Composite Materials: Practical Design Limits
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- เผยแพร่เมื่อ 4 พ.ค. 2024
- Theoretically, composites promise strength several thousand times greater than steel. So why don’t we have composite materials everywhere? The practical design of composites severly limits their capabilities. Once you understand the practical limits, it provides a useful design guide for how to apply composites and maximize their advantages.
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References
[1] E. J. Barbero, Introduction to Composite Materials Design, 2nd Ed., Boca Raton, FL: CRC Press, 2011.
[2] R. A. F. J R Calvert, An Engineering Data Book, Southampton, UK: Palgrave, 1999.
[3] W. Author, "Example of a Composite Material," Wikimedia Commons, 25 Jan 2009. [Online]. Available: commons.wikimedia.org/wiki/Fi.... [Accessed 27 Nov 2020].
[4] M. Gopalakrishnan, S. Muthu, R. Subramanian, R. Santhanakrishnan and L. Karthigeyan, "Tensile Properties Study of E-Glass/Epoxy Laminate and pi/4 Quasi-Isotropic E-glass/Epoxy Laminate," Polymers & Polymer Composites, vol. 24, no. 6, pp. 429 - 446, 2016.
[5] DNV-GL, "Materials," in Rules for Classification: Yachts, Houston, TX, DNV-GL, October 2016, pp. Part 3, Chapter 5, Section 2.
[6] C. Kothlow, "How Rule of Mixtures is Killing Your Composite Design," Siemens, 7 May 2020. [Online]. Available: blogs.sw.siemens.com/simcente.... [Accessed 30 Nov 2020].
[7] M. Manske, "Generic Stress-Strain Graph for a Ductile Material," Wikimedia Commons, 13 May 2008. [Online]. Available: commons.wikimedia.org/wiki/Fi.... [Accessed 27 Nov 2020].
[8] American Bureau of Shipping, "Materials for Hull Construction - Fiber Reinforced Plastic (FRP)," in Guide for Building and Classing Yachts, Houston, TX, American Bureau of Shipping, July 2020, pp. Part 2, Chapter 6, Sect. 1.
[9] Shenoi, "Composite Mechanics - Introduction," in Course Notes: Structural Integrity, Southampton, UK, School of Engineering Sciences, University of Southampton, 2008. - วิทยาศาสตร์และเทคโนโลยี
I think that was supposed to be 2300% (not 230%) for fiber/steel.
Whoops. Yes, you are correct. The ratio of fiber / steel tensile strength should be 2300%, not 230%. Despite my best efforts, a typo slips through every once in a while.
@@DatawaveMarineSolutions If we're talking about 3:20 in, then I think the root typo was an extra zero in the Tensile Strength of Fiber. Maybe using the wrong units, as N/mm^2 is closer to the number listed. Though I found another site suggesting that the original number is roughly correct, and I'm not in a position to tell which source is mistaken.
@@DatawaveMarineSolutions Put a little text pop up over it/near it for future viewers. I was going to say the same thing.
coming from an aviation background: prity good general lecture! would like to see one going into long life of composites: Repair issues, ability to flex, difficulty to find defects (resulting in a structure that visibly looks good to the user but fails under NDT), production difficulty, UV issues, fastening issues, corrosion etc.
That would be cool
Thank you, you answered a question I was actually pondering over
Another GREAT video: very clear and useful to give an initial understanding of composites in naval engineering. And I think the generalization used here is a wise decision to allow a more comprehensive vision of such a complex subject. Congrats. Liked it a lot ! :D
Thanks again for making these awesome videos!
I would also imagine that maintetance of these materials would be harder than when using steel. With steel, if a container rams a hole into the top of your double-bottom tank, you remove the jagged edges and weld a piece in. Doing that with fiberglas would be probably much different (and harder). And, the bane of innovation, no port would have the material at hand, so fixing the issue would be a logistic problem too.
Hello. Could you do some kind of analyze video for the Rafnar's ÖK hull shape? It looks very interesting and i would like to hear your opinion about it.
I imagine the small production numbers of individual ship classes are a further hindrance to the adoption of composites.
It is just not enough, to design with composites, but rather for composites.
Which unfortunately balloons the costs, if you can't distribute that over thousands of sales.
Correct. This is also why the yacht industry largely builds with composites. For example, I believe Bavaria is the largest production yacht manufacturer in the world currently (I have not seen the latest sales figures). And that is the perfect example of a situation where composites are economical. Bavaria can design a single class of ship, optimize for that design, and then optimize their manufacturing to streamline the process.
Incidentally, this is also why new yacht models are rare. It requires a very high tooling cost to setup production for a new hull shape.
I feel like I just became more understanding of the hairline cracks in my 30 years old fiberglass day cruiser. Thanks for a good video Nick!
Hugo Boss cracked at the Vendee Globe 😳
How did you manage to repair a broken composite hull with the same safety margin compared to a steel one ? I just think of repairing a basic kayak 50 years ago... Steel and other traditional materials seems to me to be safer ! Thank you for the video.
Cost of the resins, particularly epoxy, is enormous too.
so safety factors of x12 to x15 for composite structures? ...good thing it's light....and good thing we have access to good core materials also.
Interesting. Guess this is why racing craft are way ahead in using these materials. And why IMOCA yachts are fragile in some cases.
Worries me about the now widespread use in airliners. But I guess their stress limits are much lower compared to ships.
Funny thing you mentioned the airliners. I lived in Seattle for a time and took the factory tour to learn about the Boeing 787, which has a composite fuselage among other parts. Just from the way they fabricated it, I can tell you that they are a step above my typical level of engineering. They have a much deeper understanding of composites than the boating industry.
I can't confirm this, but I did hear a rumor about Boeing and their use of composites. We had the math and material science for basic composites back in the 1970's. But it took decades before Boeing was willing to use composites because they needed to generate data and perform further research on the fatigue of composites. The airplane fuselage endures a lot of fatigue loading, which is how materials fail after 20 - 30 years of use. But no one could predict the point of fatigue failure for composites. That was the secret sauce that Boeing cracked. I still want to look into that further and see how much of their findings were made public.
@@DatawaveMarineSolutions I hope they got it right
How does aluminium hull elasticity and plasticity compare to that of steel hulls? If I wanted the most durable hull possible, would it be advisable to 'not' use aluminium even though I might save weight?
I don't think there is one absolute winner for materials when choosing "durable". Each material has weaknesses in different failure modes. But in general, I would likely pick steel. It has a higher yield stress than aluminum, and it includes a wide plastic range between yield and final failure. Most importantly, it can be easier to find qualified welders for steel than for aluminum.
@@DatawaveMarineSolutions A thousand thank yous for the response.
@@DatawaveMarineSolutions In a hypothetical situation, would Titanium be a good material for a ship hull.
I say hypothetical because I know Titanium is very expensive and difficult to fabricate and weld. But if the US Navy with its bottomless budgets wanted to make a small Corvette using a Titanium hull, how would it work as an overall material in terms of strength and coercion?
@@thepessimistictitan2655 I can't say exactly, since I never had the chance to work with titanium. But I do know the Typhoon Class submarines from the USSR were titanium alloy (I would guess just the pressure hull). So it clearly has some advantages.
Thank you Nick. Soon you'll be able to grow your own composites with self-organising compounds, much the way a crystal 'grows' in nature. Great video and Fair Winds to you..
Sweden and Danish naval architects/engineers are almost 40 years ahead! here is a link to Royal Swedish Navy "Visby class" corvette, the class where designed in the late 90s. After delays, the first "Visby" enter service in 2009. The same Swedish naval architects had 15 years earlier worked with the Royal Danish Navy and naval architects on the first full hull composite build fast Standart Flex 300 type multirole ship/Patrol vessels(multi-purpose, modular weapon system as engines too), know as the "Flyvefisken" class. At the time they were the maximum length a carbon/composite vessel could be built. Resin is control in a controlled environment -know as an own ;-), as strength goes the biggest issue is micro air bubbles in the resin! this issue where address in the "Flyvefisken" second batch -or "Mark 2" from1992 by using a vacuum, making the hull on top of the mold, and suck the resin true the carbon layers. The Swedish naval architects had pioneer composites constructed vessels and were therefore contacted by the Royal Danish navy in the early 80s as partners, so the "Visby" class benefits from the experiences learned from the 80s in this partnership. th-cam.com/video/H9RdcmICyuQ/w-d-xo.html
The Ocean gate submersible just wound their CRFP around a mould which might have contributed to its failure.
Interessting overview about composit structures, all the downsides that are listed, most likely to represent reference to glass, and to level of design/enginerring , and at last degree the method/capacity of manafuctruing parts ( process, tooling rigging/handling and cost).
IF we talk about problems on materials with wicker spots on diferent material, for example welding, thats why you due inspections & x-rays to them.
If we refer to quality built composites they will deliver the promisse but at higher prices, there are not "only" good conditions, or you have or not , elese is scrap parts or poor design
i find very "off" to compare the "promisse" to "real", the sample to qualify composite material have in consideration how the are built (%resin, fiberplacement, delaminations, voids..), etc.
Composite material have good properties if their are handled properly (according with their manufcturing process) as any other material.
Under the test X with X properties the strenght is X, so its the reference. Can't expect to use the same amout of fiber and resin of the qualification, and thats it. Rarely seen clean rooms, ply cutters, layup tooling, vaccum tools or cure system. So then appear the worst condition, and people seam to be satisfied.
For calculus the contribution of resin is never accounted as it doesnt contributes and the fiber /plies need to comply with maximum deviation with their orientation as well other safety factors(reducing their max strenght).
Honestly i disagree because with proper mafcturing (that is expensive), quality control and design, i those are great.
apart ofour different views,
Thank you for your videos, its great to see people sharing their knownledge & experience
And a little info on the former Royal Danish Navy's "Flyvefisken": en.wikipedia.org/wiki/Flyvefisken-class_patrol_vessel
Can you please quantify the term strength as your use of the term seems to be to mislead The same with the term composite Composite is a material which is produced from two or more constituent materials. The steel used is ship construction s technically a composite. Quantifying your position is critical. Fibre-reinforced polymer (plastic) like steel is not a generic composite, Almost all of your arguments against FRP can also be applied honestly to metal Both are dependent on orientation thickness and composite attributes By using eg Carbon E-glass S-glass aramids etc, then there is the polymer it is encased in modifies and negates the argument. As this is the same for steals do they include for example carbon alloys silicates etc then there is the crystalline structure orientation etc. The thickness and how it is combined is also a factor like it is with FRP. With FRP a core is used as is a web is with most meatal to deflect/resist loads. This aligns with your final inference that the manufacturing control of the laminate integrity, this is mitigated in many ways. As with metal testing is key to checking and specifying the properties of the product throughout the process by testing eg weight, accounting of quantity and visual inspection, etc Then there is mechanical testing and x-raying etc. The testing of all materials have the same outcome you will always take the lowest denominator and apply it to the approved safety factor. Every product needs to be correctly engineered and specified with the appropriate safety factor. The engineer when spec-ing FRP like metal must mitigate material inconsistency with the specific specification, in metal plate by specifying alloy content and combinations etc( 41xx steel) with FRP they will specify a filament arrangement percentage to a polymer percentage. They may instead specify an engineered prepregs location and orientation to achieve greater control over the outcome. They may similar to a steel web weld specify the core (web), polyemer bonding agent.
In conclusion, FRP has no limitation in relation to any other correctly engineered and managed material. The true reason that it is not so widespread is more to do with the cost, eg the complexity of construction. and economy of scale. This is another complex story. I do believe in the future that FRP will become far more commonplace in modular supper structures. If modular they can be reused over and over after a hull reaches its used by date As it will save on maintenance and reduced VOG's and displacement mass Things like prop shafts as the economy will outweigh costs. The same with Propeller blades as large scale Cabon fibre FRP 3D printing is not far away and the benefits will be huge. Again another story for another time. Sorry, that got away from me, I was only going to referance the first few sentences.
I did intentionally use a generic term for strength. But I do add some subtle details to try and address the more technical aspect. For example, at 2:14 the table heading specifies "Tensile Strength" for E-glass fibers. Tensile strength is a specific material strength test and the one most frequently used to characterize the strength of isotropic materials like steel. If I was quantifying strength of a laid-up composite, I would need to specify compressive vs tensile strength and specify the material orientation. But the pure fiber alone does not require the same level of specification.
As someone who has built a number of hand laid Glass Fibre boats from 24 to 29 foot, I would NOT reccomend or use Fibreglass as a boat building material. Ok for a runabout but believe me....Gell coat covers a multitude of sins.... think about it. If you knew how many bubbles/faults/gaps in fibreglass boat building you would not buy one.
"Group all composites together", all that's needed to be heard to realize that the knowledge of composites are very weak. (Btw, I'm a metall guy working in machining of aluminium, steel, nickel-alloys etc and I now darn well I can't treat composites all alike just like all iron based alloys can't.)
You are correct that one cannot treat all composites alike. However, when trying to explain basic physics of composites, I find it more useful to avoid confusing the matter with myriad details.
@@DatawaveMarineSolutions Then you also have to include all alloys as one, from pure aluminium to Inconel via cast iron and Hardox...
With ANY material selection determing application needs and comparing them to the different types and costs for manufacturing is key. Generalize and you fail.
You're very knowledgeable, in contrast your energy level is just not very captivating, I endured due to a vested interest in the tech, but if you want more likes, and more views, you need to zest it up a bit!
2.5x is 150%
You still design vessels made of wood? It’s a natural composite. Imagine luthier standards applied to wood for a boat design…