Uhhh, that’s a real knee-slapper

@@sunshinemagicalrainbowunic4004 failed fast for Stockton 2 and half miles down.

@@liamhickey359 you must ask why when it had in 20-21 just been repaired or replaced. And many dives stated were prior to this remake. Was stated only 1 dive per year thereafter as many cancelled. So possible 1 dive or at most 2 prior to this here dated tragic one! Hull failure so quickly, not as before years? What else happened other than that?

@@maryannsinopoli1751 wouldn't mind going on a date with you.

Thanks for the feedback

yes i recall the video where he spoke of this in general after its first dive .But According to Stockton this is normal .The noises settle down eventually , he got that right . If we could talk to Stockton now i expect his opinion would change drastically

Those loud pops were the epoxy snapping apart.

Also the fiber would be de-laminating from each other. which would crack the epoxy

@@JoediyLab Its like standing on a pepsi can, it will hold you up until the slightest little touch on the side and it implodes.

@@chuckmiller5763 nice comparison

Thanks I ordered another mic and pop filter

@@JoediyLab Very good idea.

Thanks for your feedback. the video was of an older sup. The Titan was wrapped with prepreg using a tape laying process. But we do not know what the ply orientation was or the cure and compaction process was.

From the CW article linked in Part 1 (FWIW): "... performance parameters: Length, 2,540 mm; outside diameter, 1,676 mm; service pressure, 6,600 psi; pressure safety factor, 2.25 ..." "Spencer opted for a layup strategy that combines alternating placement of prepreg carbon fiber/epoxy unidirectional fabrics in the axial direction, with wet winding of carbon fiber/epoxy in the hoop direction, for a total of 480 plies" "After layup and winding was complete, the cylinder was bagged with cellowrap and then cured in an oven at 137°C for 7 days. There was no postcure. Spencer says initial assessment of the cured cylinder shows that it has porosity of

@@kengself awesome information thanks

Awesome data thanks so much for posting

@TheVicOlive, thanks so much for the awesome data.

Thanks for your feedback

Thanks for your feedback

Thanks for the feedback

You're comparing the young's modulus of a single carbon fiber to the modulus of titanium. The elastic modulus of a composite lamina is only about 135 GPa vs about 100 GPa for titanium. When you consider that about 2/3 of the fibers are in the hoop directions you get .66*135, which is about 90 GPa in the hoop direction. Not a terrible match. Through the thickness is another story. The through thickness modulus is only about 9 GPa.

@@matthew4878 I did not see any info on how they laid up the prepreg, it would be nice to see what ply orientation they used. Good info on the modulus. I was wondering why they only wound in the hoop orientation on the first sub. Normally on gas cylinder winding they use different orientations. I am sure at depth the forces would be coming in at all angles. But not sure though thanks for the data

@@JoediyLab they only used the winder in the hoop direction because they would have wasted a lot of material trying to wind around domes on each end like on an internally pressurized vessel. If you look carefully at that video you'll see shots where the texture of the carbon fiber looks different. What you're seeing is a layer of prepreg that's oriented in the axial direction. This would have been applied by hand. The ratio of 2:1 for hoop to axial fibers comes from the fact that the hoop stress is twice as large as the axial stress for a thin walled pressure vessel. This isn't exactly the case for a thick walled vessel but it's approximately so.

@@matthew4878 good info. I get the impression that not a lot of testing has been done on thick wall vessels. Have you found any info how they applied the prepreg on the newer sub? Thanks for the exchange of information

Thank you for your excellent comment. The website of Pacific Coast Composites states many technical details of the hull manufacturing process used by Spencer Composites for Cyclops 2 (is that the initial pre-launch name for Titan?--the CF hull dimensions appear the same). They mention laying of materiel in both the 'axial' and 'hoop' directions: ...Manufacturing in a generous safety margin: The carbon fiber/epoxy hull of the Cyclops 2 features alternating layers of UD prepreg in the axial direction, and wet-wound carbon fiber filaments in the hoop direction. The hull is 127 mm thick (5 inches vs. the 6 inches planned for Fossett’s earlier craft) and has tested to 2.5 times the 6,500-psi service pressure... No autoclave was used--curing was by 'oven' for 7 days at 137 deg C.

Thanks for the awesome followup. Yes I heard in the titan sub they used a tape laying machine. I will have to check the Pacific Coast site. that is new information for me. But Stockton refused to perform between dive testing.

I computed both the hoop and axial stress as shown in my video and found that indeed the axial stresses appear too high given the layup. kzfaq.info/get/bejne/l7aHZLR4tNrFdZ8.html

Thanks so much for the positive feedback

Thanks, what would you like to see more of? Composites?

Thanks for the feedback 😸

Thanks for the feedback

Thanks for the feedback

Thanks for the feedback

Thanks for the feedback

I built a hydrostatic tester that can test to 500 feet. Been thinking of doing some carbon fiber testing

@@JoediyLab that would be very interesting.

You my fren, are based. I never knew ligben existed. Thanks.

Actually I was mistaken, pressure vessel is 5'10" outside diameter.

If ID is 56 and thickness is 5, then OD is 66, not 61 (OD = ID + 2T)

@@JoediyLab if OD is 5'10" or 70," then ID is 60" given a wall thickness of 5" thickness to mean radius ratio is used to differentiate. Mean D is 65, so R = 65/2 = 32.5 with t/D = 5/32.5 = 0.154, 1/20 would be 0.05, 1/10 is 0.1, so between 1/6 and 1/7. Thick wall pressure vessel.

@@nevisstkitts8264 You're correct.

Thanks

Thanks

Interesting info, thanks

Thanks

Yes, unless it is designed right, Thanks for the comment

Thanks

On this sub, according the dimensions, radial pressure on the CF tubular section is 400 bars and axial pressure is 1440 bars on these section of 5 inches thick. Very strong on a "plastic" material.

Yes these are good questions, I would question the bonding of the CF to the titanium as well, hopefully the engineering analysis will shed some light on the actual failure.

concur on the adhesive ... utter BS. And it wasn't even a "friction fit" at Sea Level ... supposedly this was intentional as Rush wanted the adhesive to act as a "cushion" between the CF Hull and Titanium flange mate point expansion/contraction rates. From the photos I saw of the salvaged end caps, there were no CF remnants affixed ... just peeled off.

My logic worked just like yours! 😇😬

Yes the acoustic system would have went off milliseconds before the crush.

@@JoediyLab Looks like his acoustic warning system was basically a portable non destructive test which worked, but at that point its too late to do anything about it.

@@BABA-ws5eo yes, when you hear the alarm it might be too late

So how would you test the integrity of the material?

@@uzzuzz9320 Good question. There may be other non-destructive test methods that I'm not aware of.

What about x-ray, we use to x-ray folding wind lock pins?

@@JoediyLab maybe. I've heard that this material is basically transparent to x-rays but I couldn't say for sure.

​@@matthew4878 they can xray through semi-trailers carrying iron. They can most certainly XRay through this. The problem would be that unlike Ultrasound, there is no depth perception - what you see is all the 667 layers of CF superimposed over one another. You would see fractures but not delamination. To see delamination on XRay would mean directing the rays longitudinally along the tube rather than across its diameter - it would be very difficult to visualise a slight delamination (fractions of a mm) at some point along the length of the tube as you are now necessarily using much higher energy to penetrate a 12 foot long section of CF rather than 5 inches - this would be in the MegaVolt range - As the XRay energy goes up, the ability to discriminate between structures lying very close together, or even see small structures at all, decreases. Such high energy photons blast through small structures to be able to penetrate the full length of the structure. To blast through the 12 foot haystack, you wont see the needle, effectively. There are Ultrasound machines that can penetrate hundreds of feet through the earth and rock. They arent handheld, though. analysing this 5 inch thick CF tube is most certainly possible using Ultrasound - but it would be very time consuming (and therefore costly) as every layer of laminate at different depths would need to be examined at every point along its length- not achievable with XRay. It would be possible to measure the gap between laminates, any deviation from expected measurements, or inconsistencies in these measurements indicating delamination would be well demonstrated. The Ultrasound would direct transversely through the 5 inch thick CF, and be able to look at each layer and compare each to adjacent layers. Unlike XRay, the penetrability of the sound beam (wavelength) can be adjusted to optimally demonstrate structures at different distances from the source. Its like comparing Sonar to a photograph. Given the different compression coefficients of the 2 materials, the Titanium shrinking onto the CF at great pressure could only have produced cracking in the CF, common sense seems to suggest. Maybe they didnt want to know the answer? Maybe they knew if it was tested theyd have to build another pressure vessel, at great expense? Or, admit that he should have built out of Titanium from the start. Common sense again dictates that any sealed structure that is going to compress and expand must be made from materials that compress and expand equally? The length of the join is also a concern - as the titanium expands when rising, it was then only this glue that prevented water from entering between the end caps and the CF? This thing was a death trap.

Good question, epoxy adhesive is used in aerospace applications with very good luck, But not at those kinds or pressures.

Yes, thanks for the comments

Thanks for the info

Thanks

Thanks for your feedback, Yes I am looking forward to seeing the results.

good ideas. Not sure if bulkheads would have worked as the deformation would have occurred in between the bulkheads.

Interesting, I gather you are from the UK, All of the documentation I have read states: "freestudy.co.uk/statics/complex/t1.pdf" "A cylinder is regarded as thin walled when the wall thickness t is less than 1/20 of the diameter D." Wondering if there are different standards between our countries.

@@JoediyLab Been a while since I studied maths, but it seems 1/10 of radius is probably somewhere fairly adjacent to 1/20 of diameter :)

Sounds good to me. Thanks

@@JoediyLab You can delete those comments if you want. I won't say anything if you don't :)

No problem, Thanks for the all of the interaction. It is always good to discuss with folks who have different backgrounds.

Depends on the epoxy, some are rated for very cold temps. Such as aerospace applications.

That conjecture was based on a statement made by James Cameron. Just was repeating whas was said in the media. I indicated this in the video

@@JoediyLab Okay, I must have missed that. I recall hearing his first statement and it think was before any debris had been recovered. It will be interesting to hear more details, based what was learned during the recovery.

The undamaged "landing frame" suggests it may have been jettisoned before the implosion intentionally with the intent to surface. If it was found a distance from the debris field, this would add to this argument. This has been noted on another video (cannot remember which one).

@@timecentral3134 I have heard that, but without knowing how it was attached, there is no way to know if it was jettisoned or if it became separated during the implosion. I think it's the latter, not the former, because without it, the sub would not have been able to land on the launch vehicle.

I just read an article in The New Yorker that quoted someone familiar, “The report that I got immediately after the event-long before they were overdue-was that the sub was approaching thirty-five hundred metres,” he told me, while the oxygen clock was still ticking. “It dropped weights”-meaning that the team had aborted the dive-“then it lost comms, and lost tracking, and an implosion was heard.” So I guess they knew there was a problem and they attempted to abort the dive. That means the occupants knew they were in deep shit. Not a nice way to go. I'm still not convinced that the frame was jettisoned. It would have no way to land on the launch vehicle without it.

I believe someone calculated the hull strength, I heard from several engineers. Look at some of the posts, one engineer did show some calculations. Thanks

New mic and pop filter has been ordered

Thanks for the comment, In pressure tanks, carbon fiber is strong in tension, I have seen applications of using carbon fiber filament winding for pressure vessels. That is pressure pressing from the inside to the outside.

@@JoediyLab Oh yes, it's really common, even scuba tanks are made of it, but in compression under that kind of pressure I think new and different forms of lay-up need to be explored.

Great question, according to Wikipedia definition, Young's modulus is both in tension or compression, thanks

The Young’s modulus of carbon fibre is not reversible. Carbon fibre has no compressive strength at all - the epoxy matrix is the source of the compressive strength with transfer to the carbon fibre as a tension load normal to the applied force (if any of the carbon fibre runs in that direction).

@@allangibson8494 thanks for the added information

Very much so. There are many epoxy adhesives with different qualities. Some epoxy foams and fills, like for honeycomb etc. Epoxy adhesives are also rated for temp use and flexibility. Epoxy adhesives also have different strength properties. Preparation is also critical. There is some conjecture about whether the titanium was properly prepared. Images from the recovery. Show clean surfaces. Which could indicate the the epoxy let loose. We will have to wait and see. Thanks for the great question

Thanks Joe. Looking forward to your next video.

Another question Joe. There were reports of a “crackling” sound in the aft section at depth. Significance? Since failure of the carbon fiber apparently comes without warning, could the crackling point to an epoxy bond failure?

@@move4dts more than likely a delamination occuring. As a result of cycling failure.. Or the bonding failing from CF and titanium flange

@@move4dts thanks, in the process of getting materials together for composite testing.

Depending on the resin system used there may be issues. But it gets very cold in space, but that is under tension and not compression.

@JoediyLab Thanks Joe, keep up the great analysis and insight. Very much appreciate...

Yes, that is correct, Just depends when orientation you are looking at. In a sub we are more concerned about compression then tension

Mic is on order

@@JoediyLab I’ll be back 👍

@@surf2257 thanks so much

You bet

That was the older sub, I believe that one failed when tested

@@JoediyLab Thank god for that.

Mic on order

Already purchased, thanks

my mistake, 5'10" outside diameter.

Epoxy adhesive is a common method of bonding metal alloys to carbon fiber. You just cannot bolt carbon fiber sections together. But yes there are many issues with the way the sub was designed and not tested between dives. Thanks for your feedback.

Thanks for the comment, yes and I was referring the the pressure of the outside pressure hull being forced inward by the seawater pressure. But did not mention that the pressure hull would also be in tension from the inside pressing outward.

All very good points, I think that is one reason the coast guard continued the search even after hearing the anomaly. They were not sure if it was related to the titan or not, but yes they could have announced that just like they heard the banging noises.

Yes, Thanks for your comments.

Not sure of you are referring to me but in the video I said pulling.

Good point, thanks