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Post by fish on Jun 26, 2023 9:05:51 GMT 12
OceanGate CEO Stockton Rush reportedly said that the carbon fibre used for the vessel's hull came at a "big discount" from Boeing as it was past its aeroplane shelf life. Does anyone know how carbon fibre can have a shelf life? It doesn't corrode, it isn't radio active so can't decay. Is it some sort of oxidation process? I thought the whole point of carbon fibre was that it didn't oxidise? (oxidising being a form of rust)
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Post by DuckMaster on Jun 26, 2023 9:13:48 GMT 12
OceanGate CEO Stockton Rush reportedly said that the carbon fibre used for the vessel's hull came at a "big discount" from Boeing as it was past its aeroplane shelf life. Does anyone know how carbon fibre can have a shelf life? It doesn't corrode, it isn't radio active so can't decay. Is it some sort of oxidation process? I thought the whole point of carbon fibre was that it didn't oxidise? (oxidising being a form of rust) From a composite site: Fabrics and prepregs degrade gradually over time. In composite laminates it is not the fiberglass, carbon fiber or Kevlar fibers themselves that initially degrade. It is the sizing or fiber primer that degrades over time. Sizings are placed upon the fibers to make them more compatible with a given resin system during cure. As time goes on fiber sizings diminish, weakening the future link between the fabric and the resin, thus yielding a possibly weaker composite laminate. The exact storage life of most sized fabrics is not always listed on a technical data sheet. Often one may need to research further into a manufacturer’s technical manuals for an expected shelf life of a fabric sizing. Fiber sizing life can range from a year to beyond five when stored under favorable conditions. For prepreg materials a general shelf life is first a year. After a year or after initial expiration some fabrics and prepregs may be re-tested for performance against its original stated performance specifications and bonding characteristics. In the case of a DIY project possibly using expired fabrics it is important to test a laminated section of the expired fabric to ensure its quality is up to par for its intended use.
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Post by eri on Jun 26, 2023 9:14:27 GMT 12
am guessing the dive profile was something like
almost at the bottom, the crack sensors in the carbon started going off
they aborted the dive and started ascending normally
more and more sensors started going off even as the ascent was reducing pressure
they prayed the sensors would stop, audible cracking was heard from the hull
they dumped the weight bags triggering an uncontrolled rapid ascent
but so many carbon filaments had failed by now and were continuing to fail that it was too much and the whole tube failed
the titanium end caps would have been blown out the ends
now the 3 clusters of imploded parts start settling back to the bottom about 500?mt above and to the side of the wreck
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Post by fish on Jun 26, 2023 9:16:41 GMT 12
Does anyone know how carbon fibre can have a shelf life? It doesn't corrode, it isn't radio active so can't decay. Is it some sort of oxidation process? I thought the whole point of carbon fibre was that it didn't oxidise? (oxidising being a form of rust) From a composite site: Fabrics and prepregs degrade gradually over time. In composite laminates it is not the fiberglass, carbon fiber or Kevlar fibers themselves that initially degrade. It is the sizing or fiber primer that degrades over time. Sizings are placed upon the fibers to make them more compatible with a given resin system during cure. As time goes on fiber sizings diminish, weakening the future link between the fabric and the resin, thus yielding a possibly weaker composite laminate. The exact storage life of most sized fabrics is not always listed on a technical data sheet. Often one may need to research further into a manufacturer’s technical manuals for an expected shelf life of a fabric sizing. Fiber sizing life can range from a year to beyond five when stored under favorable conditions. For prepreg materials a general shelf life is first a year. After a year or after initial expiration some fabrics and prepregs may be re-tested for performance against its original stated performance specifications and bonding characteristics. In the case of a DIY project possibly using expired fabrics it is important to test a laminated section of the expired fabric to ensure its quality is up to par for its intended use. Mwahahaha, so the carbon fibre was fine. It just wouldn't stick to the resin.... I have been wondering about that 'other' key component in the carbon fibre tube, the resin. Nothing mention about that so far. Wonder if he just used some West System epoxy and got on with it?
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Post by eri on Jun 26, 2023 9:23:06 GMT 12
theorizing here
carbon being carbon, wants to form molecular bonds with just about everything
carbon as diamond is very stable as all the bonds are to itself?
but carbon as carbon fibre has lots of unattached bonds and so bonds with mainly water from the air, but also anything else in the air like dirt, dust, skin cells, which all try to absorb water
so vacuum packed and frozen bare carbon should last the longest, but even then the carbon would slowly absorb the packing molecules
bare carbon filaments on a dusty shelf in a warehouse would weaken the fastest
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Post by DuckMaster on Jun 26, 2023 9:24:39 GMT 12
am guessing the dive profile was something like almost at the bottom, the crack sensors in the carbon started going off they aborted the dive and started ascending normally more and more sensors started going off even as the ascent was reducing pressure they prayed the sensors would stop, audible cracking was heard from the hull they dumped the weight bags triggering an uncontrolled rapid ascent but so many carbon filaments had failed by now and were continuing to fail that it was too much and the whole tube failed the titanium end caps would have been blown out the ends now the 3 clusters of imploded parts start settling back to the bottom about 500?mt above and to the side of the wreck There's no evidence to suggest they were ascending. There's no evidence to even suggest they had "crack sensors". One article stated that the technology doesn't exist to check the structure for cracks. The comms and the transponder failed simultaneously at 3600m, they were headed for 3800m. The wreckage was found directly below the point where the transponder cut out. The ballast was attached in such a way that it could be released manually by rocking the sub back and forth. So an implosion would of released it in a similar way. I think it's more likely the dive profile went something like... We're at 3600m almost there. Followed by an air of excitement Then 2ms later everyone is gone The energy of the implosion would of vaporized all the electronics and most if not all of the carbon fibre tube. The occupants would of turned to ash.
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Post by GO30 on Jun 26, 2023 12:01:25 GMT 12
Ah so they got to 3600, bugger so close.
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Post by bleh on Jun 26, 2023 13:27:05 GMT 12
Found this interview with the CEO, here is a snippet:
The hull-monitor system
POGUE: How many backup systems do you have for the thing collapsing?
RUSH: So the key on that one is, we have an acoustic monitoring system. Carbon fiber makes noise. There're millions of fibers there. There are 667 layers of very thin carbon fiber in this five-inch piece.
It makes noise, and it crackles. When the first time you pressurize it, if you think about it, of those million fibers, a couple of 'em are sorta weak. They shouldn't have made the team.
And when it gets pressurized, they snap, and they make a noise. The first time you get to, say, 1,000 meters, it will make a whole bunch of noise. And then you back off, and it won't make any noise until you exceed the last maximum.
And so when, the first time we took it to full pressure, it made a bunch of noise. The second time, it made very little noise.
We have eight acoustic sensors in there, and they're listening for this. So when we get to 1,000 meters, if all of a sudden we hear this thing crackling, it's, like, "Wait, did somebody run a forklift into it? You know, has it had cyclic fatigue? Is there something wrong?"
And you get a huge amount of warning. We've destroyed several structures [in testing], and you get a lotta warning. I mean, 1,500 meters of warning.
It'll start, you'll go, "Oh, this isn't happy." (LAUGH) And then you'll keep doin' it, and then it explodes or implodes. We do it at the University of Washington. It shakes the whole building when you destroy the thing.
So that's our backup for the hull. And we're the only people I know that use continuous monitoring of the hull.
POGUE: So if you heard the carbon fiber creaking—
RUSH: If I heard the carbon fiber go pop, pop, pop, then the gauge says, "You're getting a whole bunch of events."
POGUE: Could you get three hours back to the surface in time?
RUSH: Yes. Yes, 'cause what happens is once you stop going down, the pressure, now it's easier. You just have to stop your descent. And so that's what we did a lotta testing on. You know, what kinda warning do you get?
And as I said, the warning is about 1,500 meters. It's a huge amount of pressure from the point where we'd say, "Oh, the hull's not happy" to when it implodes. And so you got a lotta time to drop your weights, to go back to the surface, and then say, "Okay, let's find out what's wrong."
POGUE: Well, what is left to worry about?
RUSH: What's left to worry about is the things people don't worry about, which is: you're on a ship in the open ocean. I worry more about people falling and having a head injury—breaking their arm—collarbone. You know, you're on a boat. The most dangerous thing is the boat.
POGUE: You call that more dangerous than this ?
RUSH: Yes. Once you've been sealed inside this, we have four days of life support. That is the safest place on planet Earth. The entire world could be destroyed. A nuclear bomb could take out the ship. And we for four days, we're alive. End of four days, we're dead. (LAUGH)
It is like we just put you in the world's safe, and it doesn't matter what happens outside. As long as you scrub the carbon dioxide and add oxygen, you're gonna be fine for a while.
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Post by em on Jun 26, 2023 13:52:05 GMT 12
Found this interview with the CEO, here is a snippet: The hull-monitor system POGUE: How many backup systems do you have for the thing collapsing? RUSH: So the key on that one is, we have an acoustic monitoring system. Carbon fiber makes noise. There're millions of fibers there. There are 667 layers of very thin carbon fiber in this five-inch piece. It makes noise, and it crackles. When the first time you pressurize it, if you think about it, of those million fibers, a couple of 'em are sorta weak. They shouldn't have made the team. And when it gets pressurized, they snap, and they make a noise. The first time you get to, say, 1,000 meters, it will make a whole bunch of noise. And then you back off, and it won't make any noise until you exceed the last maximum. And so when, the first time we took it to full pressure, it made a bunch of noise. The second time, it made very little noise. We have eight acoustic sensors in there, and they're listening for this. So when we get to 1,000 meters, if all of a sudden we hear this thing crackling, it's, like, "Wait, did somebody run a forklift into it? You know, has it had cyclic fatigue? Is there something wrong?" And you get a huge amount of warning. We've destroyed several structures [in testing], and you get a lotta warning. I mean, 1,500 meters of warning. It'll start, you'll go, "Oh, this isn't happy." (LAUGH) And then you'll keep doin' it, and then it explodes or implodes. We do it at the University of Washington. It shakes the whole building when you destroy the thing. So that's our backup for the hull. And we're the only people I know that use continuous monitoring of the hull. POGUE: So if you heard the carbon fiber creaking— RUSH: If I heard the carbon fiber go pop, pop, pop, then the gauge says, "You're getting a whole bunch of events." POGUE: Could you get three hours back to the surface in time? RUSH: Yes. Yes, 'cause what happens is once you stop going down, the pressure, now it's easier. You just have to stop your descent. And so that's what we did a lotta testing on. You know, what kinda warning do you get? And as I said, the warning is about 1,500 meters. It's a huge amount of pressure from the point where we'd say, "Oh, the hull's not happy" to when it implodes. And so you got a lotta time to drop your weights, to go back to the surface, and then say, "Okay, let's find out what's wrong." POGUE: Well, what is left to worry about? RUSH: What's left to worry about is the things people don't worry about, which is: you're on a ship in the open ocean. I worry more about people falling and having a head injury—breaking their arm—collarbone. You know, you're on a boat. The most dangerous thing is the boat. POGUE: You call that more dangerous than this ?
RUSH: Yes. Once you've been sealed inside this, we have four days of life support. That is the safest place on planet Earth. The entire world could be destroyed. A nuclear bomb could take out the ship. And we for four days, we're alive. End of four days, we're dead. (LAUGH)
It is like we just put you in the world's safe, and it doesn't matter what happens outside. As long as you scrub the carbon dioxide and add oxygen, you're gonna be fine for a while.So in a nutshell they finally cracked all the fibres ? The last few Milliion all cracked at once .
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Post by sabre on Jun 26, 2023 14:32:56 GMT 12
Very enlightning interview. Looks like Eri's theory was bang on the money.
The guy was no dummy and was certainly well qualified in his field..
Stockton received a BSE in aerospace, aeronautical, and astronautical engineering from Princeton University in 1984 and an MBA from the UC Berkeley Haas School of Business in 1989.
"'This is the safest place on planet earth" hmmm. Just goes to show science is often wrong and can create a very false sense of security.
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Post by DuckMaster on Jun 26, 2023 15:46:01 GMT 12
Very enlightning interview. Looks like Eri's theory was bang on the money. The guy was no dummy and was certainly well qualified in his field.. Stockton received a BSE in aerospace, aeronautical, and astronautical engineering from Princeton University in 1984 and an MBA from the UC Berkeley Haas School of Business in 1989. "'This is the safest place on planet earth" hmmm. Just goes to show science is often wrong and can create a very false sense of security. They we'ren't on there way up they were still going down. According to OceanGate the comms system and the transponder are two entirely separate systems with there own power supplies. They lost contact with both simultaneously and at that moment the sub was still in a normal downward descent with all systems operating normally. The guy didn't listen to the science. He didn't listen to the scientific community. And he didn't listen to the advice from experts. He was arrogant, thought he knew best, was operating in a industry with no legally enforced compliance or safety requirements. Aeroplanes can fly and land themselves, but the scientific evidence and the expert opinion clearly states that this is a bad idea. Fortunately legalisation and safety controls prevent joe public from being exposed to some eccentric millionaires plan to eliminate the cost of pilots from aviation. From the same interview: POGUE: Has anyone else said, "Look what Rush did. Maybe we should make ours out of carbon fiber?"
RUSH: No. I don't think there are a lotta people chasing me on this one, unfortunately, but they will eventually. (LAUGH)Here's what he had to say about the viewport: POGUE: And I guess the last thing, we should talk about the view port.RUSH: So the view port is seven-inch-thick plexiglass, acrylic, and that's another thing where I broke the rules. A lot of the submersible industry is run by Pressure Vessels for Human [Occupancy] standards, which acts like a standards body, but it's not a standards body; it's a volunteer group that has come up with some rules.And there was a very well-known person, Clarence Statue (PH), was, like, the king of acrylic. And so he wrote a book—well, he had several books, but one of these is sort of the Bible. And even he admitted that he was super conservative. It has safety factors that—they were so high, he didn't call 'em safety factors, he called 'em "conversion factors."You know, for most things, safety factors are one-and-a-half, two-and-a-half…and it's four to ten. And most of what he was looking at was lower-pressure applications. And so when you look at the charts, we're off the charts.One of the things about acrylic that's really great is, before it fails, at one-third its failure pressure, it will start to "craze." So it'll often be distorted. So you know when that thing's gonna fail. And so when I was looking at this, that view port is—according to the rules, it is not allowed.So there's these weird rules that are out there.It will shrink. It's a semi-solid, the plexiglass; it'll come into the cabin by about three-quarters of an inch—all of the pressure that's there.POGUE: Oh, man. And that's a good thing?RUSH: Well, that's what it is. But the great thing about plexiglass that I love is, you can see every surface. And if you've overstressed it, or you've even come close, it starts to get this crazing effect.POGUE: Okay. And if that happened underwater—RUSH: You just stop and go to the surface.POGUE: You would have time to get back up?RUSH: Oh, yeah, yeah, yeah. It's way more warning than you need.And somewhere else he says
POGUE: So it seems like a lot of the way you made this is by taking off-the-shelf parts and sort of MacGyvering them together. RUSH: Yeah. Pretty much. POGUE: Does that not raise anybody's eyebrows in the industry? RUSH: Oh yeah! Oh yeah. (LAUGH) Yeah, no, I'm definitely an outlier. There's been more intrigue into that than I can go into. But—yeah, I've been considered just totally out of my, you know—"Well, you can't do this." You know, at some point, safety just is pure waste. I mean, if you just want to be safe, don't get out of bed, don't get in your car, don't do anything. At some point you're gonna take some risk, and it really is a risk/reward question. I said, "I think I can do this just as safely by breaking the rules." POGUE: Wow. RUSH: And a lot of people didn't like that. (LAUGH)
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Post by fish on Jun 26, 2023 18:49:25 GMT 12
Very enlightning interview. Looks like Eri's theory was bang on the money. The guy was no dummy and was certainly well qualified in his field.. Stockton received a BSE in aerospace, aeronautical, and astronautical engineering from Princeton University in 1984 and an MBA from the UC Berkeley Haas School of Business in 1989. "'This is the safest place on planet earth" hmmm. Just goes to show science is often wrong and can create a very false sense of security. Ermm, no, Stockton was wrong, not the science. He had a theory. His theory was not tested or proven, and turns it it was wrong. Mainly demonstrated by the fact he (and four of his punters) are dead. There are soo many assumptions he is making in that interview: 1) that pressure increases lineally as depth increases (I've no idea if it does or doesn't, but the rate of change of pressure sure isn't going to be linear). 2) that the fibres popping doesn't weaken the structure 3) that the quantities of fibres will fail in a linear manner. I think even an 8 yr old could work out his explanation is wrong. Yes, the first time you take it to 1,000m you will have a bunch of fibres fail. But sooner or later the thing is going to break. That is when all the fibres go at once. There is no basis at all that fibres popping one at a time has any relationship to predicting a catastrophic failure. He was just day dreaming on that front. Sure it might have sounded great listening to all these fibres popping on the first pressurisation, but why would think you can predict catastrophic failure with that? There are a bunch of different physical phenomena that cause pies / tubes to fail. From a basic pipeline theory, it sounds like he is predicting what we call "slow crack propagation" there is also "fast crack propagation" as well as "hoop stress" and a bunch of other more obscure ways to break a pipe. Just cause you've addressed one means of failure doesn't mean you can exclude all the other means of failure. What interests me is he doesn't appear to mention cumulative fibre pops. This would be the most obvious to me, and would most closely align with the basic phenomena of cyclic fatigued.
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Post by DuckMaster on Jun 26, 2023 18:57:31 GMT 12
The other elephant in the room is that carbon fibre isn't even designed to withstand compressive forces.
The only thing that stops carbon fiber from compressing is the epoxy.
Grab 100 fibres in each hand... Nothing stops you pushing your hands together but you sure as fuck are never get your hands to elongate those fibres.
If the pressure is from the inside out then sure. But in a submarine it's the opposite.
And yes, pressure increases linearly the deeper you go. 1 atm/10m.
One of my kids used to play hockey, his carbon fibre hockey sticks could withstand 100 of kg of pressure when flexed along the shaft. Get it caught in a car door, fall on it the wrong way, or even have someone stand on it and the thing would crumple faster than you can say 'fuck that was expensive'.
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Post by fish on Jun 26, 2023 20:50:49 GMT 12
The other elephant in the room is that carbon fibre isn't even designed to withstand compressive forces. And yes, pressure increases linearly the deeper you go. 1 atm/10m. To be argumentative, the rate of pressure increase is not linear. The absolute pressure is linear. Diving to 10m is a 100% increase in pressure. Diving another 10m to 20m is only a 50% increase in pressure. Descending the last 10m to 3,800m is only 0.263% increase in pressure. When I'm scuba diving, all my issues with equilisation are in the first 10 m, getting the ears to go, mask squeeze etc. Certainly the come on quickly, because there is such a pronounced rate of change of pressure. Yes, I still have to equalise my ears and mask as I drop from 20m to 30m, but this is not nearly as rapid. (Note, I probably shouldn't have gone to 30m, nut I was narked off my chops. Figure free diving is loads safer ;-) ) Anyway, applying this phenomena to Stockton's 'pinging' principal, the fibres are going to ping more in the early stages of the dive, because the rate of change of pressure is greatest. Therefore the fibres may not ping as much at the deeper stages of the dive. The issue is the absolutely pressure is still increasing linearly. This may mean his little early warning system of listening to the fibre's ping was actually flawed.
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Post by DuckMaster on Jun 26, 2023 22:16:09 GMT 12
What a load of crock. Pressure increase is absolutely linear.
In your world either the water some how magically becomes less dense the deeper you go and somehow the water above doesn't compress it. Or gravity decreases the deeper you go or maybe both.
At 10m the pressure is 2 atm.
At 20m it's 3atm
At 50m it's 6atm
At 1000m it's 101atm
On the surface it's 1atm
P = ρgh
If density (ρ) and gravitational force (h) are constants then the only variable is height.
For every 10m you descend the pressure increases by 1atm. It's the very definition of linear.
Nb: give or take small variances in density of the water due to salinity and temperature these differences are infinitesimally small and don't even factor into the maths... eg 1.025kg/L @ 20degC vs 1.0kg/L at 4deg C
You're confusing pressure with Boyles Law which states the volume of gas is inversely proportional to the pressure.
So in the first 10m of diving you will see the greatest change in air volume which is why equalization is so critical in the first 10m and why decompression stops happen in the last 10m.
The greatest change in air volume occurs in the first 10m which is why you experience the need to equalise in the first 10m and after that it becomes easier.
So at 2atm (10m) the air volume in your ears had halved. At 3atm (20m) the volume of air is 1/3, at 4atm (30m) 1/4th.
The pressure is linear but the volume of air is inversely proportional to the pressure.
This is also why the first 10m are the hardest to get down, cause in the first 10m you are pushing half the air out of your wetsuit.
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