The main body of the submarine was wrapped in 5 inches of carbon fiber tape, maybe some experts here can tell us if that is actually safe or not
Carbon fiber is outstanding for tension loads. Compression, peel, not so much. Think of it this way. Try pushing one end of a rope from the other end. It’s the same with carbon fiber. All the carbon fiber is doing in a compression vessel like this is holding the epoxy matrix together.
(Been in the industry over 20 years)
Essentially it was a plastic vessel with carbon fiber reinforcing. Carbon fiber has excellent tensile strength, compressive strength, not so much.
I see no additional reinforcement at the ends where the bow and stern are attached, just the same thickness throughout.
There is a reason most deep diving submersibles look like one or more spheres strung together, a sphere is the strongest shape possible, as you get away from a spherical shape, you start to weaken the structure.
Carbon fiber is the darling of aerospace construction due to its light weight and high tensile strength, neither of which is paramount in undersea craft construction.
But, what do I know, I am 50< and a white guy.