Yeah, I can’t believe that after researching metals and carbon fiber videos on RU-vid for just a few minutes that ANYONE would be able to come to that conclusion! May they all see Heaven’s Gates.
This explains why Titan was never issued a certification of safety. James Cameron was always right about using titanium and stainless steel to build submersibles.
According to some studies, Carbon Fiber can withstand depths of over 7,000 meters. And it certainly survived several trips to the Titanic so it does work. The problem is that nothing can stand repeated dives, and as yet we haven't developed a good way to non-destructively test when Carbon Fiber has reached its limit. I should also point out that the experts don't seem certain yet the carbon fiber caused the failure. Several people have pointed to the very dodgy porthole, and some say it was the combination of the titanium end caps and the carbon fiber that was the real problem. Maybe it was even something else entirely, since it seems like safety wasn't exactly priority number 1 with Ocean Gate.
@@rodh1404 carbon fiber has ALWAYS been developed and used as a tensile reinforcement. It is common knowledge in composites that fiberglass performs similarly if not better than carbon in compression applications. Once you start pulling on the laminate in tension, carbon out performs justbout everything. I think this hull design just used so much of it (4" thick?) as to just brute force the calculations. But as many others have pointed out, typical composite laminations fail over time due to micro crack in the epoxy marix. tiny cracks occur and grow as the structure is loaded. Add extreme thermal cycling and the dimensional changes from the pressure and its gonna break down. Ive built a bunch of skis and skateboards and random parts from CF and glass, nothing too crazy but even with my basic experiences, i would NEVER pursue a CF sub for deep water. The only reason to do it this way is 1. probably cheaper than the extreme grades of metals required 2 much lighter weight, which means support systems for docking the sub needed to be much smaller and cheaper. also carbon fiber has proved time and time again that it is great at seperating rich people from their money. its a good buzzword.
For the people saying that carbon fiber underperfomed: Remember that the advantage of carbon fiber is not its raw strength, but its strength to weight ratio. Titanium took 3x the force of carbon before it broke, but it also weighed 3x as much. Also keep in mind that these tests were strictly in compression, while carbon unquestionably performs its best in tension.
"Titanium took 3x the force of carbon before it broke, but it also weighed 3x as much" This is true, but also the driving reason for asking why people hype it up so much if it's about the same as titanium in terms of strength to weight. Especially when you take cost into consideration.
@@pcmasterracetechgod5660 Because you can form carbon fiber into virtually any shape without much issue while it would take a lot more to do the same with titanium. Plus the price is pretty much the same. If you are just sticking norm pieces together, titanium would be better. Make it a bit thinner than the carbon tube and you'd have the same effect. If you are going to have more complex forms and a low number of units, carbon fibre becomes more attractive. There is no absolutely perfect material.
The carbon was only 1.5mm thick. If it were the same as the titanium, it would have had a collapse stress of 5000kg-ish. Likewise, if the carbon filaments were wound diagonally, the failure load would have been even higher. This experiment can't be compared to the Titan submersible failure. To do that, the tubes would need to be 2 feet long so that they could buckle rather than undergo ductile compressive collapse, and the load would need to be set at 80% of what would produce single load failure. So that fatigue of the carbon resin would accumulate over each load cycle, making the tube gradually weaker during each cycle.
He was too stubborn to care. I saw a video where he was explaining his cutting corner design with cheap lights, bare minimum instruments and game controller drive. He was saying "as long as the main structure does not fail, everything else can fail, you will be safe". Anyone with common sense would be saying "at 3,800 m depth, NOTHING should fail!"
Naaa, don't think so. Little d!psh!t CEO Crockton CRush would've just said, "Tech has advanced 10-fold in the last 10 months. My carbon fiber, on a scale of 1 to 10, is rated 11."
Note: that carbon fiber tube was likely _stronger_ than Titan's CF because it was woven in multiple directions (though, obviously, much thinner overall than Titan). But what people keep forgetting to mention about Carbon Fiber is the danger of *repeated stress*. It might handle a given level of stress once, twice, etc. but each time adds tiny fractures and eventually it fails *without notice*. That's why carbon fiber bikes need to be X-rayed for microfractures after any significant accident. _none_ of that was done for Titan after each dive.
I did notice that when the carbon fiber gave under the pressure, it frayed rather than shattering like I'd have expected--is that due to it being woven in more than one direction as well?
Unfortunately, people just keep repeating 'carbon fiber bad' without understanding why. It's not necessarily that it's weaker, it's that when it fails it's sudden and absolute.
Thank you for goodness sakes people are so quick to write off carbon because its "experimental" and not tested that material is plenty strong for 1 or 2 dives the deepest dive ever was done using carbon fiber 35k feet in the Marianas Trench and it was done once for a reason no repeated stresses.
One thing to note if you're watching this after the titan accident: notice that the hydraulic press starts applying less force to the material once it starts yielding. A hydrostatic column, in contrast, is not so kind
@@nutinmyass by being mostly made of fluid, which is in practice incompressible. What makes certain animals (and poorly made submersibles) vulnerable to pressure is gas content, which has to drastically change volume if in contact with a dramatically different pressure environment
Carbon performing rather low was to be expected. Because its strength results from the fibers being arranged in the direction of stress and then being pulled. It's like a rope: Strong if you pull on it but doesn't resist any squishing
The main failing point of the material used was actually the resin holding together the beam. Many people be like: “Carbon fiber is stronger than steel! It’s the best material ever, it’s the future…” blah blah blah. What they don’t realize is that only the mere “fiber” is stronger than steel. Common mistake. Even aluminum showed better result… I did expect steel and titanium to outgun it but the aluminum was a surprise. Most people that are into cycling should check this video out before dropping motorcycle money for a carbon toy. XD
@@danielhristov6175 You're missing the key advantage of carbon fiber: it's strong, but *LIGHT.* People don't like it simply because it's "strong", but because it's insanely light for it's strength. If you want pure strength, then sure, use steel. But if you need something that's light, but also rather strong, carbon fiber is an excellent fit.
@@danielhristov6175 Compare the weight to the results and you get why carbon is a valid option. Carbon and Titanium have nearly the same result when weight normalized. It's a lot stronger than aluminium when weight normalized. That is where carbon fibre gains an advantage.
That was actually really cool to watch. Found it very interesting. I mostly applied and imagined the deviation of materials as it would relate to a connecting rod in an internal combustion engine.🧐
Who would of thought this video would pop up 10 months later as a suggested one for me. This press guy hit a home run when he made this and didn't even realize it would take 10 months to really "blow up" 😮
@@pvpdm why wouldn't it work on metal? I would think you would see the temperature change. The metal may show its surface as an even temperature throughout the change, but it would still be visible that the temperature is changing?
i wonder how much is the temperature variations (before compression and just after) of the metallic pipes... maybe would be interesting to measure these parameters.
Well, this isnt really indicative of much. They crush carbon fiber in the direction of the filaments, which is much, much worse than how Titan experienced pressure. However, that doesnt take away from the fact that a carbon fiber based pressure hull is bad for external pressure but superior to any metal for internal pressure. So, if you wanted to build a tank to contain internal pressure, carbon fiber will give you the best result in terms of weight and maximum sustainable pressure. But dont make a sub from it...
Also the carbon fibre layers was 5 inches thick, so probably lasted longer but ultimately either end cap glue failed or porthole or carbon fibre delimitation within layers
@@PebCak42 I'm sure you know more about it than I do. But looking at the way the CF shreds apart here, wouldn't water have an easier time penetrating it? In any event, OceanGate had no business taking people down there anyway. As we saw in the search for them, anything people can do on the ocean floor, ROVs can do better and safer.
@@nancymcmonarch I'm not that deep into carbon, but from what I understand it's not designed for that type of strressor. It performs reasonably well in the areas it's designed for, considering weight-strength ratio. I'm more into metals.... There are a lot of factors when it comes to materials, some just break/rip without any visible warning, some deform before breaking. It's very important to know what kind of stressor the material will experience... compression vs. tension, enduring stress vs. cycling stress, element exposure etcpp, do you need visible warning or do you have other ways to detect potential flaws & failure. E.g. certain parts for high performance engines are x-rayed for potential flaws that can't be detected any other way. It's a science in it's own right. But I agree, they had no business doing what they did, especially in the way they did it.
@@nancymcmonarch That's part of the problem with CF. Once any kind of fracture of the matrix occurs, water can penetrate and start pulling apart the layers, i.e. delamination.
@@hariman7727 Price and weight. But don't forget the cylindrical shape was also a problem. Spheres are strongest under pressure from all sides. Cameron used spheres.
From the safety point of view, my main concern about carbon fiber is how minimum deformation it shows before coming undone. For a vehicle like a submergible, the deformation from the titanium could mean when it starts showing material fatigue after multiple trips, there is a big chance it will be deformed and survive, allowing a post-submerging inspection to identify it's reaching its limits and decommissioning it before a fatal incident, while the carbon fiber looks for a submergible, it won't show any previous deformation until the trip when it suffers catastrophic failure..
If you look at the pipe here the weave of the fibre shows it going in two directions increacing the strength. The sub only had the fibre strands running in one direction so not as strong as it should have been.
I just feel like metal is somewhat one piece so it won't really make a hole unless something punctures but carbon fiber has so many weaves that there's so many possible places for holes. It probably good for something on land like body armor where you don't have water seeping in and it's tough and lighter than steel but I wouldn't trust it going to a really deep depth where everything fails all at once and you don't know what hits you
@@MrLuffy9131 it didnt leak water... it delaminated lost its strength and failed. if it were to have "leaked" it wouldn't have been imploded. the cabin is pressurized with oxygen right so if it were to leak it would be constantly fighting the pressure of the fluids around it. they would notice the pressure instability and surface but it failed almost instantly with no possibility of taking on water.
The titanium (and steel, PVC, aluminum, etc) in this video failed by yield, which is gradual and detectable. Cyclic stress and fatigue causes failure by crack propagation, which can be much more sudden. Titanium is susceptible to fatigue cracking no matter how high the yield strength, so it must be designed with a maximum number of cycles in mind (just as the carbon fiber in the titan should have been). There's no good reason to make a sub out of carbon fiber, but with properly calculated fatigue life, it could have been safe just like titanium. Really though steel would be the better option because it has a fatigue limit, where if each cycle doesn't exceed the limit, the vessel will always be safe. In some cases it may be cheaper to simply say that the vessel should only complete x number of dives, which is acceptable in most materials, but at the end of the day steel is the only material with a real advantage there.
To all the "Scienceticians" observing this anecdote..... The carbon Fibre tube is weakest at the ends. The diameter of the press forces the cylinder BETWEEN the layers of carbon. So, the "failure" you see is the least surprising outcome there could be. Aside from that, CF if an additive material, titanium is a "contiguous" material. If you want the strength of Titanium, simply add more CF. As a test of perspicacity, several of the audience fails.
As a metallurgist and fdy engineer I pulled test bars all the time..the psi ratings depending on the alloys was important. Strength, ductility vs wear and fatigue in operation was crucial. CF has flat strength in stress, but no ductility and fatigues quickly. Test bar pulls gave you the boundaries of useage in desired applications.
@@larrybe2900 Bike frames are made from carbon fiber everyday. The top bar is under significant compression. Wing spars are indeed made with carbon fiber caps separated by a shear web. Carbon wings are quite suitable. The compression strength of titanium is 50% of its tensile strength. The compression strength of stainless steel and aluminum is 40% of its tensile strength. The fact that carbon fiber is weaker in compression is like every other structural material.
This is a great video, showing the sheer folly of the Titans construction! It is criminal that there are engineers that would’ve thought carbon fiber is a good idea for a submarine!
metals fail but still retain "somewhat" of a shape and sub occupants might be crushed or might have small chance to survive. carbon fiber was literally "catastrophic" failure with zero chance of survival after failure of crushing integrity. It shatters instead.
not really, titan is a very poor example of that conclusion. it probably had faulty engineering for where the titanium was married with the carbon fiber hull, faulty method of applying the carbon fiber/production of the hull itself and faulty shape for deep sea diving. just to name a few. it probably had sub par solutions all over it
@@zlonewolf probably `easily` avoidable by making the hull much thicker, so the design could theoretically much deeper(even with this shape). not having a subpar marriage of the titanium and the hull(thinner lip to support it and just glue used). not to mention a pressure chamber shaped like sphere instead of a tube. any material could have failed with this design
You could try testing compositions of different materials (like using different tube materials for each layer stacked inside another), would be nice to watch too Keep it up and thanks for the great content
Here is the ranking: (stainless steel held 15800Kg with 58.62g in pipe shape, which means it held 270k times its own mass but isn't the strongest here) 1. Titanium: 9190kg/32.63g= 282k times own mass 2. Carbon fiber: 2998/10.91= 275k 3. Stainless steel: 15800/58.62= 270k 4. Aluminium: 3840/19.76= 194k 5. Acrylic: 1538/8.69= 177k 6. PVC: 1004/11.43= 88k 7. Steel seam pipe: 4750/57.56= 83k 8. Brass: 2568/45.16= 57k
titanium and brass are wrong, they started to deform way before the marked pressure in the video - watch it again Brass started to deform clearly around 1900-2000kg and Titanium started to bend around 7000 already, while carbon fiber held until 2900.
@@blinzi69 What's being measured is the max pressure it can withstand before catastrophic failure. Deformation obviously isn't good but it's not up to the level of catastrophic.
This is absolute insanity, I was literally doing this exact experiment at home when I stumbled across your video, and because of your warning I just packed away everything instead.
Granted, it was 40 years ago in a high school Physics class, but the teacher had us go over the properties of each of these materials (except for pvc and carbon fiber) in addition to giving us a multitude of various shapes (squares, triangles, cylinders, rhombuses (rhombi? = ), etc. to choose from to test out our hypotheses of which materials and shapes would perform best in a deep ocean dive, which he had very wisely tied to diving down to the Titanic, although it's exact location hadn't been determined at that time. After much debating and running the numbers among classmates, we all had to agree that the sphere was EASILY the best and safest form. So, this was a HUGE part of the reason why we were so shocked when we first saw the cylindrical shape of the Titan. We immediately knew it had imploded, even before the Navy said they had detected it that Fathers Day with their equipment. Difficult to comprehend how such educated guys could be SO foolish with their own lives!
Carbon fiber is great for most strength applications but not for compression. As you can see in this video, the hydraulic press compromises the fiber one strand layer at a time.
Carbon fiber used as a building material is not the problem. Using it repeatedly without a proper way of testing its integrity after each dive was the problem. Having a submarine with so many glitchy, twitchy, defective safety mechanisms and systems in general was also a problem.
Would be amazing if you could build a strong water chamber for the press to push pressure into. My understanding is that old steel foundries are used for this purpose at depth testing research facilities. Being water exerts pressure equally around instead of just the ends, the results could be interesting. I'm willing to bet the investigation on the Titan will do such tests at these facilities with mockups based on the production methods of the sub's pressure hull. Really nice tyo see stainless so strong. Which stainless ASTM grade was that? 304? 316?
For those wondering about the *lack of shattering* of carbon fiber, there are 2 possibilities. 1. The height to thickness ratio of the sample was such that buckling (catastrophic failure) would not occur. Criteria based on geometry and material properties will determine if buckling or crushing.will occur. With a longer tube you will see buckling. Thanks to @josephgarrett for pointing this out. 2. Regardless of 1. the nature of a simple hydraulic press will ensure a constant velocity of the head. Otherwise known as constant displacement rate. The hydraulic fluid is pumped into the cylinder at a constant rate meaning constant downward motion after yeilding (failure point). After yeild you can see in the video that the force begins to drop, yet the downward speed is constant. So you can compress the sample by the same amount, but with less and less force. More advanced machines can control displacement and force with software but this test is incapable of applying a constant force to the tube. If there is anything I missed please let me know!
I don't believe this is correct....... the reason there is not catastrophic failure (with any of the specimens) is because someone did their homework and solved for the necessary geometry/stiffness to induce crushing under compression rather than buckling (for example the J.B Johnson/Euler interaction curve).
Agreed, the test is completely unrepresentative on how these materials would behave with uniform external pressure as experienced at extreme depth. To be fair to the makers of the video; it was not intended to be.
fascinating! that makes a lot of sense, thank you for this comment. I guess engineers generally design structures so that any deformation is a failure, catastrophic buckling or not, staying within the safety margin established by a test like this.
Wrote too much for a simple concept: all kinds of fibers resist traction, not compression. Simple this way! On any pressure vessels made of any fiber, when the inner pressure is bigger than the outside pressure the fiber is under traction, but when the outside pressure is bigger than the inner pressure the fiber is under compression!
Carbon Fiber did better than I expected but still just doesn't handle external compression nearly as well as any of the metals usually used for pressure vessels. Stainless did way better than I expected.
If you saw a serious testing of acrylic it will shock you for sure, the testing on this video is done by a non professionnal, acrylic is used in field where he outperforms even stainless steel.
I see a few notes about the carbon pipe, and it's also worth keeping in mind that carbon fiber materials are engineered to be strong when put under certain directional forces. The person designing a pipe wouldn't expect it to be compressed along its length, but instead pushed outwards towards its sides. So this is essentially the toughest thing you could do to this pipe.
Pull strength it will behave another way yes also directions of the strands shows the structure of the force must be applied by the way carbon material used is not advanced one just lining
An extremely important factor about Carbon fiber that was not included in this video (though isn't important here) is repeated/cumulative pressure cycles weakens carbon fiber, so it needs to be downgraded after each pressure cycle until it is retired permanently from further use. I know this being in the rocket business where CF helium tanks were rated for 10 full pressure excursions from zero/ambient pressure to 10000 psig and back to zero. 10X was it, the tanks end up in the scrap heap forever being retired from future service. Usually, holes drilled in them so they cannot accidently be reused.
Who gives a Sht! about rich tards that want to see ship wreck?! Everyday innocent ppl and children die all over the 3rd part countries and you don't whine...
Thanks for the table summary. I was just thinking of doing the same and then saw yours. It's interesting that titanium, carbon, and stainless all have the roughly the same compressionc strength(under a cylendar form) per weigh.
Awesome! Another important factor that could be use to sum up in the ratio is the cost. This is one of the reasons SpaceX choosed Stainless Steel instead of Carbon Fiber at the Starship and Booster
Yes. He does have a video with titanium and CF plates, doing bending tests. Not cylinders pressed from the side, but still interesting. I'm going to watch it now. [correction:] The video shows bars from various materials (not "plates").
It wouldn't matter as this also would be unrepresentative of the uniform external pressure experienced by a sealed container at extreme depth. To do this you would need to make a sealed vessel, place it in a pressure chamber filled with water and then increase the pressure of the water.
_I'm bulletproof, nothing to lose_ _Fire away, fire away_ _Ricochet, you take your aim_ _Fire away, fire away_ _You shoot me down,_ _but I won't fall_ _I am titanium_
The CF on the Titan was actually weaker than the one in this video. CF tubes are stronger at taking compression when vertical than horizontal. Titan was doomed to fail.
@@forbidden-cyrillic-handle Yeah they do. RUssians do it all the time but guess what. most titanium comes from Russia. Anyways the best thing ocean gate could've done is to just use a steel pipe and add more bouyancy
Great experiment that answered many questions in my mind. Carbon fibre is not even as strong as aluminum but its major advantage is light weight. Also, it proved that steel as one of the oldest human discoveries is still the king of compounds when it comes to strength. Thanks for video.
you wrote "Carbon fibre is not even as strong as aluminum" but aluminum has a strength of about 500 kilonewtons compared to carbon fiber which can have up to 1600 kilonewtons of strength
@@commendatore2516 beause people dont understand how cf works. In this case where hes basically pressing the fibers downwards the main force taker is the resin. However the resin only is an addition to fixate the fibers in position. The fibers should take the load, which they do best in tension directed to the fibers. Pointless comparison like this. And as you said, aluminium is not stronger than cf. It just so happens that aluminium is isotropic (takes forces the same no matter which direction) and cf is anisotropic (force taken depends on direction). A well built carbon part will outperform aluminium anyday. Yet, depending on application obviously, maybe not for a sub, but definetly for any other "normal" application like car parts etc.
A high strength to weight ratio only makes sense in airplane design, but for a sub, absolute strength would be the more important feature, I'd think. Excess weight can always be countered with added buoyancy.
The Trieste used a tank of gasoline for negative buoyancy. That's what I would do as well. The tank doesn't require a large wall thickness because gasoline weighs about 6 pounds per gallon and is not compressible but salt water weighs about 8 pounds per gallon thus you have 2 pounds of negative buoyancy for every gallon of displacement.
Don't forget Stockton Rush was an aviation engineer. He could be possessed by these "high tech" materials and consider "traditional" materials inferior, old school, not innovating enough.
It's incredible the quantity of good engineering videos that were floating somewhere in the web, and are becoming famaous right now with the submergible story!
Stainless steel has the highest force per area (psi), while titanium has the highest force per weight ratio. So, if you want strength and you don't care about weight, choose stainless steel, and if you want the least weight that can shoulder the most force, choose titanium.
