There is a factor called “weight limited designs” which the structure material plays into; it’s why HY80 has been superseded by HY100 and HY130 in newer classes of US subs: these are stronger materials and can thus be thinner and therefore less weight to the hull. But buoyancy has a lot of other factors not just the hull material. On the titanium cleaning clip, good catch! But based on where the rigging is laid out, it’s unclear if this would be the bonding surface or just the external surface. Either way, the controls in the entire process are COMPLETELY negligent at BEST.
No glue squeezing out of the end caps when they laid it up definitely threw a red flag for me too the first time i saw that video. Very good analysis vid 👍
Same with me, I have no idea about this technology, but seeing they place the end cap on top of the carbon fibre and no glue coming out made me nervous
@@dennisyoung4631 I'm work in a cabinet shop and another thing I notice was that they didn't even have to tap it in place it just slid right down on it
@@Blasko86 got a question for you, then. When I am putting pieces of 1/2” nominal birch plywood in slots/grooves/Rabbets/?, I commonly try for a “drop-in” fit, one where there’s (hopefully!) no needing to bang things with a mallet. (I’m working alone, still relatively new to woodworking, and am older, chronically ill, *and* disabled. Most of the shelving units, bookcases, etc. are more *disability accommodations* than conventional furniture.) I use hide glue, because it has a long open time, is relatively easy to clean up, and doesn’t leave visible stains under the finish. I then put in #6 countersunk screws. Am I full of for doing it that way? Unlike metalworking, I haven’t done it for a living, nor did I take college-level machining classes. I did my share of reading, and I have asked people about it who have more experience than I do.
I hear Rush patented his “real time hull health monitor” system. He also said in previous dives the cracking was loud and persistent. Since we know that cracking sound was the sound of a hull progressively weakening, his monitoring system was obviously another useless idea.
I’ve have no expertise in these things but it seems like cracking sounds equals damage. Damage that can’t be properly repaired or even evaluated. To continue to use something you know is damaged for a mission that dangerous is insane.
▪ _"A former OceanGate finance director said Stockton Rush asked her to be the head pilot for the Titan."_ ▪ _"She told The New Yorker_ (Magazine) _that she quit when the OceanGate CEO urged her to replace the former pilot."_ ▪ _"The pilot, David Lochridge, previously said he was fired for noting concerns about the sub's safety."_
Reading this after Antonella and Lockridge's court hearings shows that we all knew what lead to this when it happened. Now, all we are doing is trying to reconstruct the implosion to see when it happened, at what depth, and if the passengers knew it was coming.
@@theseatownfunkpodcast1332Ironically, even a third grader can see how childish it is to make a jab at a random innocent person's grammar for no reason.
I think the problem was the difference in stiffness between the carbon fiber and the titanium end caps. Under the pressure¸ the CF cylinder would have compressed in the radial direction much more than the titanium ring. This would lead to radial shear and bending stresses in the glue joint.
There were just so many pathways to failure, about half a dozen that seemed inevitable. Various things to go wrong in the bond, same in the layup. Rush really had a psychological blind spot in his intolerance for criticism.
As a materials engineer, the difference in modulus of elasticity between the titanium and composite seems like a likely cause of failure here. Computer modeling was likely used to calculate the stresses involved, but there can be many reasons for adhesive bonds to not meet the properties listed by the manufacturer. Consequently, extensive testing of the bond should have been done before risking human life in the vessel.
I was thinking this too. Seems like you would want the more elastic material on the outside so pressure increases the bond rather than pulling it apart when it's inside the titanium.
Kudos for the slide discussing the necessity for surface preparation of the titanium for adhesive bonding - that's better detail than I've seen in any of the other discussion to date.
I'm skeptical about the emphasis on the glue, although it is certainly indicative of an overall sloppy attitude to quality control (and health and safety). The external pressure will tend to push the end caps harder onto the carbon fibre tube the deeper the dive, closing any voids without putting any sheer load on the glue. Since the pressure increases progressively during the dive any water leaks through the glue interface should have been apparent before they became dangerous. The carbon fibre tube may well have compressed more than the titanium ring, but the latter seems to have an internal channel the inside edge of which would have broken off if this were the root cause of the failure. My money is still on a simple and entirely predictable fatigue failure of the carbon fibre tube.
The hoop stress means this carbon tube is gonna shrink in diameter. If the titanium shrinks at a different rate, massive shear stress. Temperature changes can result in insane shear stress. I did a simulation on a pool window of poor design: 300,000 lbs due to thermal stress alone
@@ZebraLemur However, as I said in the OP, it is not a simple butt joint. The carbon tube is glued into a channel in the titanium ring. Under the strain you describe, the inner lip of this channel would be stressed and would have to break off for there to be significant movement of the glue joint. The titanium parts seem to be completely undamaged in the images we have seen. Conceivable that localised damage was deliberately or accidentally hidden as the parts were lifted ashore, but it will still be known to the investigators and should resolve the matter one way or the other. The fact that the carbon tube has not been recovered, or even significant intact pieces of it, also argues for this as the original failure.
Yeah but you're not thinking about the fact that the carbon-fibre compresses at a different rate than the titanium and what would that do to the mating surfaces?
@@thecloneguyz mating surface - nothing good. Just saw another video on this sub where a professor from Europe runs modeling software on this vessel under pressure. That model of the failure looked like the Pringles can being squeezed, everything was over in just a handful of milliseconds. The highest stress was at the Ti-CF joint. After the joint failed and the cylinder shattered the two titanium end caps were driven inward at high speed and ‘clapped together’ in the center where the cylinder used to be. After seeing this I have now come around to seeing the Ti-CF joint as the biggest problem. No matter what the adhesive or procedure used, this joint is the location of the highest concentration of stresses. Since there were several successful dives to this depth before this incident, material fatigue cycles must have played a role. Perhaps the glue joint finally failed, or the carbon fiber itself became weaker and deflected more on this dive, or both, or something else (he also identified the acrylic window as a weak point). The titanium hemispheres that were recovered looked brand new from the brief unloading video.
If there’s one silver lining we get out of this, it’s that hopefully many composites professors and industry SME will use this as a warning to future engineering students. Similar to how Tacoma Narrows Bridge is well-known and taught in the engineering community.
Don't hold your breath. It isn't like engineers didn't already know ALL of this before the sub imploded. Some of them even tried to warn them. Still, they did it anyway and killed 5 people.
@@stargazer7644 We all do because we have experience. I'm talking about professors teaching new engineering students. I see how my OG comment didn't make that clear. Edited. It's a big event people know of that they can use as a starting point to a set of lectures.
I don't think this is really comparable with Tacoma Narrows. Tacoma Narrows was, as I understand it, a bridge that failed because we didn't know you need to consider XYZ when building a bridge (specifically, the possibility of aerodynamic flutter causing resonance). Its failure taught us lessons that could be incorporated in future suspension bridge design. Titan's failure seems to have been caused by ignoring things that we already understand well. There's no lesson to be learned, because we already knew not to do all that stuff. Unless your point is that now there's a practical demonstration of what happens if you ignore these things.
For generations to come, videos like these will train future engineers how NOT to design a submersible. Good job Sir, in training us laymen on complex engineering subjects.
I hadn't thought about that! This wreck is the 'How NOT to build a submersible' like the Forestall (or 'Forestfire' as my naval friend says), is the standard video on how NOT to fight an aircraft carrier fire.
Unfortunately these findings are nothing new, similar things have repeated in the history over and over again. What we learned from this: RTFM with materials&glues etc and let certification people do their work and go through everything or work with them to establish best practices to ensure safety.
@@nadagabri5783yes, I'm wondering if someone could of sent a lawyer or a letter to Everett Washington explaining the dangers and get the occupational license revoked so they couldn't operate. This could of caused unwanted press coverage for oceangate and exposed them before a tragedy could occur..
YES!!!! thats exactly what I thought ,like here ya go dad ill hold it up for ya then we've finished up we'll have beer whadda say hey ...bloody madness
It's horrible. No hair nets, no face masks. I seriously doubt the glue was homogeneous at all. And they didn't even degas the glue. Seriously, with the cost of epoxy, I take more care doing a small project than these guys. It's clear they didn't care. The guy with the dirty rag... It's titanium, right? I'd assume you would wash the area with some solvent so it's absolutely debris free. I'd want to be in a Hepa filtered room, but if that wasn't possible, I'd wear a hair net. When you put a semi-liquid surface, there's a tool that tells you the actual depth of the stuff (usually paint, but works with glue). In other words, people painting industrial surfaces take more care than these guys did building a prototype submarine. But they seem to be mixing it glue by hand in tiny flimsy containers.
Excellent video. However, the biggest problem is that carbon fiber has a much lower modulus of elasticity than Ti. The tube wanted to shrink by 1/2" at depth, but the Ti wouldn't let it, resulting in an ENORMOUS stress concentration on the inside of the tube at the junction of the Ti, resulting in buckling.
It's now 9 months later and I still find myself digging for more quality Titan content. I have no relation to the sea, diving or engineering and have zero understanding of why I'm STILL fascinated with every angle of this event. Really good content btw! A+
Im the same im a 57 year old woman who is into poetry and music and yet I find the whole thing fascinating.Stockton was magical in his need for ego accolades ,if he wasn't he would have done everything with expert care and precision
"Squeezing a can of Pringles" Exactly the analogy I've been using to explain to friends that the Titanium rings overlap with the CFRP was way too short.
I don't agree completely with that analogy, because it implies the initial failure had to be radial. However, don't forget that in the sub, there is also an extreme amount of pressure on the end caps pushing in, thus reducing the need for much ring-tube overlap, and I suspect the initial failure was the tube itself in axial direction, not radial. And the reason for that, is the 1:3 scale model Oceangate tested to failure. You can see a picture of it at 3:46 The tube is still round, it's the end that is pushed in, delaminated/shattered and has separated from the metal end rings and caps (not in the picture). So a better analogy could possible be that you take a Pringles can and stand or jump on the lid so the tube buckles/shatters, and not the other way around. And if that was the cause, it would probably not have made any difference if the ring-tube overlap was ten times longer.
@@AORD72 We have to assume they did some cycling before full pressure to collect more data, especially since they made a big deal about the so called "real time monitoring" system that would detect abnormal movements and acoustics in the hull, that would change from one dive to the next dive, and that the scale model had fitted some of these sensors, but I can't say that for certain. Stockton only talk about the scale model test very briefly and doesn't specify it any more other than they took it to failure and the shockwave blew out all the pressure sensors in the chamber. They did the tests at the University of Washington so there should have been at least some smart people in the area...
It feels like Stockton was just guessing. Had some interesting ideas, implemented them haphazardly, cutting corners, didn't test them in any way, ignored warnings, and just YOLOd it. It wouldn't have been so bad if he was just risking his own life, but he also convinced 4 others and took them down with him.
People are allowed to think before going with him. He wasn’t forcing anyone. Like getting in a fast car with someone who says it will all be fine but there’s always a risk. And even someone without knowledge in engineering could see this was made to fail
@@PT-mj3bktrue. Problem is he probably didn’t properly convey the actual risks. When I went skydiving, I also had to sign a bunch of waivers and consent forms. The company still had a responsibility to provide a safe experience - if the instructors were inexperienced, planes and equipment poorly maintained, corners were cut, etc., I would have had no idea. I simply knew their track record was good (no deaths in over a decade) and trusted the company. Oceangate depended on these paying customers and Rush made all sorts of misleading claims about the safety of the vehicle and went out of his way to convince clients (e.g flying to meet with them) - it’s impossible as a customer to accurately assess the risk if the company is dishonest.
@@sue8412 Yes, and to add to that, Stockton claimed they collaborated with NASA, Boeing, and U Washington, but that was a lie. Stockton was also warned by his own employee as well as external experts about his fault design, but he ignored them.
@@PT-mj3bk A better fast car parallel would be if the driver failed to tell you the car was improperly maintained and that it had had some issues on previous rides that were brushed aside. Also, the car is not actually road safe, but the driver failed to mention it. Also, in case of a crash, the airbags may or may not deploy, but the driver also forgot to mention this and other details that are necessary to make a fully informed decision.
A quick search and we find that the 'circumferential' stresses are double that of axial stresses in a 'thin walled cylinder'. But I've also found that so-called 'transverse' strength of carbon fiber is a lot less than when applying along the length of the fiber. So even if there are no 'torsional' stresses, certainly there are axial loads, and being applied perpendicular to the fibers. That seems to be a BIG problem (IMHO).
Right? Painting a car: every surface is prepped and meticulously wiped down to get rid of every spec of dust. Paint is sprayed on in a paint booth that has an air filtration system by techs in full body suits. And then there's ocean gate mixing up batches of glue by hand and applying it the same way in what looks like a dirty industrial facility.
Even if there weren't any air bubbles entrained in the adhesive during mixing and application, there would be microscopic gas bubbles formed by the leaving groups coming off of the monomers as they polymerized to form the join. Normal procedures to remove these bubbles include curing at elevated temperature under vacuum in order to draw the gases out of the adhesive.
My experience in the chemical industry is with using Fiberglass Reinforced Plastic piping and tanks. The glass fibers give strength to the composite when in tension. For a cylinder, tension of the shell occurs when the pressure is on the inside (pushing outward, i.e. attempting to deform the cylinder into a larger diameter). The glass fibers resist this tensile force by not stretching, like a rope wrapped tightly around a pipe. When the pressure is on the outside of the cylinder, the composite is under compression, which the fiber reinforcement really does not help with. Here, the structural strength is provided by the resin, a thermoset resin, i.e. a cross linked totally rigid non-plastic material. It does not yield like a metal under load, but rather cracks microscopically each pressure cycle until the structure fails all at once. I agree that the end glue joints to the titanium were riddled with problems. The biggest problem that leaps out to me is that the whole cylinder relies on resin for its strength, resin being a type of glue itself !! I am interested to hear from folks who have experience with both carbon fiber and fiberglass in compressive loads. Is the fiber reinforcing principle the same or does carbon fiber have additional properties that would help it in compressive loads?
if the composite had been formed with 3-d cf, it might have survived - worked well, even. But principally 1-d circumferential, eh?? The wall stress within the cylindrical hull main body would also not have been in pure radial compression, the end-caps would be applying (very approximately) 1/2 the radial stress, but in the z-direction - i.e. along the long axis of the cylinder; the cylinder was therefore in triaxial stress - was this accomodated?
@@jesflynn4048 thanks for the insight. I’ll have to look up 3D carbon fiber, sounds like exotic aerospace. The loading on the end caps you mention is another compression load, perpendicular to the CF fiber winding direction. In this direction the fiber provides no reinforcement strength at all, just filler. I looked up the deep sea expedition by Victor V. His submersible is named something “Factor”. He did it right: designed and built by an experienced submarine company, pressure vessel 100% titanium, and they actually pressure tested it to 120% of max depth. It worked great.
I've worked with carbon fiber and fiberglass! They are totally different critters! My experience that glass doesn't compress, but carbon changes character when compressed at different pressures and heat! Where do you think diamonds come from? I've worked with HYDROCLAVES working at 3,000 P,S,I, our carbon "cloth" turned into graphite! It works great for boats or aircraft.!
This was a really thorough, informed and thoughtful analysis of the various problems with the design and manufacturing of the submersible. I'm not an Engineer, rather I'm a physicist, and some of these issues seem disappointingly trivial, even to someone with my lack of relevant knowledge and experience. Not correctly texturing the surface of the carbon composite and/or the titanium dome before bonding the two... From Year 7 D&T I can remember being told to rough up surfaces a little before gluing things together, give the glue something to grab on to.
I saw all these things in the video, it was surprising so few people picked up on the cleaning of the titanium rings for instance, I put signs together and if I saw one of my staff touching the surface before the VHB tape was bonded with bare hands I’d be very upset and tell him how to do it properly and that’s just with street signs!. I don’t want them coming off the posts in a high wind and killing someone. These people didn’t even seem to understand this most basic concept. Again, as you saw, no glue coming out of the join when pushed together = no glue on the join. Also try sticking two perfectly flat surfaces together with glue, can’t be done properly can it, there will always be massive air bubbles. Go on, get two sheets of glass, hand spatula glue all over both sides, offer them up to each other almost completely flat and you know what you will see when you hold them up = Massive air pockets, not just bubbles but air pockets!. How could this person call themselves an engineer? What stupid exams did he pass to get his qualifications without the slightest understanding of how materials work. I’m just a sign manufacturer and I get it. Also at the most basic level I understand the difference between compressive strength and tensile strength. Not one of their engineers did. The only thing holding that thing up under that pressure was the strength of the resin, not the strength of the carbon fiber because carbon fiber is “only” strong when stretched, not bent or compressed.
Hi, I'm an engineer who has worked on Racing and custom Bike applications, using carbon Fibre parts. I had many reservations about using or making carbon fibre parts, after watching many catastrophic failures during the early years with mainly wheels being the parts. They would suddenly disintegrate on track, after looking perfect in the pits, just before they left, not hard as they were all practically new items. All the parts required bonding to Metal machined parts usually aluminum or Titanium, which would then be Bolted up, using either steel or Titanium studs or bolts to attach the other parts. It was found that Carbon Fibre had Die-electric properties of its own, and as a result acted as a dissimilar metal if Bonded directly to the Metal part using carbon fibre parts, after a couple of uses for let's say a front wheel with an aluminum hub, which was then bolted to steel front disc rotors, would advanced corrosion that could be seen upon disassembly, and the same could be seen where cracks or separation had occurred at the carbon to metal interface. This was remedied by coating the boned metal part in normal fibreglass resin and then applying the carbon fibre layup to that while still tacky, or when dry machining a course surface into it. Now true the forces we are looking at are completely different from the mostly compressive force you are considering, but after seeing the same video you showed in your explanation when this occurred, it didn't surprise me at all to see the interface come up completely clean and free of any distortion. To be honest, that was exactly what I expected to see actually, if the Boned surface had held at all, with the way it was constructed I would have expected to see at least some stands or parts of strands still dangling to it. I expect, and would suggest that at least a few of those cracks or bangs were at least in part, the carbon-to-metal interface separating until when "Loaded" with 5 people on board it finally separated completely and cleanly, leaving the hemispherical bell at each end as manufactured, not deformed? I expect it was the forces from the implosion that blew out the observation window. I'm really sorry for the other people on board, who were conned into going down in this thing, the whole thing was a sad Joke! Continuous monitored settling cracks? even this supposed "safety system" was a Farce what exactly is acoustic measuring going to do for you, other than annoy you just before or while dying. What this so-called Engineer, did is tragic, and the very reason we are professionals with demonstrated safety factors in place for a reason. I've worked for two Major companies on pressure vessels, with pressure, being both positive and in a Deep vacuum. I've also been nearly killed and was finally seriously injured, due to a like employer. Despite a multitude of written warnings and a year-long refusal to work further on this project, regarding safety limits concerning how the initial load was applied, rather than a gradual build-up as designed, it had become an instantaneous shock load, and it failed exactly as predicted throwing a 500lb endbox thru the air over the Machine and Control panel were I was standing and it struck me on the shoulder. This kind of Engineer gets us all a Bad name? and his victims Killed and injured.
Thanks for your great comment and insights into bonding metal and carbon. Great to hear some real world industry experience. Very sorry to hear about your gung ho employer. I fear there are far too many folks out there like that pushing the envelope too hard, too fast. Fine if your putting yourself at risk as the only end user but not when it’s other people’s lives. Hope your shoulder has recovered well!
Sorry for your injuries! I reminded me of a similar situation that I was in! - working with composites. I was lucky and escaped the explosion, just in time! I warned my fellow workers, who at the time thought that I was crazy! We all eventually escaped without harm,, when they saw I was serious,! To many engineers think because they got a better education, they are above reproach and are superior minded!
@@robertchilders8698 Yes, watched it Happen as the engineering profession was revamped, as their goal is more prestige and the ability for connected Burracrats who just happen to be in Engineering rush to get seats where they'll never have to be an Engineer again, just administrators. I could write a book about the cock-ups and Deaths these idiots have caused, during my career, being that I've worked at most levels. I had to go Find a friend's corpse once, that had been left to stew in the cooling Tower pond over the weekend, due to the layout of the plant, and the Machines being up on a catwalk, over the pond. He was carrying out a yearly inspection, I'd been there with him on Friday when he placed all his Lockout padlocks on our Breakers. Meanwhile, some cocky Maintenance Engineer had decided to use an extra set of contacts going spare on this Machine to Bring on a pump, he never thought about this situation. He needed the pump for process, so it could run with the other Machines we had 6 there. So He ordered someone to cut off the Lockout padlocks and turn the power on while they temporarily got another feed to the pump, He Killed our Guy a Family man with 3 young kids, to his death, to save face for an extra 5 minutes. He stated that he had told someone to go tell our guy, But it never happened and as my Help wasn't needed again till later, I was sent to another emergency as it was summertime on a Friday afternoon. Honestly, I have enough to fill a Book, including my own. This is one of many examples of this, where the project was completed without the Machines ever leaving the loading Dock or even the street in one case, Cop's Coliseum, Do you Know How many people must have come and gone and said something to him about Missing Machines? Once in London, the plant room was at the lowest level of the underground parking, The Building was like a Lifesaver shape, a Hollow circle, They had to smash open all that rebarred concrete and then we Dropped the Machines in through the Top, $500,000 a pop for the machines then all the services to hook them up, electrics, plumbing, welding. Instrumentation, pumps sensors, Microprocessors enabling the building control, All there, doing nothing, I'm only supposed to be there at the end to inspect all that work and or troubleshoot if theirs a problem, and remedy it, regardless. and turn everything on making sure it reaches Design parameters, How does someone who is supposed to be a fellow engineer, walk past the Machines every morning and not clue in ? It's amazing and these are the Guys rushing out of Universities, who have never seen a bloody thing until they get a Job, and then they are suddenly managerial Material, My old Boss was ex-Navy when I was going through my Qualifications and Training, He would have punched your lights out, then depending on circumstances he'd have decided if he was keeping you on or not. In those days getting let go, mid-training or just after was the Kiss of Death, yet I know many of these never even got a reprimand. On the Sub, it shows this Kind of thought, who else would design a WARNING system for about to die or dead? Regards Ian
Worked for an adhesive manufacturer. With adhesive, less is more. Firstly, there would ideally be a primer applied for the adhesive to 'key' onto. The bond line needs to be thin and consistent to get the best surface/surface to contact. Applying by hand with what looks like a tile spreader isn't going to be very constant, and will lead to an uneven bond-line, introducing weakness in the adhesive bond. Should be applied by robot to get consistency and the correct bead (similar process to a car windscreen).
Excellent point about fibre orientation. Single direction creates perfect path for cracks progression. I guess this is the key design flaw. Picture in 2:45 is showing perfectly what probably happened.... 👍
It also strikes me the carbon strands at the ends of the tube will be irregular where the machine laying it on the tube former changes direction (eg at 2:16). There would have to be some bunching of the carbon fibres on the inside of the bend formed as the head changes direction because of the width of the tape. There would also be some inconsistency as to where these bends lie on top of each other, just where there are the loads transferring the axial compressive forces from the titanium ends onto the tube. I guess the idea was that the resin glue would spread the load, but it does look to be an area where repeated loadings would lead to settlement and cracking.
Very interesting hypothesis, I also believe the interface joints failed causing catastrophic compression. The two dissimilar materials definitely pose a very high risk of separation at the pressures experienced at that depth. I've seen pressure tanks for SCUBA made of carbon fiber, which are lighter than their metal counterparts, but are limited in their number of pressure cycles. It will indeed be interesting to see how future test and experimentation allow carbon fiber to be used in future under sea exploration. Very well done video on your part.
Bonding area is pretty important and a tapered sleeve on outside with 3-4 x the overlap would have possibly preserved the bond. However he mentions not seeing any bonding agent squeeze out....When we bond and pot things with thickened epoxy a real problem is when you slip one thing over another or inside another, you scrape the glue off the sides and push it into the end which also traps air. The ends aren't even touching 100% . You go back later for a repair and cut through to inspect and that is what we see.
Most deep sea vehicles are made as a sphere whereas the Titan was a cylinder but I have not read much about the difference of how a cylinder would act under extreme pressure compared to a sphere, the shape of the Titan may be part of the problem as well as the materials and construction methods.
7:00 An extremely good point I haven't heard anyone make yet, any air in-between those mating parts would have collapsed to nothing possibly breaking that seal in sections and putting undue stress on the carbon fibre parts and possibly introducing torsional stress as one section of the hull flexes more than the opposite side.
If they used any kind of micro balloons to thicken the resin, it would contain small amounts of air that could be compressed Rescue bueys on atomic submarines were made with phenolic micro balloons that were good to down about 3,000 feet!??
5:39 I noticed the guy touching the parts after wiping it with a dirty rag too and 9:30 no glue squeezing out, I almost had a heart attack when I saw them gluing them together. No thank you, No way!!!! You're crazy i wouldn't go 10 meters in that thing !! And to think they thought it was good to go bring on the paying customers.
Extremely interesting including the comments, with people of different areas of expert knowledge contributing. Shows one reason why we have specs, so that the knowledge of different areas can be collected and applied. And why him refusing to be certified was such a folly.
Not only the compression properties ( as opposed to expansion rates ) of the three components, but more importantly the distortion. The carbon fiber hull will begin to distort into an oval, whereas the titanium ring will distort out of true, the bonding between the two will have to “stretch”. This certainly explains the “cracking” sounds heard. That is the point of failure, allowing high pressure water (6000psi) to infiltrate the joint and act as a hydraulic wedge instantaneously pushing the two surfaces apart. Failure is highly predictable and catastrophic. Working as a senior structural engineer for Lockheed Martin within the Marine Division, this very phenomenon has been studied and documented repeatably. It s disturbing that any research Oceangate did, they either didn’t access the available data or discounted it.
Note: The guy wiping the ring down with a shop rag appears to be removing stray dust from the opposite side of the parts from the actual bonding groove. This is also a necessary step, as stray dust can migrate as the part gets craned up and over the CF cylender... hoever, he's not wearing a "bunny suit" and thus can leave skin cells and hairs behind after wiping down. Not a good situation on the non-bonding surface, but definitely a poor practice indeed on any surface where you want to achieve a bond.
In a cylinder, pressure (internal or external), will be two times in the hoop direction (circle around the cylinder) but one in the axis direction. For rockets and internal pressure you either add end to end loops or use a 27 degree “magic wrap angle” which provides needed end to end strength without giving too much hoop stress. I heard that there were layers of multiaxial carbon fabric added by hand in between the zero degree uniaxial wrap. But haven’t seen documentation.
Very interesting about that magic angle. I do wonder if a design more like an internal pressure vessel, would have done much better over time. Will be interesting to find out if any other axis were used…
I'm not an engineer. I'm just your average layman. When I watched a video of a guy hand spreading the epoxy resin to bond the carbon fibre pressure vessel to the Titanium end cap in what looked like an open-air hangar facility, I was incredulous. It struck me as amateur and didn't make sense, especially given the depth that the submersible would be diving to. I imagined that the interface between the two materials would be really important and therefore would be treated as such and not undertaken in such a casual manner.
You've pointed out some of the questions I had about the carbon fiber section. The two part epoxy applied with a mixing nozzle, reorienting the fiber direction in subsequent layers, and proper surface prep should have been no-brainers. I have yet to hear anything about how the carbon fiber section was cured. Aircraft industry standards for curing composites is to bag the part (on the mandrel) and apply a vacuum inside the bag to compress the layers before and during oven curing. Overall, it seems either shortcuts were knowingly taken, or someone didn't know what they were doing. But what do I know...I'm just a 68 year old white guy that worked in manufacturing laminated aircraft components (including heat forged carbon fiber airframe connectors).
Finally, a well documented, balanced video that doesn’t just go “carbon fibre is bad in compression, that’s sooo obvious, these guys are dumb, brrr”. I’ve recently watched video from real engineering and was a bit disappointed in that regard. But your vid point exactly to realistic potential sources of failure. Well done!
I’m so glad someone brought up the ‘carbon is bad in compression’ trope, I feel it’s thrown around a lot without. Whilst it’s true it’s only 30-50 % of its tensile strength with proper fibre alignment one can mitigate the disadvantages a fair bit!
This is the best video I've seen so far because you are looking at specifics, not just criticizing Rush for a lack of concern about safety. My guess is they just didn't have the budget for a proper job, whatever that might be.
Thanks for your professional input on the matter. My cousin, who professionally fixes yachts, said a similar thing, just with fewer details and with a lot of swearing. I use home made carbon/kevlar composites only for fixing RC toys. Before I touched the stuff I watched about 40 minutes of tutorials on Easy Composites website and without the slightest exaggeration I'm way more qualified to fabricate composite parts than any of those Ocean Gate engineers.
I’m okay with people taking their own dumb risks for exploration or sport. We don’t make wing suit athletes certify their wings. But OceanGate better have been very very thorough and honest with every design detail in their marketing etc before they had those people sign wavers. If you’re up front and honest about the risks, I think people should have the right to do stupid things like this to an extent. I feel bad for the kid though. What an irresponsible father.
It didn’t have to because the submersible only operated in international waters and was carried through territorial waters as cargo on the deck of a ship. By operating only on the high seas and not being registered in any country, it was literally outside the law. Rush deliberately chose to operate it only in international waters because doing so meant that he was literally outside the jurisdiction of any country.
I have 28 years experience in the middle east as technical manager in composites, and agree with you that the bond between cf and titanium was a question mark. For me, i will never introduce different materials for this application and compensate with a huge value for manufacturing constant not less than 10, and a value of 3 for cyclic load constant..Also, i agree with you, he should have placed layers of helix winding. Filament wound should be one-piece such as this kind of application.
It's just astounding how many mistakes and corners were cut by this guy. Strength to Bouyancy is horse-quaqamole. Buoyancy isn't what kills you at 12,000 ft, its pressure. I'm amazed this thing actually held together for 10 other trips. Mr Rush was truly a "baffle them with bullshit" and "smoke and mirrors" engineer. Its shocking and sad people paid good money and risked their lives with him. Informative video!
1:38 Rush says the ply orientation is at 0/90 which covers the axial and circumferential stress (2X axial). It’s not a single fiber orientation which is repeatedly mentioned by the narrator. I’d also be curious what the preload on the end rings during bonding. The adhesive isn’t under the usual tensile and shear stress either since the structure is under compression and the adhesive stress is mainly due to poissons stress. The lack of excess adhesive is less critical for this type of joint stress.
I think that this is the best analysis of the OceanGate sub. And the only one that I've seen that's placed any attention on the bonding and process and the fact that the titanium ring was recovered with not a bit of fiber on it.
When you hear the guy talking about and wondering, and almost bragging about just 'How far out the box' he is operating, it makes you feel sick that he could do this AND take others with him AND charge them a quarter million dollars at the same time. He will be remembered as one of the worlds biggest Wankers
Great to see some knowledgeable, objective discussion - thanks. Hadn't heard Rush saying "no torsional forces" but as someone who has spent a lot of time in small composite boats in tidal waters, this doesn't ring quite true to me. If you consider a dive in a swimming pool, the predominant force is indeed the compressive water pressure. However, the ocean is a much more dynamic environment. From tidal streams near surface, to the deep ocean currents moving vast distances, a diving sub may potentially cross many interfaces where the water on either side is moving in different directions. In addition, they towed the sub on its raft out to the dive site. The raft will have protected it from the stresses of bridging between wave crests, but depending on weather it may have been subjected to irregular wave impacts. I don't know the relative magnitude of these forces, but I doubt they should be written off as negligible. Even if each instance is not overwhelming, surely they would have a cumulative effect? Willing to be corrected if wrong! (Re layup: even our small carbon fibre boats are vac-bagged!)
The carbon fiber and titanium have different compression strength and behavior. While they seem snug during the construction, at depth there would be a small but significant difference in the diameter of the fiber cylinder and titanium ring which would put a lot of force on that little layer of epoxy. I’m surprised it lasted as many dives as it did.
I am an electric / electronic engineer, who worked for decades as a commissioning engineer for high-tech vacuum coating machines, installing and repairing them on all continents. 1. When I saw the toy play station controller, it was clear, they also skipped any industrial (not to mention submarine) standards. Electric / electronic components within a ship should have at least a certain degree of dust- and most importantly water-tightness. If there is some slight leak within the ship, water might just start to drip onto these components. But water should never be allowed to come in to keep things controllable, even if it is just for the emergency routines. It is also important to avoid internal fires and electrocution of humans. Our factory-based = land-based industrial machines have watertightness requirements (like higher IP-categories) when electric / electronic devices (sensors, valves, etc.) are to be assembled i.e. in or near water-cooling circuitry for the very same reason. 2. When I saw all the spaghetti-style power- and control lines (electric, air etc?) on top of this wacky "submarine" without any mechanical protection against whatever might come along, I knew these "engineers" are just charlatans. How can you keep control lines of any kind in a rough environment like the deep-sea so exposed? There might be so many unthinkable objects or perhaps large fish / whales bounce against it or get entangles there, i.e. while cruising around a huge rusty ship wreck or being lifted in and out of the waters. It is amazing to see such extreme thoughtless botch from thousands of km/mi away through shaky TV-cameras. The BS-phrase of "thinking-out-of-the-box" became obviously a complete new meaning or "level"; I personally rather stick to my profession and keep thinking inside the box - for safety's sake of the people operating "my" machinery. Just by looking at this "submarine" (before it imploded), I would never have put my butt into it. Any old lawn mower feels more safe. Peace! from Dresden / Germany
CRP is still a sort of mystery material today. I've been in aviation manufacturing and we don't know exactly what it's hysterysis/longevity really is. And that's after 40 years.
I spent 30 years in the composite business. I have filament wound structural members. In glass and epoxy resin. We used two types windings Circ's which was similar to what he used. But we used a winding called Helix on every other layer. And the band end to end with like one revolution. That entire layer was like basket weaved for a complete layer. Then another layer of Circ's to pull everything together. The Carbon to resin ratio is also important to dry and things pull apart, to wet and it becomes brittle. Bonding the titanium end caps didn't bother me as much as the winding pattern did. Just my opinion.
Intuitively, carbon fibre going only one direction seems like a terrible terrible idea. I realise the primary strength will be going around, but that leaves no room for error if any part is weakened a bit.
The primary strength will be going around IN TENSION. Carbon fibers are like wet noodles, they have no strength in compression. The only strength here is in the compressive strength of the resin.
@@stargazer7644 wrong, they're not like a "wet noodle", the compressive strength can be up to 50% of their tensile strength. Also, the epoxy holding them together has great compressive strength.
@@xpusostomos Carbon fibers are THREAD. You can hang your car from a single 1/4 inch carbon fiber rope in tension with well over a 2 times safety margin. So you're telling me you can balance that same car upside down on the end of that same 1/4 inch rope in compression? Have you ever actually handled carbon fiber fabric? Carbon fiber alone has almost no compression strength. In a composite the resin is just about the ONLY strength carbon fiber has in compression. Using carbon fiber to make submarine hulls is like using concrete to make tubes for pressure tanks.
@@stargazer7644 There is much you don't understand. Firstly, the sub wasn't made of carbon fibre cloth, but strands of fibre, all going the one direction. Secondly, to make a tube lose structural integrity by pressing on it the inside of the tube would be under tension while the outside would be under compression. Thirdly, the compressive strength is measured when the fibres are in alignment with the force applied. In a rope under tension, they are kept in alignment by the tension. Under compression you've got a problem keeping those fibres perpendicular to the force. But the sub is not a rope trying to hold up a car. Fouthly, carbon fibre has about 4x the compressive strength of steel. So let's say you wanted to support a car with some material by compression. What's a good material? Most people would say steel, that's what every car lift is made of. That's what every set of car ramps is made of. And yet carbon fibre is 4x better. Fifthly, don't listen to me, use Google and find out for yourself.
Saw this I think on Reddit. One reason SpaceX switched from carbon fiber to stainless steel pressure vessels (fuel tanks) was the difficulty of detecting structural flaws. I'm a lay person but my father is an architect and builder of skyscrapers who also went to Princeton only years before Stockton Rush. The federal regulations and codes in the construction industry, especially high rises, are insane but are very necessary. I'm sure the "crackling sounds" they heard was that carbon fiber breaking up! What else? Or those seals coming loose or that damn Plexiglas porthole that was inches too thin. Stockton was always talking about people in the deep sea exploration community using a "safety argument to disrupt innovation." The problem is you can't argue with time tested engineering and physics. If you're going to use carbon fiber, it must be in a woven pattern, not a single weave. That isn't strong enough. And that video of those guys applying the glue? Why weren't they using an autoclave? Wearing gloves? It's insane. That thing was built by students who had no idea what they were doing, lead by an arrogant greedy man who skimped on materials and had no regard for anyone else's safety pr lives, not even his own. It's all very sad.
Very good analysis of what and why likely happened the Titan implosion. Thanks. IMHO it's even intuitive that the carbon fiber layers should be put ALWAYS in several (many, even some layers at random?) different angles to get all its properties, strength and to diminish the advance of delamination and its speed of propagation. The RTM that Stockton included into his carbon fiber submersible was a good idea (indeed as per the transcript, it took about 19 minutes since the moment when the RTM alerted something was wrong with the carbon fiber hull to the moment of the implosion). So, if just he would have laminated the layers at many different angles, likely he had time enough to save the situation. Also, it's pretty clear that the delamination was already quite advanced since the beginning of that last dive because it descended faster than predicted (and yet faster as the submersible was diving deeper) and it then did ascend very, very slowly despite all their efforts, which was "unclear why rate is small" (I guess due to the delamination the carbon fiber hull was being compressed, deformed and so bending slightly and more towards the mid section of the tube, firstly silently, then loud enough for the RTM to note it and, finally, with terrifying bangs and cracking sounds...). As the hull starts to give in to the pressure and bends inwards, it displaces less water, hence it loses buoyancy. The carbon fiber composite is very hard and light material... but fragile when its limit is exceeded. So for submersibles, even being well constructed with carbon fiber, I think it's better to rely on other materials which are able to deform without cracking, like high quality stainless steel. And also the shape it's very important. Needless to say that the sphere is the best shape for this task. But, the shape of a rugby ball it's better than a cylinder shape (because the arc shaped structures are much more robust than the straight lines) as it's so widely used in construction of dam retaining walls and in architecture.
Being in carbon fiber since 30 years for racing purpose, when i saw how they just wound the carbon on that tube without making a cross wound that allows resistance of both axis i was flabergasted. At the two tube ends the resulting pressure from the two caps are is applied only on the tube end surface in a direction that the wounded carbon fiber give no resistance. So in this way only the matrix resin can hold the pressure and will cause a quick wear and of course the bounding is also a problem. But you have to keep in mind that the glue doesn't hold the caps, the water pressure press so hard that without any glue in would hold. Just look at how the two caps are bound to the two titan rings, just a few little bolts to keep it toghether. The problem is that the carbon made the way they did it gives no resistance in the tube axis and then nothing keep the wounds together except the resin, this is nuts!!
Nice to hear from someone with experience in carbon fiber composites. (CFCs) - titanium construction. A couple of questions come to my (4 year mech eng degree) mind. (1) water will seep into any tiny pore or crack due to capillary action. What is known about water at 5500-6000 psi forcing its way into tiny cracks of the resin matrix & promoting delamination or such? Or would the compressive stress tend to close the cracks? Maybe no one knows the answer since most deep sub manufacturers want nothing to do with composites in their pressure hulls. (2) I noticed what looked like a step in the circular edge of the CFC cylinder, that is, a reduction in diameter from the main wall down to where the Titanium end caps/rings are glued on. To my mech eng mind this screams out “possible stress concentration” which is double deadly under cyclic load. Are CFC subject to stress concentration due to changes in section (or notches) to the same extent as metals? The edge may be designed with a proper radius (or not) I can’t tell watching on a tablet.
Physics does not care what material it is concerning stress concentrators , section changes, material changes, mismatched stiffness , mismatched thermal coefficients, and inadequate manufacturing processes all add up to knock down your theoretical safety margins. I believe the joint failed it is the hardest part to engineer, second most likely hoop layers were micro buckled by subsequent hoop layers as they alternated between axial pre impregnated mushy high temp epoxy layers and room temperature gelling epoxy but not fully cured as layers were added. Autoclave final cure did nothing to consolidate layers just cured the epoxies.
@@JamieKunka yes but the axis is 0 degrees hoops are 90 degrees. This is done routinely when winding interface skirts for rocket motor cases. It is a problem on thick walled buildups keeping the laminate consolidated as you build up. Squeegeeing epoxy over the voids between tows is not a substitute for compaction.
@@JamieKunka Real information on the final manufacturing is sketchy, as different videos are shown as time passes. Either way if it was all prepreg that would be ridiculous to build up 5” of uncurled material.. I once had a carbon fiber flywheel project for U of Texas we had to build up and cure in stages to keep the fiber straight. We could not do it in one shot. Inter leaving prepreg and wet winding that thick is also problematic. A real tragedy and it will take a year for the NTSB to issue a final report.
I've been in composites for 30 years I've made helicopter parts blades nhra drag cars I agree the 4 in wound lay up was a mistake I also seen no mechanical adhesion sand roughing up of titanium nothing but I think the lay up was the big mistake it's weak that way especially under compression
wow those kink bands haven’t been mentioned in any analysis i’ve seen yet. good visual representation. i’d never heard of them. and THANK YOU for pointing out the technician cleaning that ring. it’s something that bothered me when i’d seen it before. i sometimes work on motors and i’m overly paranoid about the kind of towel/rag i’m using and how it’s affecting the mating surface of the parts/ gaskets. the rag he’s using doesn’t even appear to be residue free or microfiber in nature. i always hoped that clip of him washing the ring was for like press shoot lol
I think your probably right. I imagine he was made to do it for the video however. And even though he doesn’t appear to be touching the surface to be bonded, I think it’s still pretty shocking.
@@JamieKunka yeah right after i wrote that comment i noticed that he was rubbing down the OUTSIDE of the ring that would not be bonded with the carbon hull. still horrible practice. the environment in which they bonded the hull to the end caps was definitely concerning too. i definitely would be worried about foreign contamination.
@@JamieKunkai’d love to know how they transferred hydraulic lines or electrical components through the pressure chamber, stockton mentioned they have a manual handle that will release drop weights on the outside of the sub as a sort of back up system. how those connections got to the outside of the pressure vessel is interesting to me.
I've heard it said that it's all about surface preparation in mating dissimilar materials with adhesive - wondering if the initial failure mode was seawater working it's way into that titanium ring - carbon fiber hull connection. Will investigation be able to discern this?
The ductility of epoxy is reduced when the epoxy is dried from its wet state. Furthermore, to subject it after exposure to saline water, and then to the heat of the sun before the submersing of it again in saline water and then repeated heat will further reduce its effectiveness. Among the scientific studies: The Effects of Salt Water Aging on the Mechanical Properties of Epoxy Adhesives Compounds by Anna Rudawska (4 March, 4 April 2020). Other information abounds about this topic, not only to those who study chemistry and physics. Furthermore, simple research / education reveals that carbon fiber is an organic material; contrarily, titanium is inorganic with a highly reflective quality that does not corrode at all in prolonged exposure to the extreme pressure of deepest sea water, which of course includes salt, which aerospace vehicles are not exposed to. So many facts are available about the effects of epoxy on the two different materials. No visible traces of epoxy exist on the titanium rings that were recovered, which is to be expected of this inorganic material with its highly refractive index. The bond between the two different materials was sure to fail with prolonged exposure to the extreme pressure of saline water at ocean depths. Many of us who have worked with epoxy realize that the CEO and his associates ignore this obvious information that is publicly available.
It worked 11 times to Titanic on 30 other shallower missions. They were close. Didn't realize their margins were so small. 10% more plies and that thing might last for years and years. I'm still suspecting that bonded joint could be the root cause. We need to see the acoustic data from their hull monitoring system for all the previous dives. I'm not convinced that system would give them enough Time to ascend and get to safe depths. When composites finally let go, it's usually very quick.
I'm not sure 10% would make a great difference. The failure mode of rigid CF in a relatively malleable matrix, in compression, is surely quite different from that of homogenous materials subjected to cyclical tensile strain. I wouldn't expect the logarithmic gains you normally get from most materials, in most circumstances.
Hi Jamie, some excellent views, thank you. It would be obvious to me that because the hull had no end to end fibres, that when the centre of the cylinder deformed due to the pressure it would mean that the INSIDE wall of the hull becomes under extreme tension from end to end, this would then lead to a radial crack at the centre which then propogates through the hull to the outer wall.
I still haven't hear anyone explain how carbon fiber would be desirable to hold OUT pressure. It seems perfect for holding IN pressure as in an air tank but it seems (to me) that the crush resistance could only be a tiny fraction of its expansion resistance.
When I worked with a HYDROCLAVE our carbon fiber seemed to shrink and turn into a softer like graphite material! Unlike auto claves it could obtain pressures around 3,000 p. S. I . . Carbon takes on many different forms! OceonGate probably never considered using a HYDROClAVE because they are very expensive. They seemed to operate more like boat shop!
I've been watching a lot of videos about the Titan & thought the way you explained the process of the way the carbon & titanium were explained was excellent. Thank You 🙏
I’ve heard a few people say this. But I don’t think it’s correct. In Rush we have a man who hand-waved every rule and expert warning and ploughed ahead with a bad idea, seemingly implemented with a corner-cutting attitude. I see a lot of people grappling to understand this attitude, the level of hubris, the number of warnings etc. I see a lot of people incredibly saddened by the needless waste of live. And I see a lot of people dumbfounded that in todays age of safety and compliance and regulation this guy was able to build a test vehicle, avoid certification, and avoid any regulation. The above seems to be the overwhelming sentiment I’ve come across. But there has also been plenty of talk about how fast the implosion would have happened and the immense pressures involved and how scary it would be ti get locked into that thing.
Best video I've seen explaining the shortcomings of Stockton Rush's design and implementation. You did a great job explaining what are fairly complex procedures and the limitations of the design. Well done sir.
Isn't it crazy? Out of nowhere pop tens of thousands of deep diving submarine experts who know everything there is to know about building a deep diving submersible. They told us the submarine community was small. So small it was like a tight knit family. I beg to differ. I have come across at least 10,000 deep diving submarine experts on TH-cam alone. At least they all show up after the thing implodes to share their expertise. While the things being built, they're nowhere to be found.
The titanium ring should have been laminated into the body of the sub. In my industry making medical devices, we would NEVER trust merely epoxying in a titanium attatchment ring. It is always laminated in being part of the overall structure often with extra reinforcment. We often also use layers of different materials such as arimid, spectra, even fiberglass to take advantage of their benefits. Carbon fiber is super strong but it's also incredibly brittle and weak, especially at 90° to it's axis. Using muti directional layups doesn't have that much to do with torsion and more to do with alignment of the fibers so that the inherent weekness is mitigated...exactly the same as plywood. My theory though, is that the sub body was able to be squeezed more in the center which would actually make the ends go bellmouthed. With such a short flange only being held in by sketchy glue it would have popped like a cork.
I completely agree about the bell mouth ends I think this probably never happened in their simulations because of some dodgy FEA. I’ll probably make another video including the latest findings from the investigation.
Good video! For consideration, forgoing the predominant error regarding use of Carbon Fibre tow axially wound as a total misapplication of engineering principles, the geometry of the mating surfaces between the titanium ring and hull was completely misunderstood by Stockton-the-Princeton-engineer as well.
Jamie, this is so far the most factual analysis done about this accident. Most of the videos posted are mere opinions. You point out aspects that are not far from the cause of the accident.
Also what about the microscopic bubbles that are cured into the matrix as the epoxy cured? a pressure vessel that sees the extreme pressure that that hull did would compress and uncompress with each dive breaking strands of fiber with each cycle. He heard this crackling and yet he did nothing to address it.
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4:38 Hi, I’m a naval architect! “Strength-to-buoyancy ratio” is complete and utter nonsense. The buoyant force is only a function of the volume of displacement of the hull (provided that the hull isn’t flooded). A fully-immersed cylinder with a 2m outer diameter will have exactly the same buoyant whether it is made of carbon fiber or steel or titanium. If your requirement is a certain inner diameter, the extra thickness will get you some more buoyant force, but you could get the same extra buoyant force by simply making the metal hull larger to achieve the same outer diameter, with the added benefit of slightly more available volume inside the submersible.
TLDR: Archimedes is right and Stockton Rush is wrong.
Fantastic debunking! Thank you sir!
Thank you. I thought I was being dumb there when he came out with that one.
@@JamieKunkaGlad to help! It’s relatively rare that my expertise is relative to something in the news, but when it is, I’m more than happy to help elevate the public discourse.
@@michaelimbesi2314 that is true , the buoyancy is proportional to the volume regardless of what materials the hull is made of. but i think what rush was referring to is that he wanted to achieve a certain buoyancy with the lightest materials possible to reduce the weight of the sub.
He was obviously referring to how using a lightweight material like carbon fiber reduces the overall weight of the sub vs using titanium. It shouldn't be so hard to read between the lines. You're just twisting his words to make them sound as bad as possible really.
I have been an aviation maintenance technician for 32 years, specializing in aircraft structural repair. I spent 10 years in The Air Force, 5 working on the B-2 Bomber and had a lot of composite repair training. I am not an engineer, just a repair technician. Watching the video of the Titan’s construction made me cringe. To me, they did nothing right and everything wrong. Watching them “clean” the Ti ring and bond it to the carbon made me gasp out loud. We had a saying, “Cleanliness is next to bondliness”.
Since you’re here: So does anything about the Titan’s construction make sense for the aerospace industry? Because I’ve wondered if Stockton was taking what he apparently knew as an aerospace engineer and just assumed that a vehicle for underwater works the same way as planes.
I too was appalled at whàt I saw of the layup! I've worked on aircraft,, boats, roçkets, atomic submarines since 1957! Worked with autoclaves
And HYDROCLAVES. Also oñ filement winding machines. Yes, they were very naive iñ every respect, from the mixing of the àdesive to handling of materials! Did they use a vacuum chamber to remove the air from the adhesive? What was used to thicken the resin? Many questions!
Every step of this is wrong and that's only the tip of the iceberg. Absolutely stunned that it didn't implode on its maiden voyage.
Hi Chris, Retired USAF AFRL/ACO 2016 here. As a SME I applaud you for composite repair skills. I started the Mobile Training Team at the request of HI. In 2008 and personally trained over a hundred airmen in the field. In my opinion there were both design flaws and grossly inadequate manufacturing processes. This puts an unneeded smear on composite structures. The joint was the problem! Adhesives are great in shear not so good in tension terrible in peel strength. Some of the factors stressing the joint: dissimilar material stiffness, dissimilar material expansion due to temperature changes, hemispheres flatten out under pressure causing the bonding surface to dish out and put the joint in tension on the outer circumference. I was the principle manufacturing engineer on filament wound cases for the space shuttle boosters Air Force program to do a polar orbit. Canceled because of the Challenger disaster. In testing using water pressure the reverse loading condition of the submersible the joint was a big hurdle. At near 1000 psi the half dome hemisphere inflated like a balloon and the composite tube barely moved radially. This caused the Clevis joint on the dome to open up and expose the interior end of the pin to the pressure. The 2000 pounds of force on the end of the pin was like pulling the trigger on a gun. Pins were spit out like a machine gun as the joint failed in microseconds.
The AFT joint failed 6000 psi water pressure intruded compressing the air to less than a golf ball size and blowing out the forward porthole and the after shockwave blew the composite tube apart. Only epoxy in that direction no fibers along the axis.
@@oneskydog6768
I too am curious about the bond and see it as a definite contender for the leading cause of failure. In addition to the points you've made, I'd like to add a few thoughts of my own.
Having been in the composites industry for about 30 years, I have some experience with the processes and materials, although admittedly little with carbon fiber and zero with submersibles. I have been involved in design and manufacture of marine, wind blade, and infrastructure products. Much of my time was spent testing products, often to failure.
I can see multiple possible paths to failure in this vessel. It could be due to engineering decisions, manufacturing processes, material choices, quality control issues, etc. It could be a combination of two or more bad decisions. As an example of just one line of questioning, the carbon fiber hull was bonded to a titanium ring. Was the ring adequately designed for the bond? Was the bond compromised by flexing of the carbon hull? Inward flexing of the hull could act as a lever on the bond line. Bonding dissimilar materials can be difficult to accomplish. If the hull was stiff enough to withstand pressure and not flex, it wouldn't act as a lever causing a failure of the bond. If the ring was designed differently, could it have helped support the hull and thus, the bond of the hull and ring? We could surely come up with similar questions for each of the components of this vessel.
Most commentary on this tragedy leans towards speculation as fact. Watching a couple of videos where they show elements of the construction process doesn't turn us into experts on the structure and certainly doesn't make us qualified as failure analysis experts. I've commented on several videos where the overwhelming commentary is that the carbon hull failed, stated as fact. It's all speculation as nobody knows what actually failed. It could have been the carbon fiber, it could have been the bond interface between the carbon and the titanium rings. It could have been the viewport. It could have been something else. At this stage of the game, there is no one that "knows" what happened with any degree of certainty.
This is by far the best video I've seen on the topic. All of the points you make are right on, and there are a couple you didn't mention. I've 10 years experience related to the construction, testing and deployment of aluminum cylindrical pressure vessels rated for full ocean depth, and 6+ years winding thick carbon fiber cylinders. Regarding implosion testing, the weakest side of the aluminum cylinder begins to buckle, putting the interior surface of the aluminum under tension, and any resulting fracture begins there. Carbon fiber cylinders are strong under tension, that is, high pressure from the inside surface, but there is no lengthwise compression strength with carbon fiber. More to the point, when under extreme internal pressure, the carbon fiber cylinder actually grows physically in the radial direction. If under external pressure as with the Titan, the strength in the radial direction is unknown to me, but if the composite is pressed inward by the uniformly-exerted pressure, it is likely to shrink slightly. If this rate of dimensional change is even slightly different than the titanium end rings, this would produce shear forces at the glue joint during a dive. Each dive could stress and weaken the glue joint more and more. The only way I know to effectively bond titanium to carbon fiber is by a difficult process that involves more than just glue, and was not mentioned. Lastly, for carbon fiber with a high number of layers, as shown, many things, especially the fact that the epoxy shrinks while curing, often results in voids and tangential cracks internal to the cylinder which cannot be seen, but are revealed when a test section is cut from the cylinder and inspected. My supervisor has told me that metals expand with temperature, while carbon fiber shrinks with temperature. I don't know if that's true, but if it is, it would also be a problem. Thank you for your excellent video.
With all the new data coming out, your comment seems to have the most insight. Though from what i can understand the data points to delamination of the carbon fiber layers putting excessive force on the titanium end rings, specifically the inside wall of the Ti-CF overlap, causing them to shear off.
6:17
Rush handing him the glue on a tray, while he's on the topmost step of a random stepladder is really a metaphor for the whole operation.
Mixing the Pipi Longstocking super Gluer with a stick😂😂😂😂😂😂😂😂😂😂
Cutting corners..
He approached other companies to build it but they turned him down (because they knew it was a terrible concept) so he got a bunch of plumbers to make a glorified PVC pipe... money doesn't buy intelligence.
Wow I am very surprised that he even managed to make it down to the Titanic with that construction. Extrodinary ! 😮
One positive from this incident is the case study it gives to all future engineering students. Universities should come up with courses covering all the engineering concepts behind this failure.
I hope this incident gets dissected and every little lesson we can get out of it is learned. I hope that this tragedy is not wasted.
Yep, Oceangate University.
-Don't do this 101.
-Not like that 202.
-No frigging way 301.
The engineer behind the Hyatt Regency Walkway collapse in KC spent the rest of his life lecturing on the mistakes he made that lead up to the disaster.
They probably already knew this would happen.
They cover all the base concepts needed in the first semester at any engineering school.
No BS. No sensationalism. Solid content.
Thank you for sharing your experience on these materials.
Even myself, a layperson with 0 years working with composite fibres and 2-part epoxy-style adhesives, was staring with disbelief as they slid the two pieces together, by hand, IN AN OPEN WAREHOUSE AND IN STREET CLOTHES.
*I've seen woodworkers do more prep work before applying layers of topcoat to a piece of furniture* - wearing full-body suits in a sealed environment, and so on. And no one's life is on the line if the finish being applied to the furniture you're working on has a bad spot or three.
A bad spot or three on a deep-sea submersible, on the other hand, means instant death. Quite literally.
Just unbelievable. You can't pretend you know what you're doing when building something like this. LIVES ARE ON THE LINE, YOU DAMN WELL BETTER BE SEXTUPLE-CHECKING EVERY TINY DETAIL AND ASKING EVERY EXPERT YOU CAN GET YOUR HANDS ON TO OFFER THEIR BEST TIPS.
Firing everyone who told him "no" and hiring nothing but kids fresh out of college (who could be browbeaten or intimidated into never telling him "no") probably didn't help much, either. Why hire industry experts? Those guys are *EXPENSIVE* and will tell you "no" to your face. College grads, on the other hand, tend to work for a fraction of the salary and tell you what you want to hear, 'cause you're the CEO!
The hubris on display throughout this whole sad saga borders on insanity, like Stockton truly believed that the Universe would bend to his whims, that all his "innovative engineering" was infallible, and that he could defy the laws of physics through sheer grit and determination (while saving a bunch of money in the process).
You hit the nail on the head there, hubris and ego above lives and proper engineering practices. A very sad saga indeed.
@@JamieKunka
I am also a layperson but with an extensive background in a range of technical disciplines . GLUES RESINS AND EPOXIES HAVE CAUSED MANY DEATHS if not mixed properly ...BOSTON MA .. BIG DITCH TUNNEL PANEL DROP is a typical example ..it killed the occupants of a minivan when it dropped because the EPOXY used to anchor the suspension bolts ran like molasses in JULY.
Besides the obvious being addressed by the expert analyst ...RUSH was too full of own self generating BS , he believed in his own BS as most legends of one`s own mind do enough so as not to listen to anyone, but his own misguided mind.
The engineer and those workers have blood on their hands now. Did any of them ride down in the Titan death trap at anytime I wonder? Who was the inspector working on this submersible, he or they too have blood on their hands. So did SR but he died in the implosion but I'm not sad that he went down with his flimsy submersible. PH should have known better and sounded the alarm, but would SR have listened to him?
@@MissX905 Stockton seemed to take anyone questioning his "innovation" as a personal attack, so I seriously doubt it.
What's even worse is the shop that made this "vessel" and glued it the way they did. Granted they probably did it based on the spec provided but I work in that industry and when we see shit that is an obvious no no we say something. The shop that made the shit is liable in a way as much as ocean gate in this instance. But that's my opinion
Rush's workshop is little better than mine (I am a musical instrument maker working at home). I take greater care in gluing and bonding than these guys do. Amazing. I will give him some credit: he went down with the ship.
so Rush got ripped off from the sounds of it
Rush may not even deserve much credit for "going down with...". OceanGate's former finance director said that Stockton Rush asked her to be the head pilot for the Titan after the former pilot, David Lochridge, previously said he was fired for noting concerns about the sub's safety. She quit because of that.... or maybe she had limited experience with Game Controllers?
Rush seemed eager to keep the money coming in and appearances up. Would it be too much to speculate if the finance director knew other valuable information that was best left buried at the bottom of an Ocean?
Yes, I heard had they used titanium and steel for the body instead of carbon composite even with other problem, they could have averted the implosion.
@@kamilebrahimoff3589 could have but didn't
if you think about it, it was kinda like watching a turdlog do the disco circle before disappearing down the black morass
It should have been double prooffed. Meaning that if they were going to be operating at 6,000 feet, it should have been built for and tested at 12,000 ft.
That would require a crazy level of over-engineering.
correct it should’ve been common sense to have a Margin ,, if you’re towing a 7000 pound trailer, get a truck with a 9000 pound towing capacity, not a 7000 pound towing capacity.. I mean, this is nearly common sense in the engineering world, it’s astonishing. He was pushing it at the limit.
@@andychow5509100% more than expected is incredibly reasonable when human lives are concerned.
You're soo off I'm guessing your completely uneducated in the topic and just throwing numbers out that sound good. Most submersibles do 120% their operating depth, your talking about 200%. Titan didn't even have the extra 20% either, and since the carbon fiber tore on the very first dive it definitely wasn't even rated for Titanic's depths let alone had a safety margin.
@@sertank735 that's what an uneducated person would say, since industry standards are 120% and there's never been a problem till now. Titan didn't have that safety margin, it wasn't built right to handle the depths it was going to, the carbon fiber tore on the first dive, and yet you think its gonna somehow do double its operating depth? Geez, your so ignorant about submersibles idk why your even acting like you know what should be done and what is a good level of safety. 120% is actually more than enough, but your sub has to not only be built right but be able to handle 100% of it's operating depth without it falling apart every dive. Carbon fiber isn't a good submersible material period, nor should we take this accident and try to change industry standards when this sub had nothing to do with industry standards, and actually went so far off industry standards it imploded. The problem started at the design phase not at depth, the sub was just so bad it couldn't even operate 20-40% it's operating depth without the carbon fibers tearing. Every other submersible does 120% and has never had a single problem operating at 100%, because they didn't use carbon fiber and their design was actually good and safe. Just get educated if you wanna act like you know what your talking about, because clearly you don't.
Doomed from the get go ... no Clean Room, no Auto-Clave and no AS9102 certification to keep it all on the straight and narrow. But hey, that's just what my 40 years in Aerospace Composite Engineering tells me. Just imagine if Rush had invested in a "Thread laying machine" (TOWS) like we use on our F-35 Program ... much stronger ... and Rush wouldn't have been able to buy that expired (and obviously "re-tested" once) CF Tape from Boeing !
And THAT folks is why we call it "HALT" ... highly accelerated lifetime testing ... "bend it until it breaks" so you have a baseline. IMHO, the Hull imploded and had NOTHING to do with the Titanium flanges/dome; the acrylic view port and domes blew off like Champagne corks (Water cannot be compressed and it had to go somewhere) ... studs smooth as a shiny new whistle ~ zero threads left nor CF tear away on the mounting flanges (there are ZERO “Adhesives” on the professional/FMS market that don’t call for application of a “Primer” prior to the actual Adhesive). His "Design Engineers" sucked ... the hull was in "hoop" yet zero internal stringer supports nor sleeve to help keep it equalized; hull thickness would have needed to be approximately 17.6 inches thick without said support structure. All the "popping noise" on previous dives was the CF delaminating, transitioning from "Elastic" to "Plastic" state ... the fibers ripped out of the resin matrix bed and never able to re-seat; Rush would have known this had he bothered to perform NDI (ultrasonic or X-Ray) after each dive. Pity his hubris got in the way. Good presentation Jamie.
Agree. Rush fired his design engineer after he raised safety issues. Rush was a narcissicist. When I listen to Rush speak he is an obvious noob.
Yes, you’d think ultrasonic testing would have revealed the defects before the vessel was submerged. And also the ruptures that developed under pressure.
@@maxenielsen yes, it would have identified the delamination areas ... "X-Ray" for more accurate locations ... but he was such a cheapskate he skipped it.
I've worked as a NDT-technician in the windturbine business, and i'm apalled that the CF hull never went through any testings for airvoids or delaminations.
A suicide waiting to happen, but there was no need to bring more.
BSME here. Carbon fiber has incredible strength in tension, not compression. In compression the strength is almost entirely that of the adhesive, not of the carbon. Foolish design, foolish testing methods, foolish egos.
I've been wondering about the titanium/carbon fibre interface as well. The bonding procedure taking place in an open industrial workshop and not in a cleanroom. The lack of proper safety equipment; scaffolds etc. No one suited up for clean operations, no vacuum chamber to pull air from the glue joint. The mixing of the glue in an open environment. It all seems quite amateur and hasty.
When I saw the clips of the assembly, I was thinking "Surely they had a vacuum chamber somewhere. Why didn't they mention it?". I don't know that much about epoxy, but I know that anyone doing serious work with it has to find a way to get rid of the inevitable air bubbles as part of the cure schedule. That work looked like me patching the hull of my sailboat.
Or my attempts at fiberglass objects!
True, the biggest problem of all was the carbon composite, which could not handle the water pressure at that depth, so it imploded.
There was like 40 megapascals of force pushing that titanium cap against the carbon fiber. That adhesive was just gap filling once that thing started down. The issue isn't going to be some dust, it is going to be whether the interface at the edges can mechanically tolerate the cycles.
@@kamilebrahimoff3589the thing is - it did handle that depth, but it could not repeatedly handle that depth. The egomaniacal fool at the wheel (Stockton) confused the two as well.
im a former professional glass fibre pipe system builder (power plants etc, 7-8years) and I absolutely agree with the issues you point out. TBH it looked that they had very little clue about what they were doing and was just winging it, hoping for the best. Also I think the different thermal expansion coefficient of the materials used could play a role.
"Didn't see any glue squeeze out" I design loudspeakers and I would have fired the vendor for this - for a loudspeaker. Absolutely insane.
You would think that thing would be assembled in an airtight chamber and then put in an autoclave
That’s a fundamental tenet for applying adhesives. I’ve done everything from speaker reconing to carpentry. Insane.
@@thecloneguyz ..by workers wearing PSA, with a prezise construction frame to hold all parts in place by µm, measured and leveled with lasers. Direct control of the joint with Xray scanners after leaving the autoclave and and and...
I don’t think it’s an actual glue. It’s more like a filler putty as the pressure holds the body together no glue is needed that’s the way I see it especially as the fiber shrinks with compression. If it were a set bond type glue it definitely would crack and not adhere. I think of it more as a playdough type material that never cures . But what do I know it’s just a mindset. They had external collars that wrapped around to secure and seal at shallow depths as the depth increases the pressure holds everything secure. Until the hill starts cracking over and over of your expired super cheap deal carbon fiber. It was actually expired so he got it at a discount
“Don’t just stand there , get some glue!!
Anyone?
I am a naval architect and marine engineer. I spent over 33 years working for major oil companies. All of my work was in design, engineering, maintenance, environmental issues, and spill response. I spent a considerable amount of time working on fatigue cracking particularly in critical areas where cracking could result in catastrophic failures. I have no experience with carbon fiber. I did at one point own a fiberglass sailboat.
When I first heard the reports of the missing submersible and heard that it was a carbon fiber cylinder with titanium end caps, I told my wife that there was no hope of rescue. When the videos of the hull construction started to be shown, I told her that the design was flawed and was destined to fail.
I agree with your comments on using a single radial wrap was a critical error. There should have been a weave pattern to strengthen the cylinder to handle the axial compression from the end caps. Even my sailboat's hull was laid up with crossing wraps of fiberglass. The Titan was subjected to multiple dives where the carbon fiber tube was subject to fatigue from the compression and relaxing of the axial load of diving and resurfacing.
The arrangement of the rings and the bells leaves much to be desired. Securing the rings to the carbon fiber with glue alone, with no mechanical backup raises questions. The use of 18 bolts to secure the bells seems to be odd since a pipe flange at 6000 psi requires 44 bolts. I heard in several reports that the hatch end bell only used 17 bolts because of difficulty in tightening the 18th bolt.
The lack of Classification Societies' input was a fatal flaw. Let's assume that review and approval have a zero-time and zero dollars impact. Skipping Classification meant there was no third-party review of the design, there was no fatigue analysis, there were no failure modes and effects analysis, there were no inspections and certifications of components during construction, and there were no in-service inspections.
I told my wife if I had a disposable income sufficient to waste $250,000 to visit the Titanic to look out a porthole, please excuse the expression, "I wouldn't be caught dead on the Titan."
The man was an amateur, how did he get in charge of all this... the vessel at the absolute minimum should have been tested to 8k psi double the normal if I were in charge.. and I'm amateur..
When you say "pipe flange at 6000 psi" I assume you mean 6000 psi on the internal surface of the pipe? That's quite a different load on the bolts to 6000 psi of external pressure like the sub would experience.
The radial wrap was likely found to be a necessity to avoid density voids. The fibers were two directional in the tape: 90-0. They made a previous hull and it made lots of noises. This was their second hull and it was a lot better. Don't underestimate the effort they put in this... I myself thought; why not make an inner tube in metal to connect the ends, but then I realized any leakage would pry the two materials apart... What they were doing was far from easy...
The force on the endcap bond is closer to 28000 psi. ( the full surface area of the end cap applied to the surface of the carbon fiber tube) Critical epoxy mixtures are mixed by weight, not volume.
Air was certainly trapped in the ring when the joint was made, not enough pressure to squeeze out the air bubbles. Also, an autoclave bond is required for high strength composite layups. I am surprised this sub lasted more than one dive.
Very interesting to hear your calculations on the pressure. I’m uncertain if any pressure was applied to the interface cap when it was bonded or do you think they were just relying on the weight of the machined part pressing down on the hill?
@@JamieKunka From looking at the sloppy ness of the bond, I do not think they applied extra weight at assembly
@@JamieKunka The surface area of the Carbon fiber tube is approx 1300 in sq. 5 psi of bonding pressure needs 6,500 lbs of weight.
@@glennnovember3266 Using rough numbers for the dimensions I got similar results: -139MPa (-20ksi) for longitudinal stress. What is interesting is how they must have thought they had a margin of safety with the 0/90 layup since the resin alone was probably rated at -250MPa. I am also curious of the hygrothermal stresses of curing a 5" thick wall. This guy was definitely way off of charted territory on this design..
Rush built this craft with inadequate funding. A bunch of guys building something in their garage. Sad.
The mating of the titanium to the Carbon Fibre is something I've had thoughts on. Years back I used to install strain gauges in the aviation industry - mostly aluminium alloys and titanium, but also on carbon fibre. The process for metal and CF involved using different solvents to degrease the parts, and keying the surface was also a little different. The process I was taught required titanium to be warmed with infrared lamps to drive out surface and subsurface contamination like oil, during which solvents were used until the surface was clean, and various fine grade oxide papers were used to sand the surface in figure eight motion to key the surface to bonding the gauge to...which then had a light acid applied and neutralised...the process with CF was similar, but less intensive, without heat lamps. The main difference was the type of glue applied for bonding. We used a special proprietary bonding agent manufactured by strain gauge manufacturer. The CF used a different bonding agent based on a cyanoacrylate type glue.
My understanding back then was that the same glue/bonding agent could not be used for titanium and CF, so was surprised to see a glue being used to mate both surfaces. Also surprised the surfaces didn't seem to be keyed - especially the titanium - ready to receive the glue!
Another concern was how shallow the join was!
I've always called the deliberate roughening of a surface to be bonded giving it "tooth" - similar to how the term is used to describe how paper will hold graphite from a pencil when drawing.
Absent that increased surface area, and scrupulous cleanliness, you have almost zero chance of forming any effective bond to a metal surface - and, the adhesive which you choose to apply must be to some degree corrosive to the metal in order to achieve a chemical bond.
Further, you join needs to ave significant resistance to slippage, much like mating screw threads have a force resistance projecting perpendicular to the direction of tear-out.
And, these slip-joints had absolutely nothing in the way of resisting elements to hold against tear-out forces.
Just a bad job, physically and chemically, even before you look at the actually assembly "procedure"...
I dont know anything about these materials how do u bond carbon fibre to titanium (if not with glue)
Great to hear the interesting details from your real world bonding experience. This just goes to show the length and precision we must go to do make such bonds.
Meh why not just get 4 guys in t-shirts to slap some bondo on it, squeeze it together, and call it a day?
@@inthefade :D
Absolutely insane the carbon was only applied this way, anyone who ever 3D printed a tube knows that it breaks in the layers, this is no different, actually impressive it survived as many dives as it did.
I pictured the water pressure like an ax trying to chop a piece of wood, and how much easier it is to chop with the grain than against it. Also, since the fibers were all in the same orientation, a few layers buckling could cascade through the entire carbon fiber hull. I think the strength of the carbon fiber hull would easily have protected against implosion at least several times better if it had each layer going in a different orientation than the layer before it.
Aside from that, I didn't like the fact the carbon fiber hull can't be bolted into. I would never trust diving under water in something bonded together by nothing but glue. When I first saw them gluing it together, my first thought was a massive "Why?!" It was kind of like witnessing an idiot in a horror film about to get themselves killed.
To be fair, Rush clearly states the fiber orientation is 0/90 (1:33 mark), meaning equal amount of fibers in the axial direction and the hoop direction. Still I agree that some +/- 45 degrees also would have made the hull stronger. Rush justified not having +/-45 by saying that there are no torsional moment, which is technically true. Problem is, this is only true as long as the hull is completely intact. As soon as there is a little damage to the hull. The +/- 45 degree fibers would have helped redistributing the loads around the defect. I am a structural engineer with carbon fiber experience.
@@davidosterberg how would they run a axial layer with a setup like that? Wouldn't the turned ends of the mandrel prevent them? I guess they removed the ends or there would have be axial layers at the top only???
@@AORD72 That is an excellent question, that I don't know the answer to.
@@AORD72look up ElectroImpact AFP. That's how the built that hull.
The footage of the wreckage overlayed with Stockton Rush talking about his sub is some dark humour right from the depths of hell and I am here for it.
Recent graduate in Naval Architecture & Marine engineering here - take everything I have to say with a grain of salt because again, just graduated and by far not an expert!
But my 2 cents on the "strength to buoyancy" term you mentioned. My first reaction is this is the first time I've ever heard this term utilized, I also have not spent much time with submersibles as they are definitely a niche in the industry. However my next reaction is that term seems a tad bit silly since the buoyant force must be equivalent to the weight of the object (Archimedes Principle), thus in reality strength to buoyancy is practically the same thing as saying strength to weight. Strength to weight is also not really a metric used all too often in Navarc, when designing commercial ships (think tankers, container ships, dry bulk etc) weight is certainly a concern from a cost and strength perspective, but it's often not the case that in commercial design you compare the strength to weight ratios of various materials, it's just not as much of a concern since the body of water will just displace more volume to account for a heavier ship - and often these commercial ships are volume limited. In other words, commercial ships often reach maximum capacity of their cargo holds long before they're in any dangerous territory of displacing too much water.
Weight becomes much more a concern when talking about high performance yachts such as the Americas Cup sailing vessels. But the usage of composites in these craft is vastly different that in a submersible... The question that still troubles me is that someone must have realized that Carbon Fiber does not have the same strength in compression that it does in tension? I wonder if the strength to buoyancy ratio he was using accounted for the different compressive strength of carbon fiber, since pressure vessels under seas have to deal with compressive loading (greater ambient pressure) while airplanes often deal with tensile loading (lower ambient pressure).
Thanks for the comment and information and great to hear from a Navarch graduate!
I just found your video, excellent job, my first alarm bell was the way the CF was wound one layer on top of the last with no overlap or weave pattern, you don’t need to be an engineer to see all the flaws of this design
I’ve taken a submarine design course (and used Paramarine for a project) and never heard of “strength-to-buoyancy ratio”. There is a factor called “weight limited designs” which the structure material plays into; it’s why HY80 has been superseded by HY100 and HY130 in newer classes of US subs: these are stronger materials and can thus be thinner and therefore less weight to the hull. But buoyancy has a lot of other factors not just the hull material.
On the titanium cleaning clip, good catch! But based on where the rigging is laid out, it’s unclear if this would be the bonding surface or just the external surface. Either way, the controls in the entire process are COMPLETELY negligent at BEST.
No glue squeezing out of the end caps when they laid it up definitely threw a red flag for me too the first time i saw that video. Very good analysis vid 👍
Same with me, I have no idea about this technology, but seeing they place the end cap on top of the carbon fibre and no glue coming out made me nervous
I try for some glue squeeze-out with woodworking projects, but I’m also fond of using screws In addition to glue.
*lots* of screws.
@@dennisyoung4631 - you should have built that submarine of course
@@dennisyoung4631 I'm work in a cabinet shop and another thing I notice was that they didn't even have to tap it in place it just slid right down on it
@@Blasko86 got a question for you, then.
When I am putting pieces of 1/2” nominal birch plywood in slots/grooves/Rabbets/?, I commonly try for a “drop-in” fit, one where there’s (hopefully!) no needing to bang things with a mallet. (I’m working alone, still relatively new to woodworking, and am older, chronically ill, *and* disabled. Most of the shelving units, bookcases, etc. are more *disability accommodations* than conventional furniture.)
I use hide glue, because it has a long open time, is relatively easy to clean up, and doesn’t leave visible stains under the finish. I then put in #6 countersunk screws.
Am I full of for doing it that way? Unlike metalworking, I haven’t done it for a living, nor did I take college-level machining classes. I did my share of reading, and I have asked people about it who have more experience than I do.
I hear Rush patented his “real time hull health monitor” system. He also said in previous dives the cracking was loud and persistent. Since we know that cracking sound was the sound of a hull progressively weakening, his monitoring system was obviously another useless idea.
the loud cracking sounds was cleverly fixed by asking passengers to listen to music
@@DelphiAmnestieddamn I didn't see that way. That's insidious of him
No, not useless. Just useless in the context that it was employed in.
The more time that passes the more I hate that guy. This is all his fault.
I’ve have no expertise in these things but it seems like cracking sounds equals damage. Damage that can’t be properly repaired or even evaluated. To continue to use something you know is damaged for a mission that dangerous is insane.
▪ _"A former OceanGate finance director said Stockton Rush asked her to be the head pilot for the Titan."_
▪ _"She told The New Yorker_ (Magazine) _that she quit when the OceanGate CEO urged her to replace the former pilot."_
▪ _"The pilot, David Lochridge, previously said he was fired for noting concerns about the sub's safety."_
"Fine I'll do it myself".
Pretty scummy. I hope they get sued and are forced to file for bankruptcy
@@221b-l3tStockton had that M. Bison energy fr
Reading this after Antonella and Lockridge's court hearings shows that we all knew what lead to this when it happened. Now, all we are doing is trying to reconstruct the implosion to see when it happened, at what depth, and if the passengers knew it was coming.
Ironically, a Pringles can is actually better engineered than the titan sub was.
Because a Pringle’s can was engineered.
And like a Pringles can... once the Titan popped; it just couldn't be stopped...
Titan was just a giant Tylenol.
Ironically, a third grader running on little sleep could compose a better grammatically-sensible sentence
@@theseatownfunkpodcast1332Ironically, even a third grader can see how childish it is to make a jab at a random innocent person's grammar for no reason.
I think the problem was the difference in stiffness between the carbon fiber and the titanium end caps. Under the pressure¸ the CF cylinder would have compressed in the radial direction much more than the titanium ring. This would lead to radial shear and bending stresses in the glue joint.
Exactly what I was thinking.
There were just so many pathways to failure, about half a dozen that seemed inevitable. Various things to go wrong in the bond, same in the layup. Rush really had a psychological blind spot in his intolerance for criticism.
As a materials engineer, the difference in modulus of elasticity between the titanium and composite seems like a likely cause of failure here. Computer modeling was likely used to calculate the stresses involved, but there can be many reasons for adhesive bonds to not meet the properties listed by the manufacturer. Consequently, extensive testing of the bond should have been done before risking human life in the vessel.
I was thinking this too. Seems like you would want the more elastic material on the outside so pressure increases the bond rather than pulling it apart when it's inside the titanium.
This is a definite possibility, and is what my first thought was on hearing that the sub had titanium end caps and a carbon fiber pressure hull.
Kudos for the slide discussing the necessity for surface preparation of the titanium for adhesive bonding - that's better detail than I've seen in any of the other discussion to date.
I'm skeptical about the emphasis on the glue, although it is certainly indicative of an overall sloppy attitude to quality control (and health and safety). The external pressure will tend to push the end caps harder onto the carbon fibre tube the deeper the dive, closing any voids without putting any sheer load on the glue. Since the pressure increases progressively during the dive any water leaks through the glue interface should have been apparent before they became dangerous. The carbon fibre tube may well have compressed more than the titanium ring, but the latter seems to have an internal channel the inside edge of which would have broken off if this were the root cause of the failure. My money is still on a simple and entirely predictable fatigue failure of the carbon fibre tube.
John,
That’s the way I see it too. Extreme compressive cycles on a material designed for strength in tensile loads.
The hoop stress means this carbon tube is gonna shrink in diameter. If the titanium shrinks at a different rate, massive shear stress. Temperature changes can result in insane shear stress.
I did a simulation on a pool window of poor design: 300,000 lbs due to thermal stress alone
@@ZebraLemur However, as I said in the OP, it is not a simple butt joint. The carbon tube is glued into a channel in the titanium ring. Under the strain you describe, the inner lip of this channel would be stressed and would have to break off for there to be significant movement of the glue joint. The titanium parts seem to be completely undamaged in the images we have seen. Conceivable that localised damage was deliberately or accidentally hidden as the parts were lifted ashore, but it will still be known to the investigators and should resolve the matter one way or the other. The fact that the carbon tube has not been recovered, or even significant intact pieces of it, also argues for this as the original failure.
Yeah but you're not thinking about the fact that the carbon-fibre compresses at a different rate than the titanium and what would that do to the mating surfaces?
@@thecloneguyz mating surface - nothing good. Just saw another video on this sub where a professor from Europe runs modeling software on this vessel under pressure. That model of the failure looked like the Pringles can being squeezed, everything was over in just a handful of milliseconds. The highest stress was at the Ti-CF joint. After the joint failed and the cylinder shattered the two titanium end caps were driven inward at high speed and ‘clapped together’ in the center where the cylinder used to be.
After seeing this I have now come around to seeing the Ti-CF joint as the biggest problem. No matter what the adhesive or procedure used, this joint is the location of the highest concentration of stresses. Since there were several successful dives to this depth before this incident, material fatigue cycles must have played a role. Perhaps the glue joint finally failed, or the carbon fiber itself became weaker and deflected more on this dive, or both, or something else (he also identified the acrylic window as a weak point). The titanium hemispheres that were recovered looked brand new from the brief unloading video.
If there’s one silver lining we get out of this, it’s that hopefully many composites professors and industry SME will use this as a warning to future engineering students. Similar to how Tacoma Narrows Bridge is well-known and taught in the engineering community.
Actually there is already a lot of research and examples, in fact it's on every label of composite adhesive products
@@scifi_shop There's research and there's stories like this one that are good examples to convey that research at each step of the way.
Don't hold your breath. It isn't like engineers didn't already know ALL of this before the sub imploded. Some of them even tried to warn them. Still, they did it anyway and killed 5 people.
@@stargazer7644 We all do because we have experience. I'm talking about professors teaching new engineering students. I see how my OG comment didn't make that clear. Edited.
It's a big event people know of that they can use as a starting point to a set of lectures.
I don't think this is really comparable with Tacoma Narrows. Tacoma Narrows was, as I understand it, a bridge that failed because we didn't know you need to consider XYZ when building a bridge (specifically, the possibility of aerodynamic flutter causing resonance). Its failure taught us lessons that could be incorporated in future suspension bridge design. Titan's failure seems to have been caused by ignoring things that we already understand well. There's no lesson to be learned, because we already knew not to do all that stuff.
Unless your point is that now there's a practical demonstration of what happens if you ignore these things.
For generations to come, videos like these will train future engineers how NOT to design a submersible.
Good job Sir, in training us laymen on complex engineering subjects.
MOST if not all (in that small community) already KNOW and knew this submersible’s design was a tragic accident (time bomb) waiting to happened
I hadn't thought about that! This wreck is the 'How NOT to build a submersible' like the Forestall (or 'Forestfire' as my naval friend says), is the standard video on how NOT to fight an aircraft carrier fire.
Unfortunately these findings are nothing new, similar things have repeated in the history over and over again. What we learned from this: RTFM with materials&glues etc and let certification people do their work and go through everything or work with them to establish best practices to ensure safety.
@@timop6340 🤡 statement
@@nadagabri5783yes, I'm wondering if someone could of sent a lawyer or a letter to Everett Washington explaining the dangers and get the occupational license revoked so they couldn't operate. This could of caused unwanted press coverage for oceangate and exposed them before a tragedy could occur..
Even as a layman, my jaw literally dropped when I paused the video at 6:45. It's like me helping my dad do a DIY project around the house.
YES!!!! thats exactly what I thought ,like here ya go dad ill hold it up for ya then we've finished up we'll have beer whadda say hey ...bloody madness
It's horrible. No hair nets, no face masks. I seriously doubt the glue was homogeneous at all. And they didn't even degas the glue. Seriously, with the cost of epoxy, I take more care doing a small project than these guys.
It's clear they didn't care. The guy with the dirty rag... It's titanium, right? I'd assume you would wash the area with some solvent so it's absolutely debris free. I'd want to be in a Hepa filtered room, but if that wasn't possible, I'd wear a hair net.
When you put a semi-liquid surface, there's a tool that tells you the actual depth of the stuff (usually paint, but works with glue). In other words, people painting industrial surfaces take more care than these guys did building a prototype submarine. But they seem to be mixing it glue by hand in tiny flimsy containers.
Excellent video. However, the biggest problem is that carbon fiber has a much lower modulus of elasticity than Ti. The tube wanted to shrink by 1/2" at depth, but the Ti wouldn't let it, resulting in an ENORMOUS stress concentration on the inside of the tube at the junction of the Ti, resulting in buckling.
...or the adhesive bond failed prematurely.
Just shocked that this was glued together. I'm surprised it sustained one dive without popping.
It's now 9 months later and I still find myself digging for more quality Titan content. I have no relation to the sea, diving or engineering and have zero understanding of why I'm STILL fascinated with every angle of this event.
Really good content btw! A+
Thanks and hope it was interesting!
Im the same im a 57 year old woman who is into poetry and music and yet I find the whole thing fascinating.Stockton was magical in his need for ego accolades ,if he wasn't he would have done everything with expert care and precision
"Squeezing a can of Pringles" Exactly the analogy I've been using to explain to friends that the Titanium rings overlap with the CFRP was way too short.
Yes - but a longer overlap poorly bonded would probably still failed. But agree - so short!! And the 90/0 fibre winding - insane!!
I don't agree completely with that analogy, because it implies the initial failure had to be radial. However, don't forget that in the sub, there is also an extreme amount of pressure on the end caps pushing in, thus reducing the need for much ring-tube overlap, and I suspect the initial failure was the tube itself in axial direction, not radial. And the reason for that, is the 1:3 scale model Oceangate tested to failure. You can see a picture of it at 3:46 The tube is still round, it's the end that is pushed in, delaminated/shattered and has separated from the metal end rings and caps (not in the picture). So a better analogy could possible be that you take a Pringles can and stand or jump on the lid so the tube buckles/shatters, and not the other way around. And if that was the cause, it would probably not have made any difference if the ring-tube overlap was ten times longer.
@@Kowalski301 do you know how they tested the 1/3 model? Cycle testing or just loaded up until failure?
@@AORD72 We have to assume they did some cycling before full pressure to collect more data, especially since they made a big deal about the so called "real time monitoring" system that would detect abnormal movements and acoustics in the hull, that would change from one dive to the next dive, and that the scale model had fitted some of these sensors, but I can't say that for certain. Stockton only talk about the scale model test very briefly and doesn't specify it any more other than they took it to failure and the shockwave blew out all the pressure sensors in the chamber. They did the tests at the University of Washington so there should have been at least some smart people in the area...
@@acebacker1 Love all you instant engineers.
It’s stunning this deathtrap made it more than one dive.
Well I guess he had 5 inches to play with. Cracked through 1/2 inch per dive? Holy fluck
@@steveo601good point
So fascinating. It’s very uncomfortable watching how DYI this build was! 😮
Not a fascinating as all the INSTANT Marine engineers that appeared.
@@blackhd92 right? incredible stuff
It feels like Stockton was just guessing. Had some interesting ideas, implemented them haphazardly, cutting corners, didn't test them in any way, ignored warnings, and just YOLOd it. It wouldn't have been so bad if he was just risking his own life, but he also convinced 4 others and took them down with him.
People are allowed to think before going with him. He wasn’t forcing anyone. Like getting in a fast car with someone who says it will all be fine but there’s always a risk. And even someone without knowledge in engineering could see this was made to fail
@@PT-mj3bktrue. Problem is he probably didn’t properly convey the actual risks. When I went skydiving, I also had to sign a bunch of waivers and consent forms. The company still had a responsibility to provide a safe experience - if the instructors were inexperienced, planes and equipment poorly maintained, corners were cut, etc., I would have had no idea. I simply knew their track record was good (no deaths in over a decade) and trusted the company. Oceangate depended on these paying customers and Rush made all sorts of misleading claims about the safety of the vehicle and went out of his way to convince clients (e.g flying to meet with them) - it’s impossible as a customer to accurately assess the risk if the company is dishonest.
@@sue8412 Yes, and to add to that, Stockton claimed they collaborated with NASA, Boeing, and U Washington, but that was a lie. Stockton was also warned by his own employee as well as external experts about his fault design, but he ignored them.
@@PT-mj3bk A better fast car parallel would be if the driver failed to tell you the car was improperly maintained and that it had had some issues on previous rides that were brushed aside. Also, the car is not actually road safe, but the driver failed to mention it. Also, in case of a crash, the airbags may or may not deploy, but the driver also forgot to mention this and other details that are necessary to make a fully informed decision.
You can not tell a Narcissist anything, they will do the opposite.
A quick search and we find that the 'circumferential' stresses are double that of axial stresses in a 'thin walled cylinder'. But I've also found that so-called 'transverse' strength of carbon fiber is a lot less than when applying along the length of the fiber. So even if there are no 'torsional' stresses, certainly there are axial loads, and being applied perpendicular to the fibers. That seems to be a BIG problem (IMHO).
It’s a miracle it survived the dives it did
Hearing all those people criticize his design must have been crushing. He probably didn't appreciate all the pressure.
Are you tacking a crack at what would have been a smashing success if not for the depths of ignorance involved?
@@DoublePlus-Ungood I say this with the deepest sincerity. I mean it from the bottom of my heart.
There is more cleanliness and care taken in boat fiberglass work and auto body painting than what is shown in Titan construction.
Right? Painting a car: every surface is prepped and meticulously wiped down to get rid of every spec of dust. Paint is sprayed on in a paint booth that has an air filtration system by techs in full body suits. And then there's ocean gate mixing up batches of glue by hand and applying it the same way in what looks like a dirty industrial facility.
Richard Stockton Rush had poor eyesight - he was also blind to Titan’s fatal safety limitations.
Even if there weren't any air bubbles entrained in the adhesive during mixing and application, there would be microscopic gas bubbles formed by the leaving groups coming off of the monomers as they polymerized to form the join.
Normal procedures to remove these bubbles include curing at elevated temperature under vacuum in order to draw the gases out of the adhesive.
My experience in the chemical industry is with using Fiberglass Reinforced Plastic piping and tanks. The glass fibers give strength to the composite when in tension. For a cylinder, tension of the shell occurs when the pressure is on the inside (pushing outward, i.e. attempting to deform the cylinder into a larger diameter). The glass fibers resist this tensile force by not stretching, like a rope wrapped tightly around a pipe. When the pressure is on the outside of the cylinder, the composite is under compression, which the fiber reinforcement really does not help with. Here, the structural strength is provided by the resin, a thermoset resin, i.e. a cross linked totally rigid non-plastic material. It does not yield like a metal under load, but rather cracks microscopically each pressure cycle until the structure fails all at once.
I agree that the end glue joints to the titanium were riddled with problems. The biggest problem that leaps out to me is that the whole cylinder relies on resin for its strength, resin being a type of glue itself !!
I am interested to hear from folks who have experience with both carbon fiber and fiberglass in compressive loads. Is the fiber reinforcing principle the same or does carbon fiber have additional properties that would help it in compressive loads?
if the composite had been formed with 3-d cf, it might have survived - worked well, even. But principally 1-d circumferential, eh?? The wall stress within the cylindrical hull main body would also not have been in pure radial compression, the end-caps would be applying (very approximately) 1/2 the radial stress, but in the z-direction - i.e. along the long axis of the cylinder; the cylinder was therefore in triaxial stress - was this accomodated?
@@jesflynn4048 thanks for the insight. I’ll have to look up 3D carbon fiber, sounds like exotic aerospace. The loading on the end caps you mention is another compression load, perpendicular to the CF fiber winding direction. In this direction the fiber provides no reinforcement strength at all, just filler. I looked up the deep sea expedition by Victor V. His submersible is named something “Factor”. He did it right: designed and built by an experienced submarine company, pressure vessel 100% titanium, and they actually pressure tested it to 120% of max depth. It worked great.
I've worked with carbon fiber and fiberglass! They are totally different critters! My experience that glass doesn't compress, but carbon changes character when compressed at different pressures and heat! Where do you think diamonds come from? I've worked with HYDROCLAVES working at 3,000 P,S,I, our carbon "cloth" turned into graphite! It works great for boats or aircraft.!
This was a really thorough, informed and thoughtful analysis of the various problems with the design and manufacturing of the submersible.
I'm not an Engineer, rather I'm a physicist, and some of these issues seem disappointingly trivial, even to someone with my lack of relevant knowledge and experience.
Not correctly texturing the surface of the carbon composite and/or the titanium dome before bonding the two...
From Year 7 D&T I can remember being told to rough up surfaces a little before gluing things together, give the glue something to grab on to.
I saw all these things in the video, it was surprising so few people picked up on the cleaning of the titanium rings for instance, I put signs together and if I saw one of my staff touching the surface before the VHB tape was bonded with bare hands I’d be very upset and tell him how to do it properly and that’s just with street signs!. I don’t want them coming off the posts in a high wind and killing someone. These people didn’t even seem to understand this most basic concept. Again, as you saw, no glue coming out of the join when pushed together = no glue on the join. Also try sticking two perfectly flat surfaces together with glue, can’t be done properly can it, there will always be massive air bubbles. Go on, get two sheets of glass, hand spatula glue all over both sides, offer them up to each other almost completely flat and you know what you will see when you hold them up = Massive air pockets, not just bubbles but air pockets!. How could this person call themselves an engineer? What stupid exams did he pass to get his qualifications without the slightest understanding of how materials work. I’m just a sign manufacturer and I get it. Also at the most basic level I understand the difference between compressive strength and tensile strength. Not one of their engineers did. The only thing holding that thing up under that pressure was the strength of the resin, not the strength of the carbon fiber because carbon fiber is “only” strong when stretched, not bent or compressed.
Hi, I'm an engineer who has worked on Racing and custom Bike applications, using carbon Fibre parts. I had many reservations about using or making carbon fibre parts, after watching many catastrophic failures during the early years with mainly wheels being the parts. They would suddenly disintegrate on track, after looking perfect in the pits, just before they left, not hard as they were all practically new items. All the parts required bonding to Metal machined parts usually aluminum or Titanium, which would then be Bolted up, using either steel or Titanium studs or bolts to attach the other parts. It was found that Carbon Fibre had Die-electric properties of its own, and as a result acted as a dissimilar metal if Bonded directly to the Metal part using carbon fibre parts, after a couple of uses for let's say a front wheel with an aluminum hub, which was then bolted to steel front disc rotors, would advanced corrosion that could be seen upon disassembly, and the same could be seen where cracks or separation had occurred at the carbon to metal interface. This was remedied by coating the boned metal part in normal fibreglass resin and then applying the carbon fibre layup to that while still tacky, or when dry machining a course surface into it. Now true the forces we are looking at are completely different from the mostly compressive force you are considering, but after seeing the same video you showed in your explanation when this occurred, it didn't surprise me at all to see the interface come up completely clean and free of any distortion. To be honest, that was exactly what I expected to see actually, if the Boned surface had held at all, with the way it was constructed I would have expected to see at least some stands or parts of strands still dangling to it. I expect, and would suggest that at least a few of those cracks or bangs were at least in part, the carbon-to-metal interface separating until when "Loaded" with 5 people on board it finally separated completely and cleanly, leaving the hemispherical bell at each end as manufactured, not deformed? I expect it was the forces from the implosion that blew out the observation window. I'm really sorry for the other people on board, who were conned into going down in this thing, the whole thing was a sad Joke! Continuous monitored settling cracks? even this supposed "safety system" was a Farce what exactly is acoustic measuring going to do for you, other than annoy you just before or while dying. What this so-called Engineer, did is tragic, and the very reason we are professionals with demonstrated safety factors in place for a reason. I've worked for two Major companies on pressure vessels, with pressure, being both positive and in a Deep vacuum. I've also been nearly killed and was finally seriously injured, due to a like employer. Despite a multitude of written warnings and a year-long refusal to work further on this project, regarding safety limits concerning how the initial load was applied, rather than a gradual build-up as designed, it had become an instantaneous shock load, and it failed exactly as predicted throwing a 500lb endbox thru the air over the Machine and Control panel were I was standing and it struck me on the shoulder. This kind of Engineer gets us all a Bad name? and his victims Killed and injured.
Thanks for your great comment and insights into bonding metal and carbon. Great to hear some real world industry experience. Very sorry to hear about your gung ho employer. I fear there are far too many folks out there like that pushing the envelope too hard, too fast. Fine if your putting yourself at risk as the only end user but not when it’s other people’s lives. Hope your shoulder has recovered well!
@@JamieKunka Thank you very much, for your nice comment.
Sorry for your injuries! I reminded me of a similar situation that I was in! - working with composites. I was lucky and escaped the explosion, just in time! I warned my fellow workers, who at the time thought that I was crazy! We all eventually escaped without harm,, when they saw I was serious,! To many engineers think because they got a better education, they are above reproach and are superior minded!
@@robertchilders8698 Yes, watched it Happen as the engineering profession was revamped, as their goal is more prestige and the ability for connected Burracrats who just happen to be in Engineering rush to get seats where they'll never have to be an Engineer again, just administrators. I could write a book about the cock-ups and Deaths these idiots have caused, during my career, being that I've worked at most levels. I had to go Find a friend's corpse once, that had been left to stew in the cooling Tower pond over the weekend, due to the layout of the plant, and the Machines being up on a catwalk, over the pond. He was carrying out a yearly inspection, I'd been there with him on Friday when he placed all his Lockout padlocks on our Breakers. Meanwhile, some cocky Maintenance Engineer had decided to use an extra set of contacts going spare on this Machine to Bring on a pump, he never thought about this situation. He needed the pump for process, so it could run with the other Machines we had 6 there. So He ordered someone to cut off the Lockout padlocks and turn the power on while they temporarily got another feed to the pump, He Killed our Guy a Family man with 3 young kids, to his death, to save face for an extra 5 minutes. He stated that he had told someone to go tell our guy, But it never happened and as my Help wasn't needed again till later, I was sent to another emergency as it was summertime on a Friday afternoon. Honestly, I have enough to fill a Book, including my own. This is one of many examples of this, where the project was completed without the Machines ever leaving the loading Dock or even the street in one case, Cop's Coliseum, Do you Know How many people must have come and gone and said something to him about Missing Machines? Once in London, the plant room was at the lowest level of the underground parking, The Building was like a Lifesaver shape, a Hollow circle, They had to smash open all that rebarred concrete and then we Dropped the Machines in through the Top, $500,000 a pop for the machines then all the services to hook them up, electrics, plumbing, welding. Instrumentation, pumps sensors, Microprocessors enabling the building control, All there, doing nothing, I'm only supposed to be there at the end to inspect all that work and or troubleshoot if theirs a problem, and remedy it, regardless. and turn everything on making sure it reaches Design parameters, How does someone who is supposed to be a fellow engineer, walk past the Machines every morning and not clue in ? It's amazing and these are the Guys rushing out of Universities, who have never seen a bloody thing until they get a Job, and then they are suddenly managerial Material, My old Boss was ex-Navy when I was going through my Qualifications and Training, He would have punched your lights out, then depending on circumstances he'd have decided if he was keeping you on or not. In those days getting let go, mid-training or just after was the Kiss of Death, yet I know many of these never even got a reprimand. On the Sub, it shows this Kind of thought, who else would design a WARNING system for about to die or dead? Regards Ian
Worked for an adhesive manufacturer. With adhesive, less is more. Firstly, there would ideally be a primer applied for the adhesive to 'key' onto.
The bond line needs to be thin and consistent to get the best surface/surface to contact. Applying by hand with what looks like a tile spreader isn't going to be very constant, and will lead to an uneven bond-line, introducing weakness in the adhesive bond. Should be applied by robot to get consistency and the correct bead (similar process to a car windscreen).
Excellent point about fibre orientation. Single direction creates perfect path for cracks progression. I guess this is the key design flaw. Picture in 2:45 is showing perfectly what probably happened.... 👍
It also strikes me the carbon strands at the ends of the tube will be irregular where the machine laying it on the tube former changes direction (eg at 2:16). There would have to be some bunching of the carbon fibres on the inside of the bend formed as the head changes direction because of the width of the tape. There would also be some inconsistency as to where these bends lie on top of each other, just where there are the loads transferring the axial compressive forces from the titanium ends onto the tube. I guess the idea was that the resin glue would spread the load, but it does look to be an area where repeated loadings would lead to settlement and cracking.
Very interesting hypothesis, I also believe the interface joints failed causing catastrophic compression. The two dissimilar materials definitely pose a very high risk of separation at the pressures experienced at that depth. I've seen pressure tanks for SCUBA made of carbon fiber, which are lighter than their metal counterparts, but are limited in their number of pressure cycles. It will indeed be interesting to see how future test and experimentation allow carbon fiber to be used in future under sea exploration. Very well done video on your part.
Bonding area is pretty important and a tapered sleeve on outside with 3-4 x the overlap would have possibly preserved the bond. However he mentions not seeing any bonding agent squeeze out....When we bond and pot things with thickened epoxy a real problem is when you slip one thing over another or inside another, you scrape the glue off the sides and push it into the end which also traps air. The ends aren't even touching 100% . You go back later for a repair and cut through to inspect and that is what we see.
1 year later and your analysis confirmed to be spot on - congratulations
Most deep sea vehicles are made as a sphere whereas the Titan was a cylinder but I have not read much about the difference of how a cylinder would act under extreme pressure compared to a sphere, the shape of the Titan may be part of the problem as well as the materials and construction methods.
7:00 An extremely good point I haven't heard anyone make yet, any air in-between those mating parts would have collapsed to nothing possibly breaking that seal in sections and putting undue stress on the carbon fibre parts and possibly introducing torsional stress as one section of the hull flexes more than the opposite side.
If they used any kind of micro balloons to thicken the resin, it would contain small amounts of air that could be compressed Rescue bueys on atomic submarines were made with phenolic micro balloons that were good to down about 3,000 feet!??
5:39 I noticed the guy touching the parts after wiping it with a dirty rag too and 9:30 no glue squeezing out, I almost had a heart attack when I saw them gluing them together. No thank you, No way!!!! You're crazy i wouldn't go 10 meters in that thing !! And to think they thought it was good to go bring on the paying customers.
Extremely interesting including the comments, with people of different areas of expert knowledge contributing. Shows one reason why we have specs, so that the knowledge of different areas can be collected and applied. And why him refusing to be certified was such a folly.
Not only the compression properties ( as opposed to expansion rates ) of the three components, but more importantly the distortion. The carbon fiber hull will begin to distort into an oval, whereas the titanium ring will distort out of true, the bonding between the two will have to “stretch”. This certainly explains the “cracking” sounds heard. That is the point of failure, allowing high pressure water (6000psi) to infiltrate the joint and act as a hydraulic wedge instantaneously pushing the two surfaces apart. Failure is highly predictable and catastrophic. Working as a senior structural engineer for Lockheed Martin within the Marine Division, this very phenomenon has been studied and documented repeatably. It s disturbing that any research Oceangate did, they either didn’t access the available data or discounted it.
Note: The guy wiping the ring down with a shop rag appears to be removing stray dust from the opposite side of the parts from the actual bonding groove. This is also a necessary step, as stray dust can migrate as the part gets craned up and over the CF cylender... hoever, he's not wearing a "bunny suit" and thus can leave skin cells and hairs behind after wiping down.
Not a good situation on the non-bonding surface, but definitely a poor practice indeed on any surface where you want to achieve a bond.
Totally agree with you ...
I bet he’s feeling pretty shitty. Yeah, wipe with cloth with one hand and then rub over it with his other bare hand. Yikes!
In a cylinder, pressure (internal or external), will be two times in the hoop direction (circle around the cylinder) but one in the axis direction. For rockets and internal pressure you either add end to end loops or use a 27 degree “magic wrap angle” which provides needed end to end strength without giving too much hoop stress.
I heard that there were layers of multiaxial carbon fabric added by hand in between the zero degree uniaxial wrap. But haven’t seen documentation.
Very interesting about that magic angle. I do wonder if a design more like an internal pressure vessel, would have done much better over time. Will be interesting to find out if any other axis were used…
I'm not an engineer. I'm just your average layman. When I watched a video of a guy hand spreading the epoxy resin to bond the carbon fibre pressure vessel to the Titanium end cap in what looked like an open-air hangar facility, I was incredulous. It struck me as amateur and didn't make sense, especially given the depth that the submersible would be diving to. I imagined that the interface between the two materials would be really important and therefore would be treated as such and not undertaken in such a casual manner.
You've pointed out some of the questions I had about the carbon fiber section. The two part epoxy applied with a mixing nozzle, reorienting the fiber direction in subsequent layers, and proper surface prep should have been no-brainers. I have yet to hear anything about how the carbon fiber section was cured. Aircraft industry standards for curing composites is to bag the part (on the mandrel) and apply a vacuum inside the bag to compress the layers before and during oven curing.
Overall, it seems either shortcuts were knowingly taken, or someone didn't know what they were doing. But what do I know...I'm just a 68 year old white guy that worked in manufacturing laminated aircraft components (including heat forged carbon fiber airframe connectors).
Finally, a well documented, balanced video that doesn’t just go “carbon fibre is bad in compression, that’s sooo obvious, these guys are dumb, brrr”. I’ve recently watched video from real engineering and was a bit disappointed in that regard. But your vid point exactly to realistic potential sources of failure. Well done!
I’m so glad someone brought up the ‘carbon is bad in compression’ trope, I feel it’s thrown around a lot without. Whilst it’s true it’s only 30-50 % of its tensile strength with proper fibre alignment one can mitigate the disadvantages a fair bit!
This is the best video I've seen so far because you are looking at specifics, not just criticizing Rush for a lack of concern about safety. My guess is they just didn't have the budget for a proper job, whatever that might be.
Thanks for your professional input on the matter. My cousin, who professionally fixes yachts, said a similar thing, just with fewer details and with a lot of swearing. I use home made carbon/kevlar composites only for fixing RC toys. Before I touched the stuff I watched about 40 minutes of tutorials on Easy Composites website and without the slightest exaggeration I'm way more qualified to fabricate composite parts than any of those Ocean Gate engineers.
Sad but mostly true !
You'd think a deep sea sub with novel hull material ought to be legally obliged to go through the necessary tests and certifications.
If not in international waters, they would be. That's how they got around the certification.
I’m okay with people taking their own dumb risks for exploration or sport. We don’t make wing suit athletes certify their wings. But OceanGate better have been very very thorough and honest with every design detail in their marketing etc before they had those people sign wavers.
If you’re up front and honest about the risks, I think people should have the right to do stupid things like this to an extent.
I feel bad for the kid though. What an irresponsible father.
If it carried passengers it must be ":classed". hence, they were crew, supernumery.
Exactly, an agency should have done a final inspection to clear it for the dive.
It didn’t have to because the submersible only operated in international waters and was carried through territorial waters as cargo on the deck of a ship. By operating only on the high seas and not being registered in any country, it was literally outside the law. Rush deliberately chose to operate it only in international waters because doing so meant that he was literally outside the jurisdiction of any country.
I have 28 years experience in the middle east as technical manager in composites, and agree with you that the bond between cf and titanium was a question mark. For me, i will never introduce different materials for this application and compensate with a huge value for manufacturing constant not less than 10, and a value of 3 for cyclic load constant..Also, i agree with you, he should have placed layers of helix winding. Filament wound should be one-piece such as this kind of application.
It's just astounding how many mistakes and corners were cut by this guy. Strength to Bouyancy is horse-quaqamole. Buoyancy isn't what kills you at 12,000 ft, its pressure. I'm amazed this thing actually held together for 10 other trips. Mr Rush was truly a "baffle them with bullshit" and "smoke and mirrors" engineer. Its shocking and sad people paid good money and risked their lives with him. Informative video!
1:38 Rush says the ply orientation is at 0/90 which covers the axial and circumferential stress (2X axial). It’s not a single fiber orientation which is repeatedly mentioned by the narrator. I’d also be curious what the preload on the end rings during bonding. The adhesive isn’t under the usual tensile and shear stress either since the structure is under compression and the adhesive stress is mainly due to poissons stress. The lack of excess adhesive is less critical for this type of joint stress.
Excellent informative video without sensationalism. Thanks
I think that this is the best analysis of the OceanGate sub. And the only one that I've seen that's placed any attention on the bonding and process and the fact that the titanium ring was recovered with not a bit of fiber on it.
When you hear the guy talking about and wondering, and almost bragging about just 'How far out the box' he is operating, it makes you feel sick that he could do this AND take others with him AND charge them a quarter million dollars at the same time. He will be remembered as one of the worlds biggest Wankers
Great to see some knowledgeable, objective discussion - thanks.
Hadn't heard Rush saying "no torsional forces" but as someone who has spent a lot of time in small composite boats in tidal waters, this doesn't ring quite true to me.
If you consider a dive in a swimming pool, the predominant force is indeed the compressive water pressure. However, the ocean is a much more dynamic environment. From tidal streams near surface, to the deep ocean currents moving vast distances, a diving sub may potentially cross many interfaces where the water on either side is moving in different directions.
In addition, they towed the sub on its raft out to the dive site. The raft will have protected it from the stresses of bridging between wave crests, but depending on weather it may have been subjected to irregular wave impacts.
I don't know the relative magnitude of these forces, but I doubt they should be written off as negligible. Even if each instance is not overwhelming, surely they would have a cumulative effect?
Willing to be corrected if wrong!
(Re layup: even our small carbon fibre boats are vac-bagged!)
The carbon fiber and titanium have different compression strength and behavior. While they seem snug during the construction, at depth there would be a small but significant difference in the diameter of the fiber cylinder and titanium ring which would put a lot of force on that little layer of epoxy. I’m surprised it lasted as many dives as it did.
I am an electric / electronic engineer, who worked for decades as a commissioning engineer for high-tech vacuum coating machines, installing and repairing them on all continents.
1. When I saw the toy play station controller, it was clear, they also skipped any industrial (not to mention submarine) standards. Electric / electronic components within a ship should have at least a certain degree of dust- and most importantly water-tightness. If there is some slight leak within the ship, water might just start to drip onto these components. But water should never be allowed to come in to keep things controllable, even if it is just for the emergency routines. It is also important to avoid internal fires and electrocution of humans.
Our factory-based = land-based industrial machines have watertightness requirements (like higher IP-categories) when electric / electronic devices (sensors, valves, etc.) are to be assembled i.e. in or near water-cooling circuitry for the very same reason.
2. When I saw all the spaghetti-style power- and control lines (electric, air etc?) on top of this wacky "submarine" without any mechanical protection against whatever might come along, I knew these "engineers" are just charlatans. How can you keep control lines of any kind in a rough environment like the deep-sea so exposed? There might be so many unthinkable objects or perhaps large fish / whales bounce against it or get entangles there, i.e. while cruising around a huge rusty ship wreck or being lifted in and out of the waters.
It is amazing to see such extreme thoughtless botch from thousands of km/mi away through shaky TV-cameras.
The BS-phrase of "thinking-out-of-the-box" became obviously a complete new meaning or "level"; I personally rather stick to my profession and keep thinking inside the box - for safety's sake of the people operating "my" machinery.
Just by looking at this "submarine" (before it imploded), I would never have put my butt into it. Any old lawn mower feels more safe.
Peace! from Dresden / Germany
CRP is still a sort of mystery material today. I've been in aviation manufacturing and we don't know exactly what it's hysterysis/longevity really is. And that's after 40 years.
I spent 30 years in the composite business. I have filament wound structural members. In glass and epoxy resin. We used two types windings Circ's which was similar to what he used. But we used a winding called Helix on every other layer. And the band end to end with like one revolution. That entire layer was like basket weaved for a complete layer. Then another layer of Circ's to pull everything together. The Carbon to resin ratio is also important to dry and things pull apart, to wet and it becomes brittle. Bonding the titanium end caps didn't bother me as much as the winding pattern did. Just my opinion.
Intuitively, carbon fibre going only one direction seems like a terrible terrible idea. I realise the primary strength will be going around, but that leaves no room for error if any part is weakened a bit.
Without fibres thing the other way, the point where the titanium ends and the fibres have to stand alone would be under enormous stress.
The primary strength will be going around IN TENSION. Carbon fibers are like wet noodles, they have no strength in compression. The only strength here is in the compressive strength of the resin.
@@stargazer7644 wrong, they're not like a "wet noodle", the compressive strength can be up to 50% of their tensile strength. Also, the epoxy holding them together has great compressive strength.
@@xpusostomos Carbon fibers are THREAD. You can hang your car from a single 1/4 inch carbon fiber rope in tension with well over a 2 times safety margin. So you're telling me you can balance that same car upside down on the end of that same 1/4 inch rope in compression? Have you ever actually handled carbon fiber fabric? Carbon fiber alone has almost no compression strength. In a composite the resin is just about the ONLY strength carbon fiber has in compression. Using carbon fiber to make submarine hulls is like using concrete to make tubes for pressure tanks.
@@stargazer7644 There is much you don't understand. Firstly, the sub wasn't made of carbon fibre cloth, but strands of fibre, all going the one direction. Secondly, to make a tube lose structural integrity by pressing on it the inside of the tube would be under tension while the outside would be under compression. Thirdly, the compressive strength is measured when the fibres are in alignment with the force applied. In a rope under tension, they are kept in alignment by the tension. Under compression you've got a problem keeping those fibres perpendicular to the force. But the sub is not a rope trying to hold up a car. Fouthly, carbon fibre has about 4x the compressive strength of steel. So let's say you wanted to support a car with some material by compression. What's a good material? Most people would say steel, that's what every car lift is made of. That's what every set of car ramps is made of. And yet carbon fibre is 4x better. Fifthly, don't listen to me, use Google and find out for yourself.
Saw this I think on Reddit. One reason SpaceX switched from carbon fiber to stainless steel pressure vessels (fuel tanks) was the difficulty of detecting structural flaws. I'm a lay person but my father is an architect and builder of skyscrapers who also went to Princeton only years before Stockton Rush. The federal regulations and codes in the construction industry, especially high rises, are insane but are very necessary. I'm sure the "crackling sounds" they heard was that carbon fiber breaking up! What else? Or those seals coming loose or that damn Plexiglas porthole that was inches too thin. Stockton was always talking about people in the deep sea exploration community using a "safety argument to disrupt innovation." The problem is you can't argue with time tested engineering and physics. If you're going to use carbon fiber, it must be in a woven pattern, not a single weave. That isn't strong enough. And that video of those guys applying the glue? Why weren't they using an autoclave? Wearing gloves? It's insane. That thing was built by students who had no idea what they were doing, lead by an arrogant greedy man who skimped on materials and had no regard for anyone else's safety pr lives, not even his own. It's all very sad.
Very good analysis of what and why likely happened the Titan implosion. Thanks.
IMHO it's even intuitive that the carbon fiber layers should be put ALWAYS in several (many, even some layers at random?) different angles to get all its properties, strength and to diminish the advance of delamination and its speed of propagation.
The RTM that Stockton included into his carbon fiber submersible was a good idea (indeed as per the transcript, it took about 19 minutes since the moment when the RTM alerted something was wrong with the carbon fiber hull to the moment of the implosion). So, if just he would have laminated the layers at many different angles, likely he had time enough to save the situation.
Also, it's pretty clear that the delamination was already quite advanced since the beginning of that last dive because it descended faster than predicted (and yet faster as the submersible was diving deeper) and it then did ascend very, very slowly despite all their efforts, which was "unclear why rate is small" (I guess due to the delamination the carbon fiber hull was being compressed, deformed and so bending slightly and more towards the mid section of the tube, firstly silently, then loud enough for the RTM to note it and, finally, with terrifying bangs and cracking sounds...). As the hull starts to give in to the pressure and bends inwards, it displaces less water, hence it loses buoyancy.
The carbon fiber composite is very hard and light material... but fragile when its limit is exceeded. So for submersibles, even being well constructed with carbon fiber, I think it's better to rely on other materials which are able to deform without cracking, like high quality stainless steel.
And also the shape it's very important. Needless to say that the sphere is the best shape for this task. But, the shape of a rugby ball it's better than a cylinder shape (because the arc shaped structures are much more robust than the straight lines) as it's so widely used in construction of dam retaining walls and in architecture.
Being in carbon fiber since 30 years for racing purpose, when i saw how they just wound the carbon on that tube without making a cross wound that allows resistance of both axis i was flabergasted. At the two tube ends the resulting pressure from the two caps are is applied only on the tube end surface in a direction that the wounded carbon fiber give no resistance. So in this way only the matrix resin can hold the pressure and will cause a quick wear and of course the bounding is also a problem. But you have to keep in mind that the glue doesn't hold the caps, the water pressure press so hard that without any glue in would hold. Just look at how the two caps are bound to the two titan rings, just a few little bolts to keep it toghether.
The problem is that the carbon made the way they did it gives no resistance in the tube axis and then nothing keep the wounds together except the resin, this is nuts!!
Nice to hear from someone with experience in carbon fiber composites. (CFCs) - titanium construction. A couple of questions come to my (4 year mech eng degree) mind.
(1) water will seep into any tiny pore or crack due to capillary action. What is known about water at 5500-6000 psi forcing its way into tiny cracks of the resin matrix & promoting delamination or such? Or would the compressive stress tend to close the cracks? Maybe no one knows the answer since most deep sub manufacturers want nothing to do with composites in their pressure hulls.
(2) I noticed what looked like a step in the circular edge of the CFC cylinder, that is, a reduction in diameter from the main wall down to where the Titanium end caps/rings are glued on. To my mech eng mind this screams out “possible stress concentration” which is double deadly under cyclic load. Are CFC subject to stress concentration due to changes in section (or notches) to the same extent as metals? The edge may be designed with a proper radius (or not) I can’t tell watching on a tablet.
Look up a report from last year, "review of composite hulls in deep water"... they even were kind enough to include pictures.
Physics does not care what material it is concerning stress concentrators , section changes, material changes, mismatched stiffness , mismatched thermal coefficients, and inadequate manufacturing processes all add up to knock down your theoretical safety margins. I believe the joint failed it is the hardest part to engineer, second most likely hoop layers were micro buckled by subsequent hoop layers as they alternated between axial pre impregnated mushy high temp epoxy layers and room temperature gelling epoxy but not fully cured as layers were added. Autoclave final cure did nothing to consolidate layers just cured the epoxies.
Are you aware of them hand laying layers of 90 over their 0 degree pre preg filament wind?
@@JamieKunka yes but the axis is 0 degrees hoops are 90 degrees. This is done routinely when winding interface skirts for rocket motor cases. It is a problem on thick walled buildups keeping the laminate consolidated as you build up. Squeegeeing epoxy over the voids between tows is not a substitute for compaction.
@@JamieKunka Real information on the final manufacturing is sketchy, as different videos are shown as time passes. Either way if it was all prepreg that would be ridiculous to build up 5” of uncurled material.. I once had a carbon fiber flywheel project for U of Texas we had to build up and cure in stages to keep the fiber straight. We could not do it in one shot. Inter leaving prepreg and wet winding that thick is also problematic. A real tragedy and it will take a year for the NTSB to issue a final report.
I've been in composites for 30 years I've made helicopter parts blades nhra drag cars I agree the 4 in wound lay up was a mistake I also seen no mechanical adhesion sand roughing up of titanium nothing but I think the lay up was the big mistake it's weak that way especially under compression
wow those kink bands haven’t been mentioned in any analysis i’ve seen yet. good visual representation. i’d never heard of them. and THANK YOU for pointing out the technician cleaning that ring. it’s something that bothered me when i’d seen it before. i sometimes work on motors and i’m overly paranoid about the kind of towel/rag i’m using and how it’s affecting the mating surface of the parts/ gaskets. the rag he’s using doesn’t even appear to be residue free or microfiber in nature. i always hoped that clip of him washing the ring was for like press shoot lol
I think your probably right. I imagine he was made to do it for the video however. And even though he doesn’t appear to be touching the surface to be bonded, I think it’s still pretty shocking.
@@JamieKunka yeah right after i wrote that comment i noticed that he was rubbing down the OUTSIDE of the ring that would not be bonded with the carbon hull. still horrible practice. the environment in which they bonded the hull to the end caps was definitely concerning too. i definitely would be worried about foreign contamination.
It’s possible he might have done the same to the bonding surface off camera! We just didn’t see that bit.
@@JamieKunkai’d love to know how they transferred hydraulic lines or electrical components through the pressure chamber, stockton mentioned they have a manual handle that will release drop weights on the outside of the sub as a sort of back up system. how those connections got to the outside of the pressure vessel is interesting to me.
I've heard it said that it's all about surface preparation in mating dissimilar materials with adhesive - wondering if the initial failure mode was seawater working it's way into that titanium ring - carbon fiber hull connection. Will investigation be able to discern this?
The ductility of epoxy is reduced when the epoxy is dried from its wet state. Furthermore, to subject it after exposure to saline water, and then to the heat of the sun before the submersing of it again in saline water and then repeated heat will further reduce its effectiveness. Among the scientific studies: The Effects of Salt Water Aging on the Mechanical Properties of Epoxy Adhesives Compounds by Anna Rudawska (4 March, 4 April 2020). Other information abounds about this topic, not only to those who study chemistry and physics.
Furthermore, simple research / education reveals that carbon fiber is an organic material; contrarily, titanium is inorganic with a highly reflective quality that does not corrode at all in prolonged exposure to the extreme pressure of deepest sea water, which of course includes salt, which aerospace vehicles are not exposed to. So many facts are available about the effects of epoxy on the two different materials. No visible traces of epoxy exist on the titanium rings that were recovered, which is to be expected of this inorganic material with its highly refractive index. The bond between the two different materials was sure to fail with prolonged exposure to the extreme pressure of saline water at ocean depths. Many of us who have worked with epoxy realize that the CEO and his associates ignore this obvious information that is publicly available.
It worked 11 times to Titanic on 30 other shallower missions. They were close. Didn't realize their margins were so small. 10% more plies and that thing might last for years and years. I'm still suspecting that bonded joint could be the root cause. We need to see the acoustic data from their hull monitoring system for all the previous dives. I'm not convinced that system would give them enough Time to ascend and get to safe depths. When composites finally let go, it's usually very quick.
I'm not sure 10% would make a great difference. The failure mode of rigid CF in a relatively malleable matrix, in compression, is surely quite different from that of homogenous materials subjected to cyclical tensile strain. I wouldn't expect the logarithmic gains you normally get from most materials, in most circumstances.
Easily the best video on this I’ve seen, and one of the few that didn’t just regurgitate the same info we already know.
I'm an engineer Jamie. EXCELLENT, use of your expert analysis. Thank you.
Hi Jamie, some excellent views, thank you. It would be obvious to me that because the hull had no end to end fibres, that when the centre of the cylinder deformed due to the pressure it would mean that the INSIDE wall of the hull becomes under extreme tension from end to end, this would then lead to a radial crack at the centre which then propogates through the hull to the outer wall.
Precisely! This is absolutely what I think happened as well.
I still haven't hear anyone explain how carbon fiber would be desirable to hold OUT pressure. It seems perfect for holding IN pressure as in an air tank but it seems (to me) that the crush resistance could only be a tiny fraction of its expansion resistance.
When I worked with a HYDROCLAVE our carbon fiber seemed to shrink and turn into a softer like graphite material! Unlike auto claves it could obtain pressures around 3,000 p. S. I . . Carbon takes on many different forms! OceonGate probably never considered using a HYDROClAVE because they are very expensive. They seemed to operate more like boat shop!
I've been watching a lot of videos about the Titan & thought the way you explained the process of the way the carbon & titanium were explained was excellent. Thank You 🙏
The whole world is on a morbid curiosity kick with this sub.🙂
I’ve heard a few people say this. But I don’t think it’s correct. In Rush we have a man who hand-waved every rule and expert warning and ploughed ahead with a bad idea, seemingly implemented with a corner-cutting attitude. I see a lot of people grappling to understand this attitude, the level of hubris, the number of warnings etc. I see a lot of people incredibly saddened by the needless waste of live. And I see a lot of people dumbfounded that in todays age of safety and compliance and regulation this guy was able to build a test vehicle, avoid certification, and avoid any regulation.
The above seems to be the overwhelming sentiment I’ve come across. But there has also been plenty of talk about how fast the implosion would have happened and the immense pressures involved and how scary it would be ti get locked into that thing.
Best video I've seen explaining the shortcomings of Stockton Rush's design and implementation. You did a great job explaining what are fairly complex procedures and the limitations of the design. Well done sir.
Thanks very much!
Isn't it crazy? Out of nowhere pop tens of thousands of deep diving submarine experts who know everything there is to know about building a deep diving submersible. They told us the submarine community was small. So small it was like a tight knit family. I beg to differ. I have come across at least 10,000 deep diving submarine experts on TH-cam alone. At least they all show up after the thing implodes to share their expertise. While the things being built, they're nowhere to be found.
The titanium ring should have been laminated into the body of the sub. In my industry making medical devices, we would NEVER trust merely epoxying in a titanium attatchment ring. It is always laminated in being part of the overall structure often with extra reinforcment. We often also use layers of different materials such as arimid, spectra, even fiberglass to take advantage of their benefits. Carbon fiber is super strong but it's also incredibly brittle and weak, especially at 90° to it's axis. Using muti directional layups doesn't have that much to do with torsion and more to do with alignment of the fibers so that the inherent weekness is mitigated...exactly the same as plywood. My theory though, is that the sub body was able to be squeezed more in the center which would actually make the ends go bellmouthed. With such a short flange only being held in by sketchy glue it would have popped like a cork.
I completely agree about the bell mouth ends I think this probably never happened in their simulations because of some dodgy FEA. I’ll probably make another video including the latest findings from the investigation.
Good video! For consideration, forgoing the predominant error regarding use of Carbon Fibre tow axially wound as a total misapplication of engineering principles, the geometry of the mating surfaces between the titanium ring and hull was completely misunderstood by Stockton-the-Princeton-engineer as well.
Jamie, this is so far the most factual analysis done about this accident. Most of the videos posted are mere opinions. You point out aspects that are not far from the cause of the accident.
Also what about the microscopic bubbles that are cured into the matrix as the epoxy cured? a pressure vessel that sees the extreme pressure that that hull did would compress and uncompress with each dive breaking strands of fiber with each cycle. He heard this crackling and yet he did nothing to address it.
Very interesting: It's actually worthwhile to know in detail what you're doing. Impressive knowledge, Sir!