TexasRebel said:

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There could have been a large shear load on the adhesive due to material thermal property differences between the carbon fiber and Ti.

The temperature gradient was over 40F from exterior surface to interior (assuming min. 68F inside).

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Mechanics is not my forte so I may be way off....

You are pointing out the different thermal coefficients of Ti and Carbon fiber. People upthread also mentioned the galvanic issues. What about the general difference in mechanical behavior under compression?

Doesn't the inside diameter of a cylinder under radial compression decrease and increase slightly back and forth as it is compressed and relaxed? Would the titanium ring inside diameter and the carbon hull ID change a different amount under these massive loads? Would that be enough to induce shear forces and potentially cause cracks around that joint?

OTOH, as a vulnerability this might be less than the risks associated with imperfections in the layup and cycle fatigue across the hull.

Here is the patent for Rush's carbon fiber monitoring system:

https://patents.google.com/patent/US11119071B1

Toothpaste:

sounds unpleasant:

https://nypost.com/2023/07/11/titan-sub-victims-likely-realized-their-fate-between-48-to-71-seconds-before-deaths/

I also don't think it was THAT negatively buoyant, I can't imagine it would go into a "freefall" as he described

It certainly seems reasonable to say that he will be known for the rules he broke.

Tookieclothespin said:

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sounds unpleasant:

https://nypost.com/2023/07/11/titan-sub-victims-likely-realized-their-fate-between-48-to-71-seconds-before-deaths/

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Is this speculation or verifiable facts?

TexasRebel said:

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I think the rules broke him.

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Isaac Newton is undefeated.

bmks270 said:

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Tookieclothespin said:

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sounds unpleasant:

https://nypost.com/2023/07/11/titan-sub-victims-likely-realized-their-fate-between-48-to-71-seconds-before-deaths/

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Is this speculation or verifiable facts?

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One expert's opinion. I know investigations are ongoing but who knows if we will truly ever know, communications at depth are not anything like they are on the surface and they may not have had time to clearly communicate each even which occurred.

They probably knew something was a little wrong, CEO says nothing to worry abou-

Well yeah.

Worrying is futile.

There are reports that if you put a light to one side of the carbon fiber, you could see light on the other side from gaps and imperfections and the gradual damage to the carbon fiber.

I haven't seen that before, except on obviously very much failed pieces of CFRP. Also if it were true it would probably become an NDI technique.

The Fife said:

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I haven't seen that before, except on obviously very much failed pieces of CFRP. Also if it were true it would probably become an NDI technique.

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Yeah, I'm not an expert on carbon fiber but the hull was 5 inches thick and should have had fibers running in multiple directions so seeing anything through it sounds impossible.

bmks270 said:

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Tookieclothespin said:

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sounds unpleasant:

https://nypost.com/2023/07/11/titan-sub-victims-likely-realized-their-fate-between-48-to-71-seconds-before-deaths/

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Is this speculation or verifiable facts?

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I think it's speculation by an expert who is piecing together a story based on what is actually being released to the public. I, on the other hand, am not an expert on anything related to the story.

bthotugigem05 said:

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bmks270 said:

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Tookieclothespin said:

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sounds unpleasant:

https://nypost.com/2023/07/11/titan-sub-victims-likely-realized-their-fate-between-48-to-71-seconds-before-deaths/

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Is this speculation or verifiable facts?

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One expert's opinion. I know investigations are ongoing but who knows if we will truly ever know, communications at depth are not anything like they are on the surface and they may not have had time to clearly communicate each even which occurred.

They probably knew something was a little wrong, CEO says nothing to worry abou-

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I'm not optimistic but the fact that most of the instrument bay external to the hull was recovered suggests maybe there will be some data available. Upthread someone said the inertial navigation system was legitimate. It should be fairly robust and would have logging of telemetry. So assuming that was not inside the hull, perhaps that can be recovered.

4000-meter-manned-submersible-titanic-survey-expedition-equipped-ixblues-inertial-navigation

www.ixblue.com/maritime/navigation/inertial-navigation-for-subsea-operations/

If they took that many shortcuts, I'm not confident they had any data recording beyond maybe what depth at what time.

chickencoupe16 said:

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The Fife said:

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I haven't seen that before, except on obviously very much failed pieces of CFRP. Also if it were true it would probably become an NDI technique.

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Yeah, I'm not an expert on carbon fiber but the hull was 5 inches thick and should have had fibers running in multiple directions so seeing anything through it sounds impossible.

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if you watch the videos of them making it, they did not crisscross the carbon fiber. it was all parallel.

Burdizzo said:

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TexasRebel said:

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I think the rules broke him.

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Isaac Newton is undefeated.

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I think Newton took a L with the whole alchemy thing.

bthotugigem05 said:

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I also don't think it was THAT negatively buoyant, I can't imagine it would go into a "freefall" as he described

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The design of the sub was that it did 'freefall' but it was like 100-feet per minute or something. If it lost power, it was already in a free fall and, from what I've read, they could have moved around in the sub to cause the ballast to drop and go back to the surface. Losing power had nothing to do with the implosion.

this is a good video about the "engineering" of the sub.

The most salient points are about Stockton Rush's comments about "pilot error" and "certification organizations". Stockton was an idiot.

TexasAggie_02 said:

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chickencoupe16 said:

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The Fife said:

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I haven't seen that before, except on obviously very much failed pieces of CFRP. Also if it were true it would probably become an NDI technique.

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Yeah, I'm not an expert on carbon fiber but the hull was 5 inches thick and should have had fibers running in multiple directions so seeing anything through it sounds impossible.

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if you watch the videos of them making it, they did not crisscross the carbon fiber. it was all parallel.

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Holy ****, you serious? I've only dealt with CFRP applications with AFP layup where you have an environment within the vessel (aircraft/whatever) that's higher pressure than the outside but their design just makes no sense to me at all.

The Fife said:

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TexasAggie_02 said:

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chickencoupe16 said:

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The Fife said:

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I haven't seen that before, except on obviously very much failed pieces of CFRP. Also if it were true it would probably become an NDI technique.

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Yeah, I'm not an expert on carbon fiber but the hull was 5 inches thick and should have had fibers running in multiple directions so seeing anything through it sounds impossible.

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if you watch the videos of them making it, they did not crisscross the carbon fiber. it was all parallel.

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Holy ****, you serious? I've only dealt with CFRP applications with AFP layup where you have an environment within the vessel (aircraft/whatever) that's higher pressure than the outside but their design just makes no sense to me at all.

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watch the video I posted. They didn't even put the CF tube into an autoclave.

Re-reading it, I think his point might have been that if it went nose down then the ballast would no longer have any effect and all of the passengers would be in a pile on top of each other at the bottom, since there were no seats

bthotugigem05 said:

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Re-reading it, I think his point might have been that if it went nose down then the ballast would no longer have any effect and all of the passengers would be in a pile on top of each other at the bottom, since there were no seats

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The sub had neutral buoyancy without ballast. The thrusters were just to move around near the ocean floor, not go down to the wreck or ascend back up.

The ballast gave it negative bouncy so it would float to the bottom. Even if it was slightly nose down, it was just falling and the thrusters were not controlling anything. There is no reason a loss of power would suddenly cause everyone to fall forward to the nose and the sub goes down like a rocket. Not that I can see anyway.

agracer said:

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Tookieclothespin said:

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sounds unpleasant:

https://nypost.com/2023/07/11/titan-sub-victims-likely-realized-their-fate-between-48-to-71-seconds-before-deaths/

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this guy is FOS

Quote:

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"The Titan changes position and falls like an arrow vertically because the 400 kilos (880 pounds) of passengers that were at the porthole unbalance the submersible," he wrote.

"Everyone rushes and crowds on top of each other. Imagine the horror, the fear, and the agony. It had to be like a horror movie," added the expert, who believes that everything happened during 48 to 71 seconds of free fall.

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Videos of the Titan do not show everyone crowded towards the front of the vessel. They're spread out in the space and I'd guess (although with the idiot owner/pilot I could be wrong) that was standard operating procedure for a decent. Just like a small plane, the pilot wants the weight distributed evenly.

This Marin guy is just trying to get his 15m of fame.

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i dont really get the crowding part either. unless the vessel just took a nose dive (q: how?) and they weren't belted in (no idea if they were secured in) and gravity did it's only job.

The Fife said:

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I watched through it a couple of times and had to dig a little deeper

https://www.engineering.com/story/the-titan-tragedy-a-deep-dive-into-carbon-fiber-used-for-the-first-time-in-a-submersible

Quote:

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A 2017 article in Composite Weekly describes the carbon fiber construction of the Cyclops 2 (later renamed as the Titan) as "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."

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Building it this way, with no autoclave cure and I'm assuming no meaningful inspection for voids or porosity, FOD, wrinkles, ... is criminally dumb. Go for extra thickness but don't bother with ensuring there's a good bond because who needs that? Probably no attempt to scan the IML or OML for damage between dives either.

I'm surprised it didn't fatigue out before it finally did, but I guess in a way they did their fatigue testing with actual passengers inside and got a data point for what the life limit is.

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100% agree. Even more critical when fibers are in compression.

Tanks on space flight vehicles typically have a metal liner that is plastically deformed during testing (autofrettage), preloading the interface and reducing strain extremes, increasing cycle life. The liner also allows for autoclave use to remove air bubbles and voids. Even so, failures STILL occur due to voids between layers.

In the of the Titan, with no autoclave and hand-laid layers, a single void in the exterior and can result in high-pressure water getting pumped further into voids, finding low-pressure pockets to travel into, and gradually cutting into the polymer matrix. 5600 psi water finds a way. Waterjet cutters run at 10X that pressure, but 5600psi still does damage.

This process does weaken the structure, especially with cycling. Combine that with local fiber buckling, stress concentrations, and shearing from water pressure, and it's easy to see how this could fail.

NASAg03 said:

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The Fife said:

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I watched through it a couple of times and had to dig a little deeper

https://www.engineering.com/story/the-titan-tragedy-a-deep-dive-into-carbon-fiber-used-for-the-first-time-in-a-submersible

Quote:

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A 2017 article in Composite Weekly describes the carbon fiber construction of the Cyclops 2 (later renamed as the Titan) as "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."

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Building it this way, with no autoclave cure and I'm assuming no meaningful inspection for voids or porosity, FOD, wrinkles, ... is criminally dumb. Go for extra thickness but don't bother with ensuring there's a good bond because who needs that? Probably no attempt to scan the IML or OML for damage between dives either.

I'm surprised it didn't fatigue out before it finally did, but I guess in a way they did their fatigue testing with actual passengers inside and got a data point for what the life limit is.

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100% agree. Even more critical when fibers are in compression.

Tanks on space flight vehicles typically have a metal liner that is plastically deformed during testing (autofrettage), preloading the interface and reducing strain extremes, increasing cycle life. The liner also allows for autoclave use to remove air bubbles and voids. Even so, failures STILL occur due to voids between layers.

In the of the Titan, with no autoclave and hand-laid layers, a single void in the exterior and can result in high-pressure water getting pumped further into voids, finding low-pressure pockets to travel into, and gradually cutting into the polymer matrix. 5600 psi water finds a way. Waterjet cutters run at 10X that pressure, but 5600psi still does damage.

This process does weaken the structure, especially with cycling. Combine that with local fiber buckling, stress concentrations, and shearing from water pressure, and it's easy to see how this could fail.

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And just like that the days of carbon fiber subs were over.

bonfarr said:

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That article is based on a theory from a guy in Spain that says he studied the reports after the sub was found. What doesn't make sense to me is he says the sub lost power after descending to 5500 feet and it went into a free fall to the bottom. He says the 5500 feet coincides with when the sub lost contact with the surface vessel.

From what I have read the sub lost contact 1 hr and 45 minutes into the dive and I thought I read the typical trip to the bottom was 2 hours so the sub should have already been at a much deeper depth when it lost contact, very near to the wreck when contact was lost.

I don't know how this guy can say the sub lost power when there are no other reports of that occurring. I still think they traveled about 85% of the way to the bottom and the thing just came apart.

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It's just his opinion at the moment.

Pluralizes Everythings said:

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bonfarr said:

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That article is based on a theory from a guy in Spain that says he studied the reports after the sub was found. What doesn't make sense to me is he says the sub lost power after descending to 5500 feet and it went into a free fall to the bottom. He says the 5500 feet coincides with when the sub lost contact with the surface vessel.

From what I have read the sub lost contact 1 hr and 45 minutes into the dive and I thought I read the typical trip to the bottom was 2 hours so the sub should have already been at a much deeper depth when it lost contact, very near to the wreck when contact was lost.

I don't know how this guy can say the sub lost power when there are no other reports of that occurring. I still think they traveled about 85% of the way to the bottom and the thing just came apart.

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It's just his opinion at the moment.

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You mean it isn't the Spanish Inquisition?