This tiny submarine 2.4 miles under the sea, visiting the relics of RMS Titanic. Can it be found and the crew saved before the air runs out?

[Reynard]

so they found the 2 end caps but nothing of the carbon fiber tube?

That doesn't surprise me, as CFRP composites shatter in high energy failures. Likely there would only be tiny pieces left, and most of those will probably be carried away by any currents in the area.

My PhD was on aspects of CFRP failures, and I've smashed my fair share of the stuff to understand how it behaves.

 

[Bonefish Blues]

That doesn't surprise me, as CFRP composites shatter in high energy failures. Likely there would only be tiny pieces left, and most of those will probably be carried away by any currents in the area.

My PhD was on aspects of CFRP failures, and I've smashed my fair share of the stuff to understand how it behaves.

Me too - at least a bit...

Yours, a fisherman

We call it 'high sticking' a fish, that is, having a rod too far into the vertical plane with a fish close in. Ping goes the top section of the rod.

 

[Reynard]

Me too - at least a bit...

Yours, a fisherman

We call it 'high sticking' a fish, that is, having a rod too far into the vertical plane with a fish close in. Ping goes the top section of the rod.

I used to fish too. Never quite managed to do that, but then again, never really had anything big enough on the hook...

 

[Ming the Merciless]

so they made only one submersible? in 2019 there were hints that something was wrong?

https://www.cnn.com/2023/06/25/americas/submersible-titanic-implosion-deaths-sunday/index.html

excerpt:
And when submersible expert Karl Stanley was aboard the Titan for an underseas excursion off the coast of the Bahamas in April 2019, he felt there was something wrong with the vessel when loud noises were heard and sent an email to Rush, the CEO of OceanGate Expeditions, sounding the alarm on suspected defects.

“What we heard, in my opinion … sounded like a flaw/defect in one area being acted on by the tremendous pressures and being crushed/damaged,” Stanley wrote in the email, a copy of which has been obtained by CNN.

“From the intensity of the sounds, the fact that they never totally stopped at depth, and the fact that there were sounds at about 300 feet that indicated a relaxing of stored energy/would indicate that there is an area of the hull that is breaking down/ getting spongy,” Stanley continued.

When asked for comment about Stanley’s email, a spokesman for OceanGate told CNN they were unable to provide any additional information at this time

well good thing the mounties are looking into it!
"The Royal Canadian Mounted Police is also investigating the incident "
View attachment 696641

That will be a sea horse of course.

 

[Ming the Merciless]

Meanwhile

 

[Ming the Merciless]

This is interesting

https://www.compositesworld.com/articles/composite-submersibles-under-pressure-in-deep-deep-waters

At the time of the Composites World article, the contracted hull cylinder had been produced but not incorporated into a vessel.

OceanGate later rebuilt the vehicle in 2020, when the hull was found to be showing signs of "cyclic fatigue," meaning it would not be safe at 13,000 feet, GeekWire reported.

 

[Reynard]

Interesting.

It does indeed seem that cost was indeed a driving factor for this. And that the manufacturing issues about air bubbles in the layup that I raised earlier are also raised in the article. Plus that the layup that was chosen created a structure that was anisotropic in its properties, which is not the case with steel. I would have expected the presence of chipped strand mat and weave at +/- 45 degrees to also have been present, but evidently not.

Another no-no is that the end cap fixtures were added after the manufacture of the cylinder - common practice is to laminate fixtures and fittings into a component at the layup stage, but on the flip side, it does complicate things. Ergo more cost.

So yes, corners were cut.

 

[Jameshow]

Interesting.

It does indeed seem that cost was indeed a driving factor for this. And that the manufacturing issues about air bubbles in the layup that I raised earlier are also raised in the article. Plus that the layup that was chosen created a structure that was anisotropic in its properties, which is not the case with steel. I would have expected the presence of chipped strand mat and weave at +/- 45 degrees to also have been present, but evidently not.

Another no-no is that the end cap fixtures were added after the manufacture of the cylinder - common practice is to laminate fixtures and fittings into a component at the layup stage, but on the flip side, it does complicate things. Ergo more cost.

So yes, corners were cut.

Why CSM in a high level laminate?

Is it used in F1?

Very bad not to incorporate end cap fixtures too.

 

[Reynard]

Why CSM in a high level laminate?

Is it used in F1?

Very bad not to incorporate end cap fixtures too.

Yes, it is used in racing car applications (and aerospace).

Admittedly it's not used where loading is particularly un-directional, like suspension etc, but while it's not the strongest or stiffest, the randomness of the strands in CSM acts in a similar way to the crystalline structure in metals, where the properties are the same whichever direction the loading is applied in.

 

[Jameshow]

Yes, it is used in racing car applications (and aerospace).

Admittedly it's not used where loading is particularly un-directional, like suspension etc, but while it's not the strongest or stiffest, the randomness of the strands in CSM acts in a similar way to the crystalline structure in metals, where the properties are the same whichever direction the loading is applied in.

Carbon CSM right?

 

[Reynard]

Carbon CSM right?

Mostly.

Some applications use glass fibre chopped strand mat, although those tend to be used in low load / non-structural areas. On aircraft that might be the doors for the overhead luggage lockers. On racing cars, glass fibre chopped strand mat is used for bodywork panels such as on ARCA late-models. I've smashed enough of that stuff up too, to see how it fails.

I've actually still got about a quarter of a Ford Taurus body shell in my shed, the panels of which were kindly donated to me by a lovely chap called John Steward after he totalled his car at Rockingham.

Although in the late 1980s (1987 to be precise), Swallow built an F3 car out of glass fibre chopped strand mat. Of course, it had all the structural rigidity of a blancmange (not what you want in a racing car), which they found out during testing. No computer modelling of composites in those days. I recently bought a job lot of 1987 Motoring Newses which have a number of articles on the project.

 

[Jameshow]

Mostly.

Some applications use glass fibre chopped strand mat, although those tend to be used in low load / non-structural areas. On aircraft that might be the doors for the overhead luggage lockers. On racing cars, glass fibre chopped strand mat is used for bodywork panels such as on ARCA late-models. I've smashed enough of that stuff up too, to see how it fails.

I've actually still got about a quarter of a Ford Taurus body shell in my shed, the panels of which were kindly donated to me by a lovely chap called John Steward after he totalled his car at Rockingham.

Although in the late 1980s (1987 to be precise), Swallow built an F3 car out of glass fibre chopped strand mat. Of course, it had all the structural rigidity of a blancmange (not what you want in a racing car), which they found out during testing. No computer modelling of composites in those days. I recently bought a job lot of 1987 Motoring Newses which have a number of articles on the project.

I'd never heard of carbon CSM.

GF of course, esp on cheaper boats.
Better ones have more WR and unidirectional woving + CSM.

 

[Reynard]

Hexcel in Huntington make the stuff. Amongst many others. I tested a lot of assorted Hexcel-made sandwich structures and composites during the course of my PhD.

Plus chopped strands are used in injection moulding processes as well, not just as a mat in standard lay-ups.

 

[slowmotion]

Interesting.

It does indeed seem that cost was indeed a driving factor for this. And that the manufacturing issues about air bubbles in the layup that I raised earlier are also raised in the article. Plus that the layup that was chosen created a structure that was anisotropic in its properties, which is not the case with steel. I would have expected the presence of chipped strand mat and weave at +/- 45 degrees to also have been present, but evidently not.

Another no-no is that the end cap fixtures were added after the manufacture of the cylinder - common practice is to laminate fixtures and fittings into a component at the layup stage, but on the flip side, it does complicate things. Ergo more cost.

So yes, corners were cut.

Here's a clip of Cyclops 2, aka Titan being made. Gluing the titanium end ring onto the CF tube with a buttering of (presumably) epoxy made me shudder.


View: https://www.youtube.com/watch?v=4PUTbK5AqY8

 

[Reynard]

Here's a clip of Cyclops 2, aka Titan being made. Gluing the titanium end ring onto the CF tube with a buttering of (presumably) epoxy made me shudder.


View: https://www.youtube.com/watch?v=4PUTbK5AqY8

*facepalm*

A butt joint is pretty well much THE weakest way to glue two components together. Again, that's first year undergraduate stuff.

As for the cylinder. It looks largely made from the wound fibres. That means it will be strong in only one direction (across the width). It will not be strong along its length with that type of layup structure, making it prone to collapse.

Yep, deffo done on the cheap. And flies in the face of good, sound engineering practice. For something that has to operate under extreme conditions, you always want to build in a good Factor of Safety - basically belt AND braces.