Delamination is when layers of carbon fiber begin to unbond from eachoher due to stress. Steel returns back to its original shape. Damage to carbon fiber remains and accumulates. That's why the Titan could make multiple successful dives before imploding. Also, carbon fiber holds INSIDE pressure well because the tensile strength of the fibers is incredibly strong. Outside pressure on carbon fiber will put more stress on the epoxy that the fibers are suspended in, which will necessarily promote delamination. Imagine a barrel wrapped in ropes and glue. You can't stretch the barrel because the ropes hold tight, but if you squeeze the barrel, the ropes fall loose and the glue breaks.
These guys love to make things that fall apart after little use. Then it's time to sell the sucker more carbon fiber things. Just like Walmart and Home Depot. Disgraceful.
How does this degradation from repeated compression and expansion cycles over time differ from that of an airplane fuselage made of carbon fiber, like the 787 Dreamliner? Is there a difference between underwater compression and atmospheric compression? How is carbon fiber safe on an airplane? Would really like to understand the difference.
@@SidGolan for instance, at a depth of only 500 feet the water pressure acting on the hull of that sub was 31,223 PSF.a much higher force than at 32,000 feet in the air.
James Cameron said his spherical titanium submersible compressed 3 inches in diameter at depth. It is safe to say that titanium and carbon fiber would compress at different ratios causing even more extreme pressure on the Titan joints that were GLUED into place. I'm impressed it didn't implode on the first dive.
yup i was just thinking the best thing for this kind of deep dive is a titanium sphere where the compression forces are distributed equally over the surface other shapes create uneven higher pressures in certain sections plus cf is not good on compression stress which is what you're dealing with in this case
There's a video where it was supposedly live video of the construction of the capsule It was nothing like this. It looked like they were winding this of wires around the core
Dude, any engineering student can calculate in 5 minutes: Compressive stress in the carbon fiber polymer (CFRP) wall of the Titan submersible was about 200 newtons per millimeter squared at Titanic depth. This corresponds precisely to the stress level where CFRP typically fails under compression. Only under tensile load (which is not applicable underwater), CFRP can withstand about 10 times more. What's more, OceanGate used unidirectional (circumferential) CFRP. This means that in the longitudinal direction, the hull was only about half as strong, at around 100 newtons per millimeter squared. It's a miracle the ship even made it to Titanic a few times without imploding.
Carbon fiber is excellent to carry tensile stress, but not the best for compressive stress, and absolutely NOT the compressive stress within the fibers plane, which is a type of stress that promotes delamination. The two hemispheres of the Titan submersible would push against the CFRP cylinder with a force of thousands of tons, almost 20'000 t every time the Titan reached 4'000 meters depth. This led to a 210 MPa compressive stress within the cylinder wall, a value which is dangerously high for CFRP. Of course CFRP can carry much more in tensile stress, but not compressive stress within the fibers plane, this is something that NOT HAPPENS in airplanes, so if CFRP is safe for airplane wings, it doesn't mean that is suitable for submersible's hull because the stress type is different! For a typical carbon fiber in epoxy matrix I would not exceed 50 to 70 MPa of cyclic stress in that direction, so a submersible with that design should not dive deeper that 1'000, maximum 1'300 meters in my opinion. But I don't know what kind of CFRP the hull was made, I am doing assumptions basing on a commonly used CFRP type, maybe they adopted a fiber design specifically optimized to withstand compressive stress, who knows? In any case, a designer should know exactly WHEN the vessel collapses, so a destructive test should have been carried on before using it for carrying passengers: basically you dive the submersible deep down until it implodes. Then, if the submersible implodes e.g. at 5000 meters, you can assume that, in order to be safe respect to fatigue stress, you should not exceed 30% of the collapsing depth. I say this because you can run, of course, simulations, but in the simulation it's difficult to keep into account all the possible material defects, so a destructive testing campaign would give the most reliable result. And you SHOULD KNOW exactly when the failure occurs, it's a vital information! Then, I would also not use CFRP at all for that application, CFRP is anisotropic material, in that case stress comes from any direction and therefore an isotropic material, i.e. a metal, suits better. They made the hemispheres in titanium: so it would be a good idea to make the cylindrical section in titanium too. In this way you also avoid the mismatch in material's elastic modulus, which leads to additional stress in the junction area between CFRP and titanium, which is another possible source of delamination. P.S. I'm an automotive engineer with 15 years of experience Edit: I have found a video, you can watch it at the following link, where they compare the compression resistance of tubes made by different materials, including a CFRP. I don't know what type of CFRP and if comparable to the material used in Titan hull section, as details of materials used in the video are not given. Anyway, the CFRP tube collapsed at 2998 kg, that is equivalent to a pressure of 203 MPa for that pipe geometry. I wrote that Titan reached about 200 MPa of pure compressive axial stress every time they dived till the Titanic depth, so now you can realize how close they were to the compression limit of CFRP. Fatigue stress probably added delamination spots every time in a cumulative damage to the hull, so that section after ten dives was definitely not the same as the first dive. Considering these numbers, it's surprising they have been able to dive several times before the collapse of the hull th-cam.com/video/PlvyZ1r1DCM/w-d-xo.html
IKEA has drawers doing non-stop open/close cycles to prove their durability. Ocean Gate should have had a 2nd Titan doing simulated deep dives in a pressure chamber
Human arrogance at its finest. If you want to experiment with your own life that’s one thing, but to be allowed to experiment with the lives of other’s is morally unconscionable. This submersible was a death trap waiting to happen. Even if the other passengers signed a waiver to acknowledge the risks, none of them fully understood just how poorly designed the submersible was. After listening to the experts in the field and gathering more information about the history of deep submersible diving, this situation was 100% avoidable. Stockton Rushes legacy will forever be tainted by his deliberate carelessness and refusal to do things the right way. There was a clear standard set in place for safety that had been tested and proven. The fact that Stockton knowingly went against that system by cutting corners at every opportunity he had to do the right thing is criminal. No one had to die and that is what makes this situation so tragic.
I'm sure some psychology students must be interested in the Titan tragedy as a conversation starter about things like narcissism, human hubris and wishful thinking.
I believe that there is a degree of latent strain within the CF during the Winding Process - when manufacturing a heavy CF Cylinder. The CF material is wound to form a Cylinder under some winding tension. Over the course of many layers, this internal tension increases, (rather like wrapping an elastic band many times around your finger). This winding tension becomes compound, thus the internal layers suffer high degrees of latent strain. I am not exactly certain - if there is any "normalisation" process that could be applied in order to unify the newly-formed CF Cylinder, in order to relieve those inherent internal stresses........created in its' manufacture. It was your positive attitude and comment that compelled me to write down my thoughts. Greetings from Australia.
You make a great point. As a layperson and know nothing about this type of science and engineering I have learned more from this single thread on youtube than any other reading I have done about carbon fiber, it's been great, really enjoying learning new things. Given me a lot of respect for these engineers that know such amazing things.
Okay, but I want to point out that in airline applications the inside might be at surface pressure (say ~15psi) and the worst the outside can be is a vacuum or 0psi. This means it has to withstand at most 15psi outward pressure, pulling the fibers lengthwise. The Titan was heading towards 5672psi inwards pressure compressing the fiber. Use correct materials in the correct appliction.
OK genius, there are thousands of carbon fiber scuba tanks which are used in deep sea applications daily. They are similar shape and have been around for decades. Please explain this anomaly in your thought process
@@gbear1005 Yes, internal pressure higher than external pressure. (Or you could not breath out of it.) Those tanks are not meant for higher pressure outside than in. Neither do they go to 4km depth.
After the Titan disaster I saw a TH-cam video where they test the compression test of various material using a hydraulic press. The sample were basically 1 inch diameter tubes and about 2mmm thick from memory, and about two to three inches long. They were stood upright under the press head and the pressure recorded when they began to collapse. The interesting was that carbon fiber was one of the materials tested and it was only about twice as strong as aluminium! The strongest by far was stainless steel which suprisingly even outperformed titanium!!
Carbon fiber is the last thing I would decide to make something like this out of. It has awful compressive strength, especially when you're taking it thousands of feet underwater. How did this even get passed as a good idea
One of the design issues not pointed out is that the CF was wound around the hull axially, meaning that the only thing resisting the longitudinal stresses was the epoxy.
Interesting. I’ve heard experts in other interviews point out that carbon fiber performs excellently under tension (as with planes) but not always as well under compression (as with the submersible).
Exactly, that is the point he conveniently leaves out. CF is not some magic 'do it all' material, it has strengths and weaknesses and is very light. And it isn't 'modern' either - it has been used in sporting goods since the late 70s.
In summary, the higher it goes in the atmosphere the less atmosphere pressure. The deeper it goes in the ocean the higher the pressure, exponentially. The 2 are not comparable…
Strength is relative to weight.......Specific gravity of Epoxy/Carbon matrix is only 1.6 and 7.6 for steel.......Was weight critical..???...........I do not know.......For it's weight carbon is hard to beat.......1/4th the weight of steel..........Even aluminum is 2.6...................Paul
As an engineer it beyond reasoning why someone would want to use carbon fiber to build a submarine when it is an unfit material to use under compression. Foolish pride and not listening to the experts to use the right materials was what got the CEO killed and unfortunately the passengers. Hope this will be a lesson to others to listen and get expert help always and only use certified crafts or equipment.
I am an electrical engineer so I am no expert in material science, but I have worked with mech engineers my entire career. Most electrical circuits need a housing and environmental protection. The carbon fiber hull would have raised my flags right away. Did Oceangate even know the CTE of the poduct they used, it varies widely with manufacture. I would have never gone on a dive. Let alone the fact that I don't have a spare 1/4 million anyway.
The ceo supposedly had an engineering degree from Princeton. Maybe he was suicidal. And I'm shocked that billionaire passengers wouldn't have hire their own 3rd party certification. Maybe everyone was just really dumb
@@sdrc92126 just because he had a degree in engineering from Princeton doesn't mean anything, there are good and bad people in all occupations plumbers, nurses, Carpenters,ect.
@@karlmiller7500 It means either princeton is terrible or he didn't listen or he was insane (my vote). This is taught in at least 5 classes to get an *ELECTRICAL* engineering degree much less something more applicable like mechanical, aerospace or civil engineering.
I don't trust the material on bicycles because they'll eventually give way. I definitely don't trust it to be used in a submarine. They'll break without warning if cracks isn't spotted early.
There was a fatal incident several years ago in my state when a cyclist's carbon fiber bike frame broke apart when he was cycling at speed. Plus a good number of injuries.
@@jonathantan2469 Yikes. Fatal you say? All the more reason why an aluminium bike will last forever even when stored as opposed to a CF bike. No thank you.
"under 13,000 feet of water" The Titanic wreckage lies at 13,000 feet on the Ocean floor. The Titan was nowhere near the Ocean floor when it imploded, according to the Navy who picked up an implosion noise in the vicinity shortly after contact to the submersible was lost, around 1 hour and 45 minutes into the usual 3-hour-long descent of the Titan. So, the implosion likely happened somewhere around 7,000 feet under the Ocean surface.
@@CC3GROUNDZERO Paul was wrong, the website states the descent and ascent takes 8/9 hours. Therefore a descent would require 4 and a bit hours, whereas they were in the water for 1 hour and a half before implosion. Thus they were nowhere near the Titanic before the incident. The ship then fell to the seafloor, about 500m (1600ft) from the Titanic (still no where near it).
@@TopFix There are indications that the descent rate for this dive may have been more rapid than planned (if the transcript of the comms is authentic). That would suggest that they may have been near to the Titanic when the problems started. Supposedly, they shed the ballast and, but still failed to rise significantly before the failure occurred.
It might not have been the carbon fibre that gave way - but the interface between the carbon fibre and the titanium rings holding the end caps on. Two dissimilar materials with very different mechanical and physical properties bonded using glue and put under repeated stress cycles - what could possibly go wrong.
From what I understand is that the material is better at inside presure not outside presure pushing in. So it's perfect for going up things like planes and spacecrafts but not submarines.
Not much differential pressure for an airplane either. The cabin is about 10psi while at 36K feet the outside air pressure is about 3.7psi. For the sub, outside pressure is about 6000psi. If they are at one atmosphere inside the sub it would be 14.7psi an enormous differential.
Steel is great for hulls. If properly designed and tested. The ideal design is one that works for the application. Submarine specification has depth and pressure limits. Imagine going beyond the limits and just like the movie but real life.
So why would they have chosen to use carbon fiber? Did he think it would be an alternative? At this point shouldn’t it have been an already proven science that only titanium will work for all subs and everything else will fail? Why was there still people guessing around about it?
Carbon fiber is really two things, the carbon fibers themselves and the resin that holds the fibers in position and gives them stiffness. Carbon fiber has a tensile strength of 3 - 7 Giga Pascals. The tensile strength of resin is 55 Mega Pascal to 2.7 Giga Pascals. So the tensile strength of resin is below that of the fibers. Under expansion, as in a tank filled with gass and pressure pushing out, the fibers are taking all the load and the weave helps the fibers stay together and the fibers strength against stretching prevents explosion. However, if the pressure is outside pushing in, it is the resin ( and not the fibers) that take the load to keep the fibers from bending. The strength of the fibers in this case is less important. The other issue is the viewing port was rated for a depth of 1800 meters, but the Titanic is located at about 3800 meters. So the implosion could also have been due to the viewing port itself.
@@waitandhope When products are tested generally they are tested to conditions that surpass the working conditions. I think engineers use 10x the expected load. Also, tests involve re-examing the structure after testing to see if micro fractures, not otherwise visible are present, because it is possible for a structure to accumulate stresses passing X number of tests but failing after X plus 1. I understand that ultrasound exam of the hul was not something done with the submersible Titan, and it was not tested to the 3800 meters that is the depth of the fated trip. Certainly if one knows the stress of the weakest link, in this case the resin, and the thickness was increased to compensate, it could have survived. But that thickness could also introduce more complications not to mention cost, weight, reduced interior volume or increased size (the submersible has to fit on a mother ship), and possible difficulty fitting the various windows, hatches, and accomodating all the accessories that have to go through the wall and still be water tight to large depth.
@granitfog that is absolutely false, or else you'd never have any bending applications of composite materials!! (like airplane wings....) . The layup was undoubtedly a quasi-iso layup, thus having fibers in all directions and capable of handling load in all directions (not just in plane of the laminate, but compressive and tensile). The matrix transfers the load to the fibers, and they take the majority of the load due to high stiffness.
@@josephgarrett3075 "Bending" involves a force applied from one direction resulting in tension and compression being experienced from opposite sides of the material simultaneously. So, the tension resistance of the carbon fibers on one side, conteracts the compression resistance the resin on one side. A cylender with force applied externally from all directions, results in compression being applied simultaneously from all directions. This precludes tension resistance on one side from conteracting the compression of the other. All fibers in all directions experience compression. Since carbon fiver has the lower ability to resist compression, it is up to the resin to prevent failure. (Mass Inst Tech: "Epoxy is strong in compression, but weak in tension, and carbon fiber is strong in tension, but weak in compression, but the combination of the two is strong in both" when the direction of forces allows the advanages of both to manifest.) The relevant factors in this particular case is that the force (compression) is applied from all directions simultaneously, reducing the advantages of carbon fiber.
It's the wrong material for subs. Under sustained load in the presence of sea water, carbon fiber's tensile strength decreases 7 to 12%. Wet/dry cycles also weaken it. Every time he took that contraption down, he was one day closer to death, because he was weakening the hull. Then you have those titanium end pieces that were glued to the carbon fiber with epoxy resin aka JB weld that you can buy at auto zone. Epoxy resin has a tensile strength of 5 to 6000 psi, but the Titanic depth he took it down to, has a pressure of 6000 psi, not good. If that wasn't crazy enough, they said the plexi glass portal was only rated for 2000 or so feet. The manufacturer told him this, but he used it anyway. There were so many weak points on that thing, that there's no telling what caused its demise. They said the last message he sent was that he was dumping ballast weights, so something happened to cause him to try and resurface. He probably sprung a high pressure leak in one of those end piece joints or carbon fiber stress cracks that the Brit found, and it was the beginning of the end. He fired the Brit for telling him it was unsafe and there were stress cracks. I could be wrong, but I think the thing exploded instead of imploding. If the pressure leak started in a compromised area and the rest of the contraption was sealed up, the pressure would have exploded the cylinder like compressed air blows up a tire. I suppose the bodies inside would have imploded though. The kid was the only one who had any sense and didn't want to get on the rinky dink thing. The said he did it anyway to bond with his dad, which seems strange. I thought you bonded with your dad, because he was your dad. Why would you have to risk your life to bond with your dad? I used to go fishing with my dad, but never considered it a bonding session.
You make good points, I wonder if he'd just used a thicker hull than 5 inches if it could've held together. Maybe more like 10? The reason he wanted carbon fiber was so he could fit more people into it. It's all explained in his speech somewhere. This was the 2nd version of it, the had an earlier one using steel or something that wasn't designed to go that deep. Besides all that an expert said he should've been charging 1 million then decommissioning the sub once it reached its dive limit and built another. Sounds like he wasn't willing to keep rebuilding the thing like that.
Some good points here, but it is incorrect to equate the pressure they were underwater to the tensile strength of the epoxy (meaning that the epoxy was experiencing 6000psi just because they had an external load of 6000psi). That has to do with load distribution and design, not the external load.
How would it have exploded like a car tire? The difference between a container's internal and external pressure is called the differential pressure. A car tire can explode if the differential pressure gets too high and exceeds the ability of the tire to contain the pressurized air. In order to increase the differential pressure enough to explode the tire you will need a compressor to force enough air to go into the tire while the pressure outside the tire remains the same. In the case of the submersible, the only available pressure source is the ocean outside. If the sub sprang a slow leak the highest the internal pressure could ever go would be equal to the outside pressure. If that had happened the sub would never have exploded or imploded. It would have just slowly filled with water until the occupants inside were either crushed to death or they drowned. The only other thing that could have happened would have been a catastrophic implosion where the hull suddenly failed and everything was suddenly forced inward. During the implosion the pressure inside the sub would have instantly become equal to the pressure of the ocean. After the implosion the sub would have ended up as a twisted, broken mess, which is exactly what we're seeing as the wreckage is being brought up.
Most epoxies have a tensile strength of 10,000 Lbs and compressive strength closer to 20,000........The specs are readily available from each manufacturer.........I have been using and researching the stuff for more than 30 Years..................Paul
The point this misses is the strength of the points where the carbon fiber was bonded to the titanium end caps, and the fact the carbon fiber was shaped into a tube rather than a sphere which is less sturdy. I've seen that the sub had some sort of sonic safety system which monitored the carbon hull and it picked up warning before the implosion.
The other thing to is that metals will strain harden... actually get stronger before giving out and breaking. Composites like this just get weaker and weaker as the damage accumulates.
The engineer failed to mention that anisotropic materials like composites are generally much strong in tension than compression and thus a more obvious choice for aerospace fuselages than submersible hulls.
Rich people will fight with a cashier if they get overcharged a quarter. Why the hell would this guy spend $20K on an ultrasound for his toy? The biggest penny pinching tight wads are the rich.
That's a psychological side-effect of being rich. It's either because they used to be poor so they can't chill when it comes to money or they believe everyone is out to rob them or they think that being rich makes them wiser/smarter than everyone else so they know best or they're just plain old addicted to money/greedy and every cent they loose is like their life force draining away. You unfortunately don't have to be very smart or wise to get rich and that's why they end up doing really stupid and irresponsible things but everyone else can learn from their mistakes so on the whole I guess it kinda evens out. It's also very difficult for us plebs to sympathise with the people who lost their lives because we expect them to have known better.
It's likely the operation wasn't efficient, costs might be high to conduct every tour. 250k per person may have been just enough to come out with enough profit to continue the tours. The CEO tried to utilize items you can get on Amazon or a camping store. It's similar to being "house poor" when all your money goes to the house payments for a fancy house, but the rooms barely have furniture. I give him credit for pushing the envelope for a new type of exploration, but not investing in an ultrasound prior any tour.
It also looked like they screwed brackets into the CF hull on the inside, if so that would compromise the structure. Also any materials engineer would understand CF strength is tensile not compression, such a sad waste of lives :( !
That's the key. Titan never went through an autoclave oven under pressure to secure the fiber and resin composite into a bonded structure. Big autoclaves are rare, but I'm sure they exist somewhere. Having done that step the hull may very well be safe and reliable. If you cut too many corners you have nothing left.
It surprises me that there's no mention here of the fact that composites can be unpredictable when they're under compression - like in the skin of a submarine. In the Boeing 787, or any jetliner, the fuselage is pressurized from the inside - the cabin has to be under higher pressure than the outside air to allow the passengers and crew to breathe without oxygen masks. That means that the entire skin of the pressure vessel in an aircraft is under tension - which is when carbon fibre is at its best. Under the sea, the pressure is far greater on the outside of the submersible. The sea is squeezing the pressure vessel from all sides, placing the carbon fibre under compression from all angles. This introduces all kinds of hard-to-predict failure modes. I learnt this stuff during my aeronautical engineering degree quite a few years back and I'm really surprised that this isn't talked about more in relation to Titan.
In that foggy cool room, there are prepregs, pre-manufactured plates of carbon fiber (canvas or twill) with resin. They shape them in the form (using press or vacuum) and then bake in furnace. This is why it must be stored in cool. You cant made a monolitic object. The titan sub was made different technology - raw fiber wraped up very simply way around the form, resin was applied with a spatula by hand.
There was nothing wrong with the Titan submersible's engineering, in my opinion. It just needed to have an expiry date, a service life (I'd say no more than 1 year), or a fixed number of dives before it was tossed and replaced. At such high pressures (400 atm), latent signs of stress and hidden microcracks had likely begun occurring. This happens to other high-strength but frequently-stressed items we use like bike helmets, kevlar vests, shin guards, roof, tires, etc. If the sub worked safely that many times, then the technology was not flawed per se. Deep water pressure didn't just magically increase overnight. The sub's number of dives just needed to be limited. Everything engineered by humans lasts only so long. So for the quarter million dollars they charged each passenger and their one million in build cost, the sub would theoretically have paid for itself after four passengers or a single full-cabin dive.
I think his plan was not for the hull to keep up for as many dives as an all metal hull, in fact he had already scrapped one hull that showed signs of cyclic damage. His plan was to detect the early signs of damage well in advance with the acoustic detector he had patented and had installed on the Titan. Maybe it was a combination of the hull not holding up as well as he thought plus the detector not detecting as much as it should.
@@sigkilFollowing Rush's logic, airlines should skip the 100 hourly inspections and instead install detectors which will let you know in-flight when your wings are about to fall off.
Even if not specifically the carbon it’s probably either the interface of the titanium and carbon fiber or the porthole. The different materials strain and deform at independent rates. The design was flawed from the beginning.
If the window failed before the carbon fibre, then the carbon fibre cylinder would have likely remained in one piece since the pressure inside the sub would then be about the same as outside.
I wondered about that, too. I assumed that she meant that not necessarily was the hull the cause or the thing that went first as opposed to the port hole but that at some point in the implosion at least, the hull did give way/tear apart/fail. But yes, I would have found a different way to phrase that altogether.
The "latest, greatest space-age material" doesn't mean it's appropriate for extreme high pressure applications. This guy is a salesman first and foremost.
As someone who uses structural adhesive to bond CF and Titanium together I'm left wondering if they primed the Titanium. Without a primer there's very little durability or strength in the bond.
Carbon fiber works well for dream liner , because it has a pressurised cabin. More pressure inside , less pressure outside. In case of Titan the situation was reverse ; less pressure inside , more pressure outside.
Aerospace applications: tensile strength, carbon fiber Deep Ocean applications: compressive strength, not carbon fiber anyone working on a submarine should have these basic concepts understood.
Bangs they said was the pressure of the hull. So the hull would adjust and possibly weaken creating new stress points. Stockton said, when things fail, thats when it gets interesting.
Does anyone know how you autoclave a 5 inch thick section of carbon fiber? How long of a vacuum period does it need to evacuate air voids? I’ll add are 5 inch thick carbon fiber parts a thing?
On second thought...the Titan collapsed at 13,000', after several trips to the bottom (and back up).... that's actually a very good record for what was essentially a backyard build. I'm not an engineer or anything, and certainly there could've been a bit more safety research on it, but it seems to me that carbon fiber may have some potential uses for underwater stuff. Like fixed structures, underwater domes, etc.
Unfortunately I think Stockton Rush was using those prior dives as "proof" that his sub could continue to dive. But even he (and passengers) heard cracking noises, and he knew those noises were carbon fibers breaking. He should have known his sub was really a ticking time bomb with a limited life. It was as if he was trying to squeeze out just a few more dives. Was the guy in debt or something?
NDT would've revealed nothing, because the carbon fiber itself wasn't the least bit defective. What was defective was using it in a compressive application, rather than the tensile applications it excels at.
No one seems to be talking about the vessel having a titanium ring GLUED to the Carbon Fiber Hull. When is Glue sufficient to withstand deep sea pressures? Anyone? You cannot tell me Glue was not the weakest link!
This "specialist" seems to not understand the main cause of the Titan accident - the fact that carbon fibers are good at tension but not at compression.
Why not have an aluminum backed carbon fiber? Like a liner to protect the actual carbon fiber. Or steel or something. The other material won't be for the strength. No gap between it. Just to protect against scratches and gouges. The other material will be the outside liner.
Remarkable that the hull failed at (according to the reporter) 13,000 feet, a full 500 feet deeper than the ocean depth at that point. Did the sub have a digging feature or is the reporting here just utter garbage.
20'000 for a stress test. That's nothing to billionaires. That's just stubbornness and denial by Stockton Rush/Oceangate. Oceangate really could have been at the cutting edge of innovation if they tested it all properly and without tourists until they were sure, but I don't think the sub would have done well in tests. I have this horrible idea he didn't want it testing for this reason. It was all about the money and fame. People who do things and take risks without taking into account the safety and welfare of others often fall apart in the end. The bigger they are the harder they fall.
Vacuum of space versus Titanic depth is 400 times ratio Fibers work in tension not compression. Basically the Epoxy adhesive is doing the job. 2 same pressure vessels on earth at 14.7 psi inside. One is going to Pluto and seems a mighty 14.7 psi pressure with the vacuum of space. The 2nd vessel is only going to see the Titanic so has 395 times the pressure since it is 5800 psi there. The Titanic pressure vessel is using epoxy to hold the 5800 psi outside and the carbon fiber is just marketing hype. Ie giant red flag that none of that fiber is really in tension. Maybe some pretension but still hokey stuff
You completely missed the most relevant point that fiber composites excel in tension, not compression; that its use in this way is fundamentally unsound. Mark Shinnick
Wound layers of fibres will be under shearing forces just from variations in ambient temperature - although carbon fibre has a low coefficient of thermal expansion it's not zero, outer layers have a larger circumference and thus a greater length of material per winding than inner layers, and are thus subject to more expansion and contraction for a given change in temperature than the inner layers. Even without the stresses of repeated deep-dives the previous year, if the sub wasn't stored in temperature-controlled conditions then it was probably weakening with each passing day regardless.
Hello everyone I’m going to ask a very silly question, I’m very curious about science but I can’t understand most of it. My question Is the following, why didn’t they cover the carbon fiber with another material like plastic do that way the water won’t get inside and laminate the carbon fiber??
Carbon fiber is the tensile component of a composite. External pressure places it into compression and the epoxy into tension. This sub never went down more than a few hundred feet.
Carbon fiber composite hull is better suited for pressure from the inside (like the hull of the Boeing 787) than enormous outside pressure (like the hull of the Titan submersible). Not even considering the enormous force that the two hemispheres at both sides of the hull put on the carbon fiber structure.
Reports state the implosion happened within a fraction of a second. That's not to say the crew didn't hear the terrifying sound of the carbon fibre hull cracking prior to it (as was reportedly heard by other crews on other missions). One ballast was missing from the sub when found so they knew something was wrong and were attempting to re-surface.
or else when the implosion occured the ballast just detached. also there was no way even if all the ballast dropped for them to get to the surface so fast. the support ship would have heard the implosion hence why they delayed eight hours. they had to change their pants and start shredding documents
@toomanyaccounts latest reports are, there's no way the mother ship didn't hear the implosion. It was equivalent to a major TNT explosion. Lots of cover-up going on. We might have the final truth a year or two from now once public emotions have died down.
A tourist sub going a few hundred feet under water could absolutely be built out of 5 inch thick carbon fiber. Like 300 feet to see pretty coral reefs.
The great difference between aerospace application and the Titan submersible application is pressure. In space the maximum pressure difference with reference to sea level is 14.7 psi. That's it. In deep submergence activities the pressure differential increases by 14.7 psi every 33 feet of descent. The Titanic is at 12,500 feet below the surface. That amounts to 5568.18 psi, pounds per square inch when a vessel is 12,500 feet below the surface of the water. Now multiply that value by the overall surface area in square inches of the composite shell of Titan and you come up with an astounding amount of pressure. Carbon fiber is a non-homogenous material. It's components will flex at varying rates according to how pressure and stress are applied. Steel and titanium are homogenous, all one material. It all reacts the same.
What would we expect from someone with contempt for "50 year old white guys" regardless of their knowledge, experience and accumulated skills? It was a 50 something year old white guy who landed an Airbus on the Hudson River with zero loss of life.
first off carbon fiber is 5 times stronger and lighter than steel. however carbon fiber is only strong like that under tension, not compression like in the titan sub. 2nd that 2 story oven is called an autoclave. autoclave is used to add heat and pressure to the part while the part cures, this removes air bubbles trapped in the resin
Note, he was showing carbon fibre woven sheet ..not yarn wound in a single direction which was the ridiculous way that sub was built. Even toilet roll tubes are spiral wound!
I dont understand why this whole submarine thing is going so viral on the internet to this extent, it almost seems like a manufactured scenario being pushed out onto society for whatever reason 😂
That engineer did not mention that carbon fiber composites are strong under tension but weak under compression. The submersible was under compression. Carbon fiber was a very bad choice for the deep sea dive application.
Carbon fiber is only very strong in tension. Pressure from outside the sub's hull put the fibers in compression. CF was nothing more than a filler for the epoxy resin which had some strength due to being five inches thick. The sub imploded because the fibers were asked to be strong in compression. The sub would have easily contained the pressure at that depth only if the pressure was on the inside of the hull. A solid fuel rocket motor with a carbon fiber casing contains the pressure because the CF is stressed in tension. It is the difference between pulling on a string and pushing a string.
They apparently only got 3/4 of the way down before they got warnings and cracking sounds, and dropped their "ballast" weights and steel frame and tried to go upwards. But about 20 minutes later the craft imploded. That is the latest info I have fwiw.
Didn't Stockton Rush screw his monitors to the inside of the carbon hull with screws. I saw that and I thought that couldn't be healthy. I'm sure there'll be a report on the cause sooner or later
Carbon fiber works better in tension vs compression. In an aircraft, weight is a huge enemy and the plane is internally pressurized though not by much. The titan sub was under immense compression.
Carbon fiber cloth bound with resin. Interestingly I read that the right kind of resin one should use to lay up carbon fiber is epoxy resin. I make split cane fly rods (bamboo) and glue up the sections with two part epoxy resin. The resin is very strong but movement of the bamboo under stress, such as casting or a fish, puts shear stress on the bamboo. Epoxy also needs the correct temperature to cure properly. Split cane rods are usually cured in a heat treating oven. In essense the glue can be stronger than the bamboo, but I don't think I'd trust it 12,500 feet below the ocean with repeated stress in a submersible.
You are correct about epoxy resin. At very low temps, it is extremely brittle. The thickness of epoxy (at each Bond Layer of CF) would be measured in micrometers. Epoxy Bond (at that bond thickness) and at 4 degrees C, would quickly develop stress cracking from the natural flex of the Cylinder under great pressures, and then returned to atmospheric. This is how I believe the disaster happened. CF composite became weaker upon each dive. It had to be the reason. Those 5 persons still weighed their true weights, inside that Capsule. The downward force (weight of 5 people) would have also placed an uneven stress on the internals of the formed CF Capsule, giving the cylinder tendency to take on a slight elliptical. Not certain if payload was factored-in during design, or how the flat floor was secured to the Cylinder. RIP to those pioneers who won't be forgotten.
@@peterduxbury927 Added to that, the carbon fibre was rolled on circumferentially, whereas best practice is to lay up alternate layers diagonally so that the material is equally strong in all directions. Further, the construction was carried out in a large, probably dirty and dusty workshop and there were no processes for degassing the resin, so the layup undoubtedly included dust and dirt and air bubbles, all locations where failure cracks would start to build up.
@@Smannellites I have to agree with you that when laying the CF material, it wasn't cut (or wound) on the bias, but wound circumferentially, with yarns laying upon yarns, with air bubbles locked-into the whole formation. Clearly, an inherent longitudinal weakness in its' design. I also observed the methods of cleaning the titanium annular ring (for the bond between the CF and titanium). A wipe around the ring with (what looked like) an old cloth with possibly contaminants! I also observed that the depth of bond between the titanium end-cap and CF Tube was nothing more than 50mm! Even Stockton Rush commented about this. It is good that many engineers can come together, pass comments, even though we (personally) have no hope of ever building something so unique, it CAN pass all Safety Testing with flying colors! Without Carbon Fiber as a structural element! But (to me) there were many errors that led to this tragedy. I believe that the distant future will provide us with vessels that can reach those 4km depths, carrying paying passengers too, and not just around the Titanic.
I'm not an engineer, but I understand fibers perform well in tensile, not in compression. An airframe has to take expanding pressure from inside in tensile at less than one atmosphere. The Titan Imploder had to take a ridiculous amount of pressure in compression. The basic problem comes down that they used tourist trips to the depths to pay the costs of research in the depths. Research in the depths is far better carried out by ROVs. ROVs needn't be built to accommodate humans and human lives aren't threatened. There needs to be another funding mechanism for people who have a lot of money to be able to participate in deeps research using ROVs and maybe bringing stuff up for their collections that going down themselves.
Watching the video of the spooler wind the fuselage on that OceanGate vehicle gave me the 'willys'. It was wrapping in one continuous motion, which is NOT how that should be done for maximum distribution of forces. It is typically done in an 'X' pattern to support the previous lay up.
Nope they did not, also Rush said to one of his customers that the carbon weave was obtained cheaply through Boeing due to i being out of date and could no longer be used for aviation. The hatch hemisphere has 18 bolts but they only ever used 17 due to one of them being a pain to access. Also the titanium rings that support the hemispheres were epoxied to the hull, two different materials that expand and contract at different rates. How rush described the hull cracking sounds of previous dives proves that he does not have sufficient knowledge of how carbon fibre behaves. Every time he heard those cracks at different depths weakened then hull every time on top of the usual stress fatigue. Rush dismissed these cracking noises as the the hull just “settling in” as voids in the lay up filled in and weak fibres got torn. One engineer that worked for Ocean Gate tried to raise these problems and was fired from his position. Another previous engineer also said that due to the characteristics of carbon fibre the hull monitoring system would be useless in an emergency and could never allow sufficient time to surface the sub. There are many other construction factors too.
@@Just_Another_Viewer This is going to show up in a lot of engineering ethics material I'm sure. Hopefully, at the very least, this makes a lot of engineers to check their own due diligence.
Using carbon fiber like in an airplane is not dangerous because of an open space while using it underwater and submerge it as deep as you can will pose a problem because water is not an open space. The pressure it will give are very tremendous.
theres a YUGE difference between aerospace composites and deep sea composites.. even outer space is only 1 atmosphere or 1 bar difference than earth.. every 30 ft is an extra atmosphere or extra bar of pressure under water.. thats 1000 bars down near the titanic.. insanity
The greatest irony is, that Titanic itself sunk mainly because people's pride and overconfidence came before reason, knowledge and facts. Like Titanic, the worst case scenario was mainly ignored, because it was identified as an obstacle for business and public image of the vessel, the company and the brand. Like Titanic, most of the people that died were invited or payed for the travel. Unlike Titanic's demise, that took hours, Titan was destroyed instantly. Makes you wonder, if all these people that went down there, really cared about the tragedy and what caused it, rather then just being curious adventurers that wanted to do something only very few get the chance to.
Carbon fibre and fibre glass have both been used in boats. They both deteriorate over time. It seem likely that if you use these materials under far grater stresses that they will fail a lot faster.
Delamination is when layers of carbon fiber begin to unbond from eachoher due to stress. Steel returns back to its original shape. Damage to carbon fiber remains and accumulates. That's why the Titan could make multiple successful dives before imploding.
Also, carbon fiber holds INSIDE pressure well because the tensile strength of the fibers is incredibly strong. Outside pressure on carbon fiber will put more stress on the epoxy that the fibers are suspended in, which will necessarily promote delamination.
Imagine a barrel wrapped in ropes and glue. You can't stretch the barrel because the ropes hold tight, but if you squeeze the barrel, the ropes fall loose and the glue breaks.
These guys love to make things that fall apart after little use. Then it's time to sell the sucker more carbon fiber things. Just like Walmart and Home Depot. Disgraceful.
The reason you stated alone is why it should never be used for such applications. Unbelievable! 😶
@@thinkcasting3182Are you brain damaged? What are you even talking about?
How does this degradation from repeated compression and expansion cycles over time differ from that of an airplane fuselage made of carbon fiber, like the 787 Dreamliner? Is there a difference between underwater compression and atmospheric compression? How is carbon fiber safe on an airplane? Would really like to understand the difference.
@@SidGolan for instance, at a depth of only 500 feet the water pressure acting on the hull of that sub was 31,223 PSF.a much higher force than at 32,000 feet in the air.
James Cameron said his spherical titanium submersible compressed 3 inches in diameter at depth. It is safe to say that titanium and carbon fiber would compress at different ratios causing even more extreme pressure on the Titan joints that were GLUED into place. I'm impressed it didn't implode on the first dive.
yup i was just thinking the best thing for this kind of deep dive is a titanium sphere where the compression forces are distributed equally over the surface other shapes create uneven higher pressures in certain sections plus cf is not good on compression stress which is what you're dealing with in this case
There's a video where it was supposedly live video of the construction of the capsule It was nothing like this. It looked like they were winding this of wires around the core
@@botgurl6583 nothing like what?
@@ARCSTREAMS maybe but titanium doesn't take the repeated cycles of compression and decompression too well. even if its strong to start with
Does he make the same excuse when he jumps in a cold swimming pool? "Oh it's compressed in length because of the cold!"
Dude, any engineering student can calculate in 5 minutes: Compressive stress in the carbon fiber polymer (CFRP) wall of the Titan submersible was about 200 newtons per millimeter squared at Titanic depth. This corresponds precisely to the stress level where CFRP typically fails under compression. Only under tensile load (which is not applicable underwater), CFRP can withstand about 10 times more. What's more, OceanGate used unidirectional (circumferential) CFRP. This means that in the longitudinal direction, the hull was only about half as strong, at around 100 newtons per millimeter squared. It's a miracle the ship even made it to Titanic a few times without imploding.
Yep
There was NO CFRP in the Titan........The P stands for plastic.......If You are an Enginnering Student, You are failing..............Paul
@@paulholterhaus7084 No. CFRP stands for Carbon Fiber Reinforced Polymer. Try looking things up before making a fool of yourself in public.
@@richardpare3538 Well, that's gonna leave a mark...
Its like an frp pressure vessel.
Fiberglass reinforced *plastic*
Carbon fiber is excellent to carry tensile stress, but not the best for compressive stress, and absolutely NOT the compressive stress within the fibers plane, which is a type of stress that promotes delamination. The two hemispheres of the Titan submersible would push against the CFRP cylinder with a force of thousands of tons, almost 20'000 t every time the Titan reached 4'000 meters depth. This led to a 210 MPa compressive stress within the cylinder wall, a value which is dangerously high for CFRP. Of course CFRP can carry much more in tensile stress, but not compressive stress within the fibers plane, this is something that NOT HAPPENS in airplanes, so if CFRP is safe for airplane wings, it doesn't mean that is suitable for submersible's hull because the stress type is different! For a typical carbon fiber in epoxy matrix I would not exceed 50 to 70 MPa of cyclic stress in that direction, so a submersible with that design should not dive deeper that 1'000, maximum 1'300 meters in my opinion. But I don't know what kind of CFRP the hull was made, I am doing assumptions basing on a commonly used CFRP type, maybe they adopted a fiber design specifically optimized to withstand compressive stress, who knows? In any case, a designer should know exactly WHEN the vessel collapses, so a destructive test should have been carried on before using it for carrying passengers: basically you dive the submersible deep down until it implodes. Then, if the submersible implodes e.g. at 5000 meters, you can assume that, in order to be safe respect to fatigue stress, you should not exceed 30% of the collapsing depth. I say this because you can run, of course, simulations, but in the simulation it's difficult to keep into account all the possible material defects, so a destructive testing campaign would give the most reliable result. And you SHOULD KNOW exactly when the failure occurs, it's a vital information! Then, I would also not use CFRP at all for that application, CFRP is anisotropic material, in that case stress comes from any direction and therefore an isotropic material, i.e. a metal, suits better. They made the hemispheres in titanium: so it would be a good idea to make the cylindrical section in titanium too. In this way you also avoid the mismatch in material's elastic modulus, which leads to additional stress in the junction area between CFRP and titanium, which is another possible source of delamination.
P.S. I'm an automotive engineer with 15 years of experience
Edit: I have found a video, you can watch it at the following link, where they compare the compression resistance of tubes made by different materials, including a CFRP. I don't know what type of CFRP and if comparable to the material used in Titan hull section, as details of materials used in the video are not given. Anyway, the CFRP tube collapsed at 2998 kg, that is equivalent to a pressure of 203 MPa for that pipe geometry. I wrote that Titan reached about 200 MPa of pure compressive axial stress every time they dived till the Titanic depth, so now you can realize how close they were to the compression limit of CFRP. Fatigue stress probably added delamination spots every time in a cumulative damage to the hull, so that section after ten dives was definitely not the same as the first dive. Considering these numbers, it's surprising they have been able to dive several times before the collapse of the hull
th-cam.com/video/PlvyZ1r1DCM/w-d-xo.html
Surprised I am your only up-tick.
Excellent analysis! 👍
@@wk4240 Thank you for appreciation :)
That’s the best explanation I’ve heard. This person needs more likes.
As an former Astronaut, two times Superbowl winner, Vietnam veteran and ballet trainer, I totally agree
The guy that ocean gate fired then sued was saying that destructive testing should have been performed and he said it would probably implode
IKEA has drawers doing non-stop open/close cycles to prove their durability. Ocean Gate should have had a 2nd Titan doing simulated deep dives in a pressure chamber
Human arrogance at its finest. If you want to experiment with your own life that’s one thing, but to be allowed to experiment with the lives of other’s is morally unconscionable. This submersible was a death trap waiting to happen. Even if the other passengers signed a waiver to acknowledge the risks, none of them fully understood just how poorly designed the submersible was. After listening to the experts in the field and gathering more information about the history of deep submersible diving, this situation was 100% avoidable. Stockton Rushes legacy will forever be tainted by his deliberate carelessness and refusal to do things the right way. There was a clear standard set in place for safety that had been tested and proven. The fact that Stockton knowingly went against that system by cutting corners at every opportunity he had to do the right thing is criminal. No one had to die and that is what makes this situation so tragic.
How did you find out that none of them fully understood about the poor design?
@@greyhalliwell he even lied and said NASA and Boeing were in on the engineering design.
@@greyhalliwell and he bullied the Vegas man saying that it's safer than a helicopter ride.
@@happity Did you mean to @ me?
@@greyhalliwell yes, they definitely did not understand. Only Rush was a reckless maniac.
Big difference between keeping pressure in and pressure out. Huge difference.
The only thing that kept that hull from imploding on earlier dives was the epoxy. There’s an old saying.. you can’t push a feather with a chain.
As an engineer student I love how this story has started a conversation on material science. 😊
I'm sure some psychology students must be interested in the Titan tragedy as a conversation starter about things like narcissism, human hubris and wishful thinking.
And interested by-standers
I believe that there is a degree of latent strain within the CF during the Winding Process - when manufacturing a heavy CF Cylinder. The CF material is wound to form a Cylinder under some winding tension. Over the course of many layers, this internal tension increases, (rather like wrapping an elastic band many times around your finger). This winding tension becomes compound, thus the internal layers suffer high degrees of latent strain. I am not exactly certain - if there is any "normalisation" process that could be applied in order to unify the newly-formed CF Cylinder, in order to relieve those inherent internal stresses........created in its' manufacture. It was your positive attitude and comment that compelled me to write down my thoughts. Greetings from Australia.
My thoughts exactly ❤
You make a great point. As a layperson and know nothing about this type of science and engineering I have learned more from this single thread on youtube than any other reading I have done about carbon fiber, it's been great, really enjoying learning new things. Given me a lot of respect for these engineers that know such amazing things.
Okay, but I want to point out that in airline applications the inside might be at surface pressure (say ~15psi) and the worst the outside can be is a vacuum or 0psi. This means it has to withstand at most 15psi outward pressure, pulling the fibers lengthwise. The Titan was heading towards 5672psi inwards pressure compressing the fiber. Use correct materials in the correct appliction.
"Professor, how many atmospheres can the ship take?"
"Well it's a spaceship, so I'd say between 0 and 1."
OK genius, there are thousands of carbon fiber scuba tanks which are used in deep sea applications daily. They are similar shape and have been around for decades. Please explain this anomaly in your thought process
Scuba tanks go way way way higher than 1 atmosphere...
@@gbear1005 Yes, internal pressure higher than external pressure. (Or you could not breath out of it.) Those tanks are not meant for higher pressure outside than in. Neither do they go to 4km depth.
After the Titan disaster I saw a TH-cam video where they test the compression test of various material using a hydraulic press. The sample were basically 1 inch diameter tubes and about 2mmm thick from memory, and about two to three inches long. They were stood upright under the press head and the pressure recorded when they began to collapse. The interesting was that carbon fiber was one of the materials tested and it was only about twice as strong as aluminium! The strongest by far was stainless steel which suprisingly even outperformed titanium!!
Yes.seen that too.
Good old reliable stainless steel.
Carbon fiber is the last thing I would decide to make something like this out of. It has awful compressive strength, especially when you're taking it thousands of feet underwater. How did this even get passed as a good idea
How? The CEO of Oceangate decided it was a good idea. Then he either ignored or got rid of anyone who told him otherwise.
No, NOT terrible, maybe not the very best.........Better than Wood which had supported railroad tressels for 200 years...............Paul
I don’t think they had any kind of certification.
One of the design issues not pointed out is that the CF was wound around the hull axially, meaning that the only thing resisting the longitudinal stresses was the epoxy.
Stop stifling his innovation!
Interesting. I’ve heard experts in other interviews point out that carbon fiber performs excellently under tension (as with planes) but not always as well under compression (as with the submersible).
Exactly, that is the point he conveniently leaves out. CF is not some magic 'do it all' material, it has strengths and weaknesses and is very light. And it isn't 'modern' either - it has been used in sporting goods since the late 70s.
this is a critical point that I hoped an ENGINEER would point out
In summary, the higher it goes in the atmosphere the less atmosphere pressure. The deeper it goes in the ocean the higher the pressure, exponentially. The 2 are not comparable…
Strength is relative to weight.......Specific gravity of Epoxy/Carbon matrix is only 1.6 and 7.6 for steel.......Was weight critical..???...........I do not know.......For it's weight carbon is hard to beat.......1/4th the weight of steel..........Even aluminum is 2.6...................Paul
That would be my understanding. It will stretch a little but not compress.
As an engineer it beyond reasoning why someone would want to use carbon fiber to build a submarine when it is an unfit material to use under compression. Foolish pride and not listening to the experts to use the right materials was what got the CEO killed and unfortunately the passengers. Hope this will be a lesson to others to listen and get expert help always and only use certified crafts or equipment.
I am an electrical engineer so I am no expert in material science, but I have worked with mech engineers my entire career. Most electrical circuits need a housing and environmental protection. The carbon fiber hull would have raised my flags right away. Did Oceangate even know the CTE of the poduct they used, it varies widely with manufacture. I would have never gone on a dive. Let alone the fact that I don't have a spare 1/4 million anyway.
The ceo supposedly had an engineering degree from Princeton. Maybe he was suicidal. And I'm shocked that billionaire passengers wouldn't have hire their own 3rd party certification. Maybe everyone was just really dumb
@@sdrc92126 just because he had a degree in engineering from Princeton doesn't mean anything, there are good and bad people in all occupations plumbers, nurses, Carpenters,ect.
@@karlmiller7500 It means either princeton is terrible or he didn't listen or he was insane (my vote). This is taught in at least 5 classes to get an *ELECTRICAL* engineering degree much less something more applicable like mechanical, aerospace or civil engineering.
I don't trust the material on bicycles because they'll eventually give way. I definitely don't trust it to be used in a submarine. They'll break without warning if cracks isn't spotted early.
There was a fatal incident several years ago in my state when a cyclist's carbon fiber bike frame broke apart when he was cycling at speed. Plus a good number of injuries.
@@jonathantan2469 Yikes. Fatal you say? All the more reason why an aluminium bike will last forever even when stored as opposed to a CF bike. No thank you.
"under 13,000 feet of water"
The Titanic wreckage lies at 13,000 feet on the Ocean floor. The Titan was nowhere near the Ocean floor when it imploded, according to the Navy who picked up an implosion noise in the vicinity shortly after contact to the submersible was lost, around 1 hour and 45 minutes into the usual 3-hour-long descent of the Titan. So, the implosion likely happened somewhere around 7,000 feet under the Ocean surface.
The Owner stated that the desent would require 1 hour, 45 Min...............Paul
@@CC3GROUNDZERO Paul was wrong, the website states the descent and ascent takes 8/9 hours. Therefore a descent would require 4 and a bit hours, whereas they were in the water for 1 hour and a half before implosion. Thus they were nowhere near the Titanic before the incident. The ship then fell to the seafloor, about 500m (1600ft) from the Titanic (still no where near it).
@@TopFix There are indications that the descent rate for this dive may have been more rapid than planned (if the transcript of the comms is authentic). That would suggest that they may have been near to the Titanic when the problems started. Supposedly, they shed the ballast and, but still failed to rise significantly before the failure occurred.
It might not have been the carbon fibre that gave way - but the interface between the carbon fibre and the titanium rings holding the end caps on.
Two dissimilar materials with very different mechanical and physical properties bonded using glue and put under repeated stress cycles - what could possibly go wrong.
From what I understand is that the material is better at inside presure not outside presure pushing in.
So it's perfect for going up things like planes and spacecrafts but not submarines.
Not much differential pressure for an airplane either. The cabin is about 10psi while at 36K feet the outside air pressure is about 3.7psi. For the sub, outside pressure is about 6000psi. If they are at one atmosphere inside the sub it would be 14.7psi an enormous differential.
It's great for things like fishing rods, but not for subs. You need titanium for subs.
I'll take graphite...
Steel is great for hulls. If properly designed and tested. The ideal design is one that works for the application. Submarine specification has depth and pressure limits. Imagine going beyond the limits and just like the movie but real life.
So why would they have chosen to use carbon fiber? Did he think it would be an alternative? At this point shouldn’t it have been an already proven science that only titanium will work for all subs and everything else will fail? Why was there still people guessing around about it?
Price. It’s cheaper to build and lighter to transport.
I read an account of a carbon fiber bow shattering & sending splinters into the archer's arm & body. He had to go to the ER.
Carbon fiber is really two things, the carbon fibers themselves and the resin that holds the fibers in position and gives them stiffness. Carbon fiber has a tensile strength of 3 - 7 Giga Pascals. The tensile strength of resin is 55 Mega Pascal to 2.7 Giga Pascals. So the tensile strength of resin is below that of the fibers. Under expansion, as in a tank filled with gass and pressure pushing out, the fibers are taking all the load and the weave helps the fibers stay together and the fibers strength against stretching prevents explosion. However, if the pressure is outside pushing in, it is the resin ( and not the fibers) that take the load to keep the fibers from bending. The strength of the fibers in this case is less important.
The other issue is the viewing port was rated for a depth of 1800 meters, but the Titanic is located at about 3800 meters. So the implosion could also have been due to the viewing port itself.
What'd your opinion, could this design have worked with proper testing after each dive? What if it's hull size was increased to more like 10?
@@waitandhope When products are tested generally they are tested to conditions that surpass the working conditions. I think engineers use 10x the expected load. Also, tests involve re-examing the structure after testing to see if micro fractures, not otherwise visible are present, because it is possible for a structure to accumulate stresses passing X number of tests but failing after X plus 1.
I understand that ultrasound exam of the hul was not something done with the submersible Titan, and it was not tested to the 3800 meters that is the depth of the fated trip.
Certainly if one knows the stress of the weakest link, in this case the resin, and the thickness was increased to compensate, it could have survived. But that thickness could also introduce more complications not to mention cost, weight, reduced interior volume or increased size (the submersible has to fit on a mother ship), and possible difficulty fitting the various windows, hatches, and accomodating all the accessories that have to go through the wall and still be water tight to large depth.
@granitfog
that is absolutely false, or else you'd never have any bending applications of composite materials!! (like airplane wings....) .
The layup was undoubtedly a quasi-iso layup, thus having fibers in all directions and capable of handling load in all directions (not just in plane of the laminate, but compressive and tensile).
The matrix transfers the load to the fibers, and they take the majority of the load due to high stiffness.
@@josephgarrett3075 "Bending" involves a force applied from one direction resulting in tension and compression being experienced from opposite sides of the material simultaneously. So, the tension resistance of the carbon fibers on one side, conteracts the compression resistance the resin on one side.
A cylender with force applied externally from all directions, results in compression being applied simultaneously from all directions. This precludes tension resistance on one side from conteracting the compression of the other. All fibers in all directions experience compression. Since carbon fiver has the lower ability to resist compression, it is up to the resin to prevent failure. (Mass Inst Tech: "Epoxy is strong in compression, but weak in tension, and carbon fiber is strong in tension, but weak in compression, but the combination of the two is strong in both" when the direction of forces allows the advanages of both to manifest.)
The relevant factors in this particular case is that the force (compression) is applied from all directions simultaneously, reducing the advantages of carbon fiber.
Bravo 👏 excellent information! Thanks!
It's the wrong material for subs. Under sustained load in the presence of sea water, carbon fiber's tensile strength decreases 7 to 12%. Wet/dry cycles also weaken it. Every time he took that contraption down, he was one day closer to death, because he was weakening the hull. Then you have those titanium end pieces that were glued to the carbon fiber with epoxy resin aka JB weld that you can buy at auto zone. Epoxy resin has a tensile strength of 5 to 6000 psi, but the Titanic depth he took it down to, has a pressure of 6000 psi, not good. If that wasn't crazy enough, they said the plexi glass portal was only rated for 2000 or so feet. The manufacturer told him this, but he used it anyway. There were so many weak points on that thing, that there's no telling what caused its demise. They said the last message he sent was that he was dumping ballast weights, so something happened to cause him to try and resurface. He probably sprung a high pressure leak in one of those end piece joints or carbon fiber stress cracks that the Brit found, and it was the beginning of the end. He fired the Brit for telling him it was unsafe and there were stress cracks. I could be wrong, but I think the thing exploded instead of imploding. If the pressure leak started in a compromised area and the rest of the contraption was sealed up, the pressure would have exploded the cylinder like compressed air blows up a tire. I suppose the bodies inside would have imploded though. The kid was the only one who had any sense and didn't want to get on the rinky dink thing. The said he did it anyway to bond with his dad, which seems strange. I thought you bonded with your dad, because he was your dad. Why would you have to risk your life to bond with your dad? I used to go fishing with my dad, but never considered it a bonding session.
Exactly. This isn't a safety issue or failure. The base material is unfit for it's intended use. Homicide
You make good points, I wonder if he'd just used a thicker hull than 5 inches if it could've held together. Maybe more like 10? The reason he wanted carbon fiber was so he could fit more people into it. It's all explained in his speech somewhere. This was the 2nd version of it, the had an earlier one using steel or something that wasn't designed to go that deep. Besides all that an expert said he should've been charging 1 million then decommissioning the sub once it reached its dive limit and built another. Sounds like he wasn't willing to keep rebuilding the thing like that.
Some good points here, but it is incorrect to equate the pressure they were underwater to the tensile strength of the epoxy (meaning that the epoxy was experiencing 6000psi just because they had an external load of 6000psi). That has to do with load distribution and design, not the external load.
How would it have exploded like a car tire? The difference between a container's internal and external pressure is called the differential pressure. A car tire can explode if the differential pressure gets too high and exceeds the ability of the tire to contain the pressurized air. In order to increase the differential pressure enough to explode the tire you will need a compressor to force enough air to go into the tire while the pressure outside the tire remains the same. In the case of the submersible, the only available pressure source is the ocean outside. If the sub sprang a slow leak the highest the internal pressure could ever go would be equal to the outside pressure. If that had happened the sub would never have exploded or imploded. It would have just slowly filled with water until the occupants inside were either crushed to death or they drowned. The only other thing that could have happened would have been a catastrophic implosion where the hull suddenly failed and everything was suddenly forced inward. During the implosion the pressure inside the sub would have instantly become equal to the pressure of the ocean. After the implosion the sub would have ended up as a twisted, broken mess, which is exactly what we're seeing as the wreckage is being brought up.
Most epoxies have a tensile strength of 10,000 Lbs and compressive strength closer to 20,000........The specs are readily available from each manufacturer.........I have been using and researching the stuff for more than 30 Years..................Paul
The point this misses is the strength of the points where the carbon fiber was bonded to the titanium end caps, and the fact the carbon fiber was shaped into a tube rather than a sphere which is less sturdy. I've seen that the sub had some sort of sonic safety system which monitored the carbon hull and it picked up warning before the implosion.
The other thing to is that metals will strain harden... actually get stronger before giving out and breaking. Composites like this just get weaker and weaker as the damage accumulates.
The engineer failed to mention that anisotropic materials like composites are generally much strong in tension than compression and thus a more obvious choice for aerospace fuselages than submersible hulls.
Rich people will fight with a cashier if they get overcharged a quarter. Why the hell would this guy spend $20K on an ultrasound for his toy? The biggest penny pinching tight wads are the rich.
That’s how most of them got rich
That's a psychological side-effect of being rich. It's either because they used to be poor so they can't chill when it comes to money or they believe everyone is out to rob them or they think that being rich makes them wiser/smarter than everyone else so they know best or they're just plain old addicted to money/greedy and every cent they loose is like their life force draining away. You unfortunately don't have to be very smart or wise to get rich and that's why they end up doing really stupid and irresponsible things but everyone else can learn from their mistakes so on the whole I guess it kinda evens out.
It's also very difficult for us plebs to sympathise with the people who lost their lives because we expect them to have known better.
Maybe he thought he will respawn and try again.
It's likely the operation wasn't efficient, costs might be high to conduct every tour. 250k per person may have been just enough to come out with enough profit to continue the tours. The CEO tried to utilize items you can get on Amazon or a camping store. It's similar to being "house poor" when all your money goes to the house payments for a fancy house, but the rooms barely have furniture. I give him credit for pushing the envelope for a new type of exploration, but not investing in an ultrasound prior any tour.
Down playing the need for a hull inspection, even after passengers have had heard loud cracking sounds during previous dive, was criminal.
It also looked like they screwed brackets into the CF hull on the inside, if so that would compromise the structure. Also any materials engineer would understand CF strength is tensile not compression, such a sad waste of lives :( !
That's the key. Titan never went through an autoclave oven under pressure to secure the fiber and resin composite into a bonded structure. Big autoclaves are rare, but I'm sure they exist somewhere. Having done that step the hull may very well be safe and reliable. If you cut too many corners you have nothing left.
It surprises me that there's no mention here of the fact that composites can be unpredictable when they're under compression - like in the skin of a submarine. In the Boeing 787, or any jetliner, the fuselage is pressurized from the inside - the cabin has to be under higher pressure than the outside air to allow the passengers and crew to breathe without oxygen masks. That means that the entire skin of the pressure vessel in an aircraft is under tension - which is when carbon fibre is at its best. Under the sea, the pressure is far greater on the outside of the submersible. The sea is squeezing the pressure vessel from all sides, placing the carbon fibre under compression from all angles. This introduces all kinds of hard-to-predict failure modes. I learnt this stuff during my aeronautical engineering degree quite a few years back and I'm really surprised that this isn't talked about more in relation to Titan.
the pressure at such depths as where the Titanic sits is a different thing compared to the forces applied during a flight, no comparison
In that foggy cool room, there are prepregs, pre-manufactured plates of carbon fiber (canvas or twill) with resin. They shape them in the form (using press or vacuum) and then bake in furnace. This is why it must be stored in cool. You cant made a monolitic object. The titan sub was made different technology - raw fiber wraped up very simply way around the form, resin was applied with a spatula by hand.
Yes, and it was constructed in a workshop, probably very dusty and dirty and there was no process for degassing the resin or layup.
Suppose, salt water would add to the internal tensions in the carbon fiber, too
There was nothing wrong with the Titan submersible's engineering, in my opinion. It just needed to have an expiry date, a service life (I'd say no more than 1 year), or a fixed number of dives before it was tossed and replaced.
At such high pressures (400 atm), latent signs of stress and hidden microcracks had likely begun occurring. This happens to other high-strength but frequently-stressed items we use like bike helmets, kevlar vests, shin guards, roof, tires, etc.
If the sub worked safely that many times, then the technology was not flawed per se. Deep water pressure didn't just magically increase overnight. The sub's number of dives just needed to be limited. Everything engineered by humans lasts only so long.
So for the quarter million dollars they charged each passenger and their one million in build cost, the sub would theoretically have paid for itself after four passengers or a single full-cabin dive.
I think his plan was not for the hull to keep up for as many dives as an all metal hull, in fact he had already scrapped one hull that showed signs of cyclic damage. His plan was to detect the early signs of damage well in advance with the acoustic detector he had patented and had installed on the Titan. Maybe it was a combination of the hull not holding up as well as he thought plus the detector not detecting as much as it should.
@@sigkilyeah that’s probably the real issue here, he was beta testing the warning system but also putting all his faith in it
The glue, the glue.
@@sigkilFollowing Rush's logic, airlines should skip the 100 hourly inspections and instead install detectors which will let you know in-flight when your wings are about to fall off.
@@qarnos09:42:12 [SUB]: trying to run diagnostics. ascending now. but very slow. sounds have subsided. global RTM alert active all red.
It is called UT Flaw. Used to detect porosity/hole/void inside casted metal product or weld join of 2 metal plates
Carbon fibre reminds me of when auto manufacturers went from glass headlights to plastic to 'save weight' when we all know it was to save money.
Your point?
@@DontWatchProductions carbon fibre is overated
They don't absolutely know it was the carbon.. It could have been the window that was not rated for the depth that failed before the carbon.
Even if not specifically the carbon it’s probably either the interface of the titanium and carbon fiber or the porthole. The different materials strain and deform at independent rates. The design was flawed from the beginning.
@@strechinpick My point is the video claims it was the carbon fiber and this is before any formal investigation.
The ceo said the window moves 3/4 inch inward under pressure
If the window failed before the carbon fibre, then the carbon fibre cylinder would have likely remained in one piece since the pressure inside the sub would then be about the same as outside.
I wondered about that, too. I assumed that she meant that not necessarily was the hull the cause or the thing that went first as opposed to the port hole but that at some point in the implosion at least, the hull did give way/tear apart/fail. But yes, I would have found a different way to phrase that altogether.
The "latest, greatest space-age material" doesn't mean it's appropriate for extreme high pressure applications. This guy is a salesman first and foremost.
As someone who uses structural adhesive to bond CF and Titanium together I'm left wondering if they primed the Titanium. Without a primer there's very little durability or strength in the bond.
Carbon fiber works well for dream liner , because it has a pressurised cabin. More pressure inside , less pressure outside. In case of Titan the situation was reverse ; less pressure inside , more pressure outside.
And really not much pressure inside for an aircraft, just 14-15 psi, not 6000 psi like all of that water pressing on the Titan.
Yeah but u can make the hull segments concave to make outside be inside
Nice reporting , fascinating
Aerospace applications: tensile strength, carbon fiber
Deep Ocean applications: compressive strength, not carbon fiber
anyone working on a submarine should have these basic concepts understood.
Bangs they said was the pressure of the hull. So the hull would adjust and possibly weaken creating new stress points. Stockton said, when things fail, thats when it gets interesting.
I use composit softball bats. And they crack or break. Especially in cold weather.
Also in aerospace carbon fiber is generally either used to contain internal pressure or not as a pressure vessel at all
Does anyone know how you autoclave a 5 inch thick section of carbon fiber?
How long of a vacuum period does it need to evacuate air voids?
I’ll add are 5 inch thick carbon fiber parts a thing?
Cranes and boom pumps get x-rayed to work on commercial sites
On second thought...the Titan collapsed at 13,000', after several trips to the bottom (and back up).... that's actually a very good record for what was essentially a backyard build.
I'm not an engineer or anything, and certainly there could've been a bit more safety research on it, but it seems to me that carbon fiber may have some potential uses for underwater stuff. Like fixed structures, underwater domes, etc.
Unfortunately I think Stockton Rush was using those prior dives as "proof" that his sub could continue to dive. But even he (and passengers) heard cracking noises, and he knew those noises were carbon fibers breaking. He should have known his sub was really a ticking time bomb with a limited life. It was as if he was trying to squeeze out just a few more dives. Was the guy in debt or something?
NDT would've revealed nothing, because the carbon fiber itself wasn't the least bit defective. What was defective was using it in a compressive application, rather than the tensile applications it excels at.
No one seems to be talking about the vessel having a titanium ring GLUED to the Carbon Fiber Hull. When is Glue sufficient to withstand deep sea pressures? Anyone? You cannot tell me Glue was not the weakest link!
This "specialist" seems to not understand the main cause of the Titan accident - the fact that carbon fibers are good at tension but not at compression.
Why not have an aluminum backed carbon fiber? Like a liner to protect the actual carbon fiber. Or steel or something. The other material won't be for the strength. No gap between it. Just to protect against scratches and gouges.
The other material will be the outside liner.
Remarkable that the hull failed at (according to the reporter) 13,000 feet, a full 500 feet deeper than the ocean depth at that point. Did the sub have a digging feature or is the reporting here just utter garbage.
Thing that surprised me is that the acrylic window wasnt much thicker than the carbon hull. 7" vs 5".
20'000 for a stress test. That's nothing to billionaires. That's just stubbornness and denial by Stockton Rush/Oceangate.
Oceangate really could have been at the cutting edge of innovation if they tested it all properly and without tourists until they were sure, but I don't think the sub would have done well in tests. I have this horrible idea he didn't want it testing for this reason. It was all about the money and fame.
People who do things and take risks without taking into account the safety and welfare of others often fall apart in the end. The bigger they are the harder they fall.
Well I hope this will be the last carbon fiber submarine for the moment …
A scratch could cause it to fail? Well they had screwed into the hull to mount computer monitors lol
Carbon fiber has a high tensile strength it just doesn’t have a very good compression strength
Vacuum of space versus Titanic depth is 400 times ratio
Fibers work in tension not compression. Basically the Epoxy adhesive is doing the job.
2 same pressure vessels on earth at 14.7 psi inside. One is going to Pluto and seems a mighty 14.7 psi pressure with the vacuum of space. The 2nd vessel is only going to see the Titanic so has 395 times the pressure since it is 5800 psi there.
The Titanic pressure vessel is using epoxy to hold the 5800 psi outside and the carbon fiber is just marketing hype. Ie giant red flag that none of that fiber is really in tension. Maybe some pretension but still hokey stuff
So it’s impressive epoxy then
$20,000 is not very cost effective for someone running their operation using a $20 knockoff video game controller. 🙄
You completely missed the most relevant point that fiber composites excel in tension, not compression; that its use in this way is fundamentally unsound. Mark Shinnick
Wound layers of fibres will be under shearing forces just from variations in ambient temperature - although carbon fibre has a low coefficient of thermal expansion it's not zero, outer layers have a larger circumference and thus a greater length of material per winding than inner layers, and are thus subject to more expansion and contraction for a given change in temperature than the inner layers. Even without the stresses of repeated deep-dives the previous year, if the sub wasn't stored in temperature-controlled conditions then it was probably weakening with each passing day regardless.
Hello everyone I’m going to ask a very silly question, I’m very curious about science but I can’t understand most of it. My question Is the following, why didn’t they cover the carbon fiber with another material like plastic do that way the water won’t get inside and laminate the carbon fiber??
problem is that the ocean is NOT aerospace. the pressures are reversed and carbon is not the best choice.
I like how his question @ 1:16 was so stupid they just cut him off half way through asking
Carbon fiber is the tensile component of a composite. External pressure places it into compression and the epoxy into tension. This sub never went down more than a few hundred feet.
Carbon fiber composite hull is better suited for pressure from the inside (like the hull of the Boeing 787) than enormous outside pressure (like the hull of the Titan submersible).
Not even considering the enormous force that the two hemispheres at both sides of the hull put on the carbon fiber structure.
Reports state the implosion happened within a fraction of a second. That's not to say the crew didn't hear the terrifying sound of the carbon fibre hull cracking prior to it (as was reportedly heard by other crews on other missions).
One ballast was missing from the sub when found so they knew something was wrong and were attempting to re-surface.
or else when the implosion occured the ballast just detached. also there was no way even if all the ballast dropped for them to get to the surface so fast. the support ship would have heard the implosion hence why they delayed eight hours. they had to change their pants and start shredding documents
@toomanyaccounts latest reports are, there's no way the mother ship didn't hear the implosion. It was equivalent to a major TNT explosion. Lots of cover-up going on. We might have the final truth a year or two from now once public emotions have died down.
your average engineer lol,theres a big difference between space and under the sea,using composite material was just a matter of when not if.
A tourist sub going a few hundred feet under water could absolutely be built out of 5 inch thick carbon fiber. Like 300 feet to see pretty coral reefs.
Well, thanks to Rush for demonstrating the limitations of carbon fiber.
The great difference between aerospace application and the Titan submersible application is pressure. In space the maximum pressure difference with reference to sea level is 14.7 psi. That's it. In deep submergence activities the pressure differential increases by 14.7 psi every 33 feet of descent. The Titanic is at 12,500 feet below the surface. That amounts to 5568.18 psi, pounds per square inch when a vessel is 12,500 feet below the surface of the water. Now multiply that value by the overall surface area in square inches of the composite shell of Titan and you come up with an astounding amount of pressure. Carbon fiber is a non-homogenous material. It's components will flex at varying rates according to how pressure and stress are applied. Steel and titanium are homogenous, all one material. It all reacts the same.
Kills me how the engineers wont just flat out say it was a misapplication of material
This literally translates the phrase "the strongest chain rely on its weakest link"
Stockcon would have had said, *but it's not innovative to test it for safety*
FACE PALM SO HARD.....
What would we expect from someone with contempt for "50 year old white guys" regardless of their knowledge, experience and accumulated skills? It was a 50 something year old white guy who landed an Airbus on the Hudson River with zero loss of life.
Great Segment, Thank You.
That's just great. So they build aircraft from this material than when it fails, shatters?
Was manufactured with a different process and had no lacing/weaving for the Titan submersible
first off carbon fiber is 5 times stronger and lighter than steel. however carbon fiber is only strong like that under tension, not compression like in the titan sub.
2nd that 2 story oven is called an autoclave. autoclave is used to add heat and pressure to the part while the part cures, this removes air bubbles trapped in the resin
Note, he was showing carbon fibre woven sheet ..not yarn wound in a single direction which was the ridiculous way that sub was built. Even toilet roll tubes are spiral wound!
I dont understand why this whole submarine thing is going so viral on the internet to this extent, it almost seems like a manufactured scenario being pushed out onto society for whatever reason 😂
Wasn’t Rush saying they couldn’t do ultrasound checks on the carbon fibre hull. 🤦🏽
That engineer did not mention that carbon fiber composites are strong under tension but weak under compression. The submersible was under compression. Carbon fiber was a very bad choice for the deep sea dive application.
Carbon fiber is only very strong in tension. Pressure from outside the sub's hull put the fibers in compression. CF was nothing more than a filler for the epoxy resin which had some strength due to being five inches thick. The sub imploded because the fibers were asked to be strong in compression. The sub would have easily contained the pressure at that depth only if the pressure was on the inside of the hull. A solid fuel rocket motor with a carbon fiber casing contains the pressure because the CF is stressed in tension. It is the difference between pulling on a string and pushing a string.
Those questions were raised a long time ago by experts. Stockton Rush dismissed them. This failure is not surprising at all.
They apparently only got 3/4 of the way down before they got warnings and cracking sounds, and dropped their "ballast" weights and steel frame and tried to go upwards. But about 20 minutes later the craft imploded. That is the latest info I have fwiw.
Did someone sign their name with a knife on the Flintstone sub
Didn't Stockton Rush screw his monitors to the inside of the carbon hull with screws. I saw that and I thought that couldn't be healthy.
I'm sure there'll be a report on the cause sooner or later
Carbon fiber works better in tension vs compression. In an aircraft, weight is a huge enemy and the plane is internally pressurized though not by much. The titan sub was under immense compression.
Carbon fiber cloth bound with resin. Interestingly I read that the right kind of resin one should use to lay up carbon fiber is epoxy resin. I make split cane fly rods (bamboo) and glue up the sections with two part epoxy resin. The resin is very strong but movement of the bamboo under stress, such as casting or a fish, puts shear stress on the bamboo. Epoxy also needs the correct temperature to cure properly. Split cane rods are usually cured in a heat treating oven. In essense the glue can be stronger than the bamboo, but I don't think I'd trust it 12,500 feet below the ocean with repeated stress in a submersible.
You are correct about epoxy resin. At very low temps, it is extremely brittle. The thickness of epoxy (at each Bond Layer of CF) would be measured in micrometers. Epoxy Bond (at that bond thickness) and at 4 degrees C, would quickly develop stress cracking from the natural flex of the Cylinder under great pressures, and then returned to atmospheric. This is how I believe the disaster happened. CF composite became weaker upon each dive. It had to be the reason. Those 5 persons still weighed their true weights, inside that Capsule. The downward force (weight of 5 people) would have also placed an uneven stress on the internals of the formed CF Capsule, giving the cylinder tendency to take on a slight elliptical. Not certain if payload was factored-in during design, or how the flat floor was secured to the Cylinder. RIP to those pioneers who won't be forgotten.
@@peterduxbury927 Added to that, the carbon fibre was rolled on circumferentially, whereas best practice is to lay up alternate layers diagonally so that the material is equally strong in all directions. Further, the construction was carried out in a large, probably dirty and dusty workshop and there were no processes for degassing the resin, so the layup undoubtedly included dust and dirt and air bubbles, all locations where failure cracks would start to build up.
@@Smannellites I have to agree with you that when laying the CF material, it wasn't cut (or wound) on the bias, but wound circumferentially, with yarns laying upon yarns, with air bubbles locked-into the whole formation. Clearly, an inherent longitudinal weakness in its' design. I also observed the methods of cleaning the titanium annular ring (for the bond between the CF and titanium). A wipe around the ring with (what looked like) an old cloth with possibly contaminants! I also observed that the depth of bond between the titanium end-cap and CF Tube was nothing more than 50mm! Even Stockton Rush commented about this. It is good that many engineers can come together, pass comments, even though we (personally) have no hope of ever building something so unique, it CAN pass all Safety Testing with flying colors! Without Carbon Fiber as a structural element! But (to me) there were many errors that led to this tragedy. I believe that the distant future will provide us with vessels that can reach those 4km depths, carrying paying passengers too, and not just around the Titanic.
Didn't the manufacturer say it was for one time use only
I'm not an engineer, but I understand fibers perform well in tensile, not in compression. An airframe has to take expanding pressure from inside in tensile at less than one atmosphere. The Titan Imploder had to take a ridiculous amount of pressure in compression.
The basic problem comes down that they used tourist trips to the depths to pay the costs of research in the depths. Research in the depths is far better carried out by ROVs. ROVs needn't be built to accommodate humans and human lives aren't threatened. There needs to be another funding mechanism for people who have a lot of money to be able to participate in deeps research using ROVs and maybe bringing stuff up for their collections that going down themselves.
The Millenium Tower owners failed to do a proper geotechnical inspection, the Titan owner avoided NDT. Both pay the price.
Watching the video of the spooler wind the fuselage on that OceanGate vehicle gave me the 'willys'.
It was wrapping in one continuous motion, which is NOT how that should be done for maximum distribution of forces.
It is typically done in an 'X' pattern to support the previous lay up.
Wait, did they actually not do NDE on the vessel? That is wildly negligent if true.
Nope they did not, also Rush said to one of his customers that the carbon weave was obtained cheaply through Boeing due to i being out of date and could no longer be used for aviation. The hatch hemisphere has 18 bolts but they only ever used 17 due to one of them being a pain to access. Also the titanium rings that support the hemispheres were epoxied to the hull, two different materials that expand and contract at different rates. How rush described the hull cracking sounds of previous dives proves that he does not have sufficient knowledge of how carbon fibre behaves. Every time he heard those cracks at different depths weakened then hull every time on top of the usual stress fatigue. Rush dismissed these cracking noises as the the hull just “settling in” as voids in the lay up filled in and weak fibres got torn. One engineer that worked for Ocean Gate tried to raise these problems and was fired from his position. Another previous engineer also said that due to the characteristics of carbon fibre the hull monitoring system would be useless in an emergency and could never allow sufficient time to surface the sub. There are many other construction factors too.
@@Just_Another_Viewer This is going to show up in a lot of engineering ethics material I'm sure. Hopefully, at the very least, this makes a lot of engineers to check their own due diligence.
Both reporters must understand. If they were there... Both of you become Hershey's Cookies and Cream....for Crab's.
Using carbon fiber like in an airplane is not dangerous because of an open space while using it underwater and submerge it as deep as you can will pose a problem because water is not an open space. The pressure it will give are very tremendous.
theres a YUGE difference between aerospace composites and deep sea composites.. even outer space is only 1 atmosphere or 1 bar difference than earth..
every 30 ft is an extra atmosphere or extra bar of pressure under water.. thats 1000 bars down near the titanic.. insanity
The greatest irony is, that Titanic itself sunk mainly because people's pride and overconfidence came before reason, knowledge and facts. Like Titanic, the worst case scenario was mainly ignored, because it was identified as an obstacle for business and public image of the vessel, the company and the brand. Like Titanic, most of the people that died were invited or payed for the travel. Unlike Titanic's demise, that took hours, Titan was destroyed instantly. Makes you wonder, if all these people that went down there, really cared about the tragedy and what caused it, rather then just being curious adventurers that wanted to do something only very few get the chance to.
Carbon fibre and fibre glass have both been used in boats.
They both deteriorate over time. It seem likely that if you use these materials under far grater stresses that they will fail a lot faster.