If that were the case, it would fail on first descent. The fact that they made the trip several times makes me suspect fatigue from stress on the carbon fiber hull.
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I'd be more curious about how the two different materials react to temperature/pressure changes. If they're not shrinking and expanding with the changes at the same rates than the epoxy is being asked to do something it isn't made to do. Gaskets are made to make up for those kind of differences over repeated exposures, hard bonding "glues" are not.

... I assume these people are smarter than I am and there must be a way to explain this concern away.
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I've never used epoxy resin that looked exactly like that. The shit we use in the shop for Fiberglass and Carbon fiber lays on clear and dries clear.

Either way, if i were supposed to get on this thing and had learned that the cap was being held by epoxy resin, i'm noping the fuck out.

Resin is pourus. It can fill with air pockets. It degrades. It's soft enough to sand down by hand. It can take days to cure properly, and while it cures it can shrink and shift.

And we never, ever use epoxy resin to bond fiberglass straight to metal like that. Even when we glass in metal brackets to fiberglass panels, it's never with just epoxy. You put fiberglass matte down over the base of the bracket and then glass that into the fiberglass panel.

Again, that's automotive shit. Not sure about this here.

All i can say is we wouldn't do it like that to a car. /Shrug.
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Not necessarily, it's possible that the epoxy could deteriorate from repeated flexing if the materials it's holding together are moving due to repeated drastic changes in pressure. Especially if it's holding together different types of materials (like titanium & carbon fiber) that may flex at different rates.
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The more I think about this I feel like it's like parachuting with an experimental material made out of spider webs and then not tested. Like what do you mean not tested? I want them to throw a 200lb mannequin out of the plane over a thousand times with zero failures before I'd even think about using it.
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The mannequin is already dead, that's a shitty way to start your adventure...
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At least two people on board had curry as a steady part of their diets. I'm not saying it was their fault, but C'mon, Pakistan?
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Exactly. If the Carbon fiber is flexing, it'd crack the epoxy.

Ive never heard of using epoxy resin to bond fiberglass/carbon fiber to metal in the manner in which they did.

Matter of fact, we don't fill gaps on cars using Fiberglass/Marglass in any areas that can flex.

It's popular in restomods to fill some gaps, such as fender extensions, quarter panel extension, rocker panels etc with Marglass or Fiberglass to give it that seamless look.

Problem is, cars flex. And over time, you'll end up with big ass cracks where you thought you had a nice smooth finish. Shit, these materials shrink when they heat up.

We have to avoid leaving customer cars in the sun because often times these cars will have gaps and seams filled with these materials and exposure to too much heat (the sun) will cause the materials to shrink and crack.

FUCK no would i trust resins and composites for something like this. Fuck no.

I get it, cars are different than million dollar subs. But goddamn, some of these rules still apply here.
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One more thing, when we DO use materials like Marglass (An extra strong fiberglass filler w/resin) to adhere straight to steel, we at least hit the steel with a 36 grit D.A so the marglass can adhere better.

I'm guessing their titanium cap had a perfectly smooth finish. From my automotive experience, that's just one more no no. The rougher the surface, the better the adhesion.
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One MORE thing. When we do use these sorts of materials on a car, we put the car outside to bake in the sun for WEEKS. Weeks, dudes. To allow the gasses to escape while it cures and continues to harden and shrink.

I got a car here right now that has cracks in the freakin' rear deck lid filler panel because whoever built the damn thing filled the factory body gaps with fiberglass resin. We parked the car outside while its not being worked on and now it has cracks. This is a painted vehicle already. Oh well.

Yeah, there's no way i trust their process. Just slathering resin onto carbon fiber and dropping titanium onto it like, "Ok, finished!".
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Apologies if this has already been posted, but I just saw it. Interesting YouTube video about what would have happened when the sub imploded. According to this (starting around 8:15) they wouldn't have just be crushed - the pressure differential would have superheated the air and incinerated them. Of course, it would have happened in about a millisecond, so they never would known what happened or had a chance to experience any pain.


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What makes me think that glue and flange joint had something to do with it is Im not sure that carbon fiber hull would ever be strained much at all in its normal operations at 13,000 ft. That damn thing was really built to withstand 30,000+ feet. It was 5 inches think - overkill really. Richard Branson's deep flight challenger also used carbon fiber and was built to go to 37,000 feet and from pictures doesn't look nearly as thick as the Titan. People make all these statements about carbon fiber flexing and cracking over time but I'm not sure that applies when the operating strain is less than 50% of its rating. I just have a hard time believing engineers used to working with this stuff who know exactly what the external operating pressure is would screw something up so bad.

But that 2 inch joint where the titanium ring gets glued onto the hull just looks weak as hell. There's obviously a gap there otherwise the ring wouldn't be able to slide over the hull. And within that tiny gap is some type of glue - if that glue fails the tiniest bit it's lights out.
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Deepsea Challenge has walls only 2.5 inches thick but it's steel.
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It's been way too long since I took engineering classes, but I'm trying to figure out what that failure would look like. Let's assume that you have two pieces - a fuselage and a nose cap - and they're connected with superglue.

You've got low pressure inside the sub and high pressure outside it. The high pressure would force the two pieces together, right? Think of the pressure on the fore and aft both pushing in. The pressure on the sides are canceling each other out, but trying to compress in, which is not overly relevant.

Now we think about the little gap with the superglue. The pressure is pushing on it from the sides as well. You've got the front/back pressure that's squeezing the fuselage and nose cap together, which is good, but there's always going to be a gap there with the glue. If that's the weak spot, then eventually the pressure is going to break through, right?

So now you have an ultra-high pressure water jet (think hose with your thumb on it) suddenly entering the passenger compartment. As that pressure goes through the constricted glue gap, will that produce an even higher pressure in the fuselage/nose cap junction that will overcome the front/back force and blow the nose cap off? That might explain why it's in good shape.

If my physics is wrong and it just equalizes the front back pressure, then you have the problem of an ultra-high-pressure water jet inside the passenger cabin. I would think that that would pretty quickly carve a hole where the fuselage and nose cap meet, separating the two pieces as well. So maybe it's a little slower, but the same end result of the nose cap separating.

The other scenario would be that the jet doesn't carve a hole, in which case the submersible fills with water in about 1 second and sinks, but that doesn't seem to be the case.

What's your theory on how this failure would happen?
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