It worked for a few dives because the loads were mostly all in compression but eventually matrix cracking caught up and caused a failure. Had the vessel been subjected to positive internal pressure it would have exploded at a very low pressure
Back in the days when boring 50 year old white engineers were still 20 year old innovators, carbon fiber filament wound pressure vessels were the state of the art for solid fuel rocket motor cases.
They had to be pressure tested before filling with the solid fuel so they were filled with water and pressurized to a thousand or so psi. They had so many leaks due to voids and air pockets from the winding process that some looked like sprinkler heads.
No big deal because they used a rubber liner to seal the leaks which was adequate because the vessels only saw positive internal pressure and they only had to live for a couple of minutes.
for long-fiber composites, I don’t THINK the matrix is designed to carry any load. That should not be going into any stress calc. Maybe in short-fiber...but I am less familiar with them.
Iirc the matrix only supports the long fibers - keept them in place and oriented. Kinda like a web of an i beam. I could be incorrect.. The main concern is the fiber in the geometry of the layup that are most stressed starting to fail, which in turn transfer the load to the next fibers, which are in a slightly less mechanically advantageous position to bear the increasing stress due to reduction in stress bearing area...it cascades until catastrophic brittle failure.
I own a tool and die company, I make the tools that make the rubber liners too. :)
I’m wondering how much weight savings played into his thinking with carbon fiber also.
I mean with aerospace it’s obvious, but given transport and logistics of a standard steel submersible both on land and the water I can’t help but think that huge savings in weight had something to do with them choosing it as well.
“If the reports are true, the vessel was almost completely hoop wound carbon fiber tows, which means the vessel had virtually zero strength in the longitudinal direction because there were no carbon fibers in that direction to hold it together. only weak epoxy type resin.”
Didn’t they test it without people in it in actual water at depth?? Multiple times??
Thank you. Another good response about CF. Some of my favorite failures was when we tested fuselage burst strength and breaking wings. Good times when you get to destroy an aircraft on purpose. Carbon fiber is great and fails spectacularly. Basically zero yield unlike metal structures. It is very strong until it isn’t...
https://youtu.be/Ai2HmvAXcU0