The Titan Submarine Imploded Due To Micro-Cracks In The Carbon Fiber Hull - Has A Carbon Fiber Bottle Broken/Exploded On Anyone?

[SkeeterHawk]

I heard on the news that the Titan Submarine that was exploring the Titanic was made of Carbon Fiber and they warned against using that material because micro cracks would be exacerbated by the frequent pressure changes, so the more the sub was used, the more potential for catastrophic failure. The pressure at 12,500 feet below sea level is about 370 to 380bar, so this is very much in the range that we are playing with.

This would lead one to believe that the CF bottle is a little like a balloon that gets weaker the more it is inflated, so if you have a very regular shooter that is filling many times a day, this would exacerbate this problem and there may be failure before the expiration date on the bottle.

What are your thoughts??

Jonathan

 

[Benj312]

The carbon fiber bottles we use have been tested and found to meet the design criteria for pressurization and de-pressurization cycles.

 

[markhooper]

I heard on the news that the Titan Submarine that was exploring the Titanic was made of Carbon Fiber and they warned against using that material because micro cracks would be exacerbated by the frequent pressure changes, so the more the sub was used, the more potential for catastrophic failure. The pressure at 12,500 feet below sea level is about 370 to 380bar, so this is very much in the range that we are playing with.

This would lead one to believe that the CF bottle is a little like a balloon that gets weaker the more it is inflated, so if you have a very regular shooter that is filling many times a day, this would exacerbate this problem and there may be failure before the expiration date on the bottle.

What are your thoughts??

Jonathan

well I'll stick with aluminum or steel.. while carbon fiber is a lot lighter than say my oxygen tank.. I just trust metal more.. but I have heard of people using a old water pressure tank for a additional air compressor storage and wonder why they have a destroyed shop.. pressure vessel is normally hydro test at 1.5x operating pressure and well said water tank is only rated for 60 psi.. then figure putting in 100+ psi and any corrosion and I don't see how it works even the first time..
that said I don't know enough about carbon fiber.. maybe it's stronger as a pressure vessel? it's the opposite for the submarine..
I don't have a clue how they could possibly test the submarine other than sending it down empty.. because I am guessing to pressure test it.. it would need to be inside of a air tank and up to our operating pressure on its outside.. because I don't know if it is exactly the same pressure exerted inside vs outside..
for those who don't know what hydro test is.. it's basically filled with water and pressurerized and see if it holds.. water, or hydraulic fluid would just spray out if ruptured.. but air or any type of gas.. hydrogen, oxygen or whatever will rupture with something similar to a explosion..
so it's possible that they have a way to hydro test a submarine but it could be a destructive test, just like if a oxygen tank or propane tank is tested and fails.. it's broken.
Mark

 

[markhooper]

The carbon fiber bottles we use have been tested and found to meet the design criteria for pressurization and de-pressurization cycles.

just don't exceed it's rating and I personally wouldn't use it if past it's rated life unless recertification..
Mark

 

[Stubbers]

CF bottles have an aluminum interior and CF skin or shell, where the pressure is acting on the inside trying to expand the aluminum interior, within its rating it doesn't, and the CF reinforces the aluminum, you exceed the rating of the interior aluminum and combined reinforced CF, you get bad news. That is generally 3-4x the fill pressure by design.

On the Titan sub the CF was wrapped on the exterior of the sub, with a titanium or some kind of steel thin shell inside, which made this design weak because the carbon fiber had to withstand the extreme pressure differential between 1 and 400 back to 1 atm over and over, creating those micro-fractures over time which resulted in eventual catastrophic failure. Had they wrapped the exterior in a steel strong enough to withstand any yielding whatsoever, well then there is no point to wrap in carbon the interior, but that would be a better suited comparison for reversing the roles with CF tanks and that CF sub...

So in short, the Titans CF shell was subjected to expansion and contraction with pressure directly acting on it as well as being under-designed, it was supposed to be 7" not 5" thick....where as your CF skinned aluminum tube is not under designed and the CF is not directly exposed to pressure that will yield it to fail.

-Matt

 

[Stubbers]

The two failure events aren't even comparable either, a large HPA tank failing could at worse shoot the tank around like a weak rocket, bouncing off walls until empty, unless bolted down, because its slowly releasing (depending on size of rupture, a small enough rupture may not even really move the tank much or too violently, no different than cracking your tanks valve open while not connected to a gun) a small volume of very highly compressed air into what may as well be considered infinitely larger air at atmospheric pressure. Slow explosion (cf tank) vs near sudden implosion (Titan Sub)

The Titan sub, upon failure, created a compression event from the weight of all the water (400 atm's) collapsing in on that little 1 atm air bubble that caused that volume to be reduced by 400x, I am unsure of the interior volume of that sub but it was likely reduced to about a 1-3 cubic foot, 400 atm / 6000 psi air bubble or a series of them equal to after all the violence, igniting the volume possibly multiple times along the way to a temperate hotter than the surface of the sun. The body can only take 3.5 atm's or so, so within 2 micro seconds or 1/500th of a millisecond the occupants were exposed to unlivable pressure, far faster than any neuron in their brain can fire.

Saying they were Thano's out of existence doesn't even really do proper justice as a finger snap probably takes 100x longer than the Titan's failure event.

-Matt

 

[MikeVV]

What Stubbers said...
The "carbon fiber" cylinders are a mix, or a hybrid of an aluminum cylinder, with a layer or three of carbon fiber over the aluminum.

Thought everyone knew that by now.

Mike

 

[SkeeterHawk]

the CF reinforces the aluminum, you exceed the rating of the interior aluminum and combined reinforced CF, you get bad news. That is generally 3-4x the fill pressure by design.

Thanks for the thoughtful response, @Stubbers

I agree, and I knew this. I wondered if going to atmosphere to 400bar back and forth would cause the CF to fail, and then the aluminum backer to fail.

the Titans CF shell was subjected to expansion and contraction with pressure directly acting on it as well as being under-designed, it was supposed to be 7" not 5" thick....where as your CF skinned aluminum tube is not under designed and the CF is not directly exposed to pressure that will yield it to fail.

I moved over to CF because of the lesser thermal expansion coefficient of it compared to the Aluminum bottles that I had previously used.

It seems like there has never been any failures of CF bottles within their certification date, the point of my post, because they are designed correctly.

 

[BlackICE]

One youtuber said that the sole viewing window wasn't rated to even 1/2 the pressures needed at the depth the sub went. If that's true, only an idiot, if they knew that would get into that sub even for free, let alone paying 250K!

I betcha many on this forum use CF tanks long after the 15 years allowed in the USA, citing in other countries the limit is 30 years. But after the 15 years no company in the US will certify it. So you are just hoping that it is good for 30, not verifying it.

 

[Stubbers]

Thanks for the thoughtful response, @Stubbers

I agree, and I knew this. I wondered if going to atmosphere to 400bar back and forth would cause the CF to fail, and then the aluminum backer to fail.


I moved over to CF because of the lesser thermal expansion coefficient of it compared to the Aluminum bottles that I had previously used.

It seems like there has never been any failures of CF bottles within their certification date, the point of my post, because they are designed correctly.

Yea scuba tanks and the like are designed very safely to not even yield within ~2.5x the fill pressure where as the Titan sub cut many corners and used CF in a way that basically flipped the materials around while using ones comparable to a soda can as a thin metal external shell. Apples to oranges.

 

[SkeeterHawk]

But after the 15 years no company in the US will certify it. So you are just hoping that it is good for 30, not verifying it.

Great Point @BlackICE I imagine that there are a small percentage of us that have those dates in our calendars...or wherever that we can remember it.

 

[Stubbers]

Great Point @BlackICE I imagine that there are a small percentage of us that have those dates in our calendars...or wherever that we can remember it.

In theory, the lifespan of a correctly cared for steel diving cylinder can be 40 years, while aluminum diving cylinder can serve for up to 20 years and 10000 pressure tests. In the real world seldom any tank reaches that age. I doubt anyone exceeds 10,000 fills in 20 years, that would be 1.4 fills a day avg every day for 20 years. The greater pressure differential between your pressure cycles the more the fatigue, but that is another rabbit hole to dive down. I personally feel confident using my tank for the duration of my life provided I never cause physical damage or corrosion. Filling once a week would take 194 years to achieve 10,000 pressure cycles.

-Matt

 

[steve-l]

I heard on the news that the Titan Submarine that was exploring the Titanic was made of Carbon Fiber and they warned against using that material because micro cracks would be exacerbated by the frequent pressure changes, so the more the sub was used, the more potential for catastrophic failure. The pressure at 12,500 feet below sea level is about 370 to 380bar, so this is very much in the range that we are playing with.

This would lead one to believe that the CF bottle is a little like a balloon that gets weaker the more it is inflated, so if you have a very regular shooter that is filling many times a day, this would exacerbate this problem and there may be failure before the expiration date on the bottle.

What are your thoughts??

Jonathan

You do not know what caused the implosion..........nobody does yet, if ever. The news media today is the least reliable it has ever been. Stop spreading bull poop!

 

[Long_Gun_Dallas]

Tanks we use fail at many times the pressures they ever actually see. Even if one was to fail, it would most likely just develop a leak. I've never once heard of one of the carbon wrapped tanks just exploding.

 

[Hy-Score]

I heard on the news that the Titan Submarine that was exploring the Titanic was made of Carbon Fiber and they warned against using that material because micro cracks would be exacerbated by the frequent pressure changes, so the more the sub was used, the more potential for catastrophic failure. The pressure at 12,500 feet below sea level is about 370 to 380bar, so this is very much in the range that we are playing with.

This would lead one to believe that the CF bottle is a little like a balloon that gets weaker the more it is inflated, so if you have a very regular shooter that is filling many times a day, this would exacerbate this problem and there may be failure before the expiration date on the bottle.

What are your thoughts??

Jonathan

I find this to be an interesting observation, and question.

 

[OldSpook]

How hard would that sub have had to have bumped into the wreck to propagate a fracture?

 

[Rudolph Hucker]

Carbon fibre was never designed for hydrostatic forces.

It was made to resist tension.

 

[Kraemer99]

Tanks we use fail at many times the pressures they ever actually see. Even if one was to fail, it would most likely just develop a leak. I've never once heard of one of the carbon wrapped tanks just exploding.

I was behind a guy at the paintball field filling his 4500psi tank when it gave up. Not really an explosion but rather a sudden whoosh of air. When he removed the cover off the bottle there was a tangle of carbon fiber on the side where it failed. Paintball tanks take a beating.
The dive shop owner here told me that in all the years he had never seen or even heard of a 3000psi steel tank failing no matter how old it was. Thought that was interesting…..

 

[jps2486]

well I'll stick with aluminum or steel.. while carbon fiber is a lot lighter than say my oxygen tank.. I just trust metal more.. but I have heard of people using a old water pressure tank for a additional air compressor storage and wonder why they have a destroyed shop.. pressure vessel is normally hydro test at 1.5x operating pressure and well said water tank is only rated for 60 psi.. then figure putting in 100+ psi and any corrosion and I don't see how it works even the first time..
that said I don't know enough about carbon fiber.. maybe it's stronger as a pressure vessel? it's the opposite for the submarine..
I don't have a clue how they could possibly test the submarine other than sending it down empty.. because I am guessing to pressure test it.. it would need to be inside of a air tank and up to our operating pressure on its outside.. because I don't know if it is exactly the same pressure exerted inside vs outside..
for those who don't know what hydro test is.. it's basically filled with water and pressurerized and see if it holds.. water, or hydraulic fluid would just spray out if ruptured.. but air or any type of gas.. hydrogen, oxygen or whatever will rupture with something similar to a explosion..
so it's possible that they have a way to hydro test a submarine but it could be a destructive test, just like if a oxygen tank or propane tank is tested and fails.. it's broken.
Mark

There’s steel and then there’s steel. Lower grade steel alloys can have internal inclusions, processing stress cracks and is subject to fatigue failure. Higher grade steel alloys are better in those regards but are more costly. No material is perfect.

 

[Rudolph Hucker]

An interesting video that one of the lads put up on another forum.......