You’d think that would be sufficient to contain ~1 atmosphere of pressure, pushing outward, against a vacuum. A freaking ocean sitting on top of you, pushing inward? Not so much.
Carbon fiber is strong in tension, weak in compression.
Using it in a pressurized aircraft, such as a Boeing 787, is playing to its strengths.
Using it in a submarine hull, exposed to EXTERNAL pressure, where it is weakest, is just foolish.
Using “expired” fiber for a critical manned structure, strikes me as being criminally negligent.