Replies

But epoxy is good under compression. It is the properties of the overall matrix that matters. And it is weaker in compression, but it is only a factor of a couple Delamination is a different problem than failure becasuse of crushing the matrix.

The structural problem is knowing how it failed. The reason a compressed vessel normally fails is actually buckling - a sphere or hoop deforms out of round, and at a certain stress this becomes untable and the sphere collabses into two "flat" plates. That is why in a normal submarine hull you have large I-beam hoops - to keep the hull round so that strength is controlled by compressive hoop stresses and not buckling.

Carbon fiber is extremely strong in tension. In compression it sucks. There was about 6000 psi of compression on that hull

And the compressive strength of expoxy can be as high as 25 kpsi. It's a good engineering problem. Submarine hull steels used to be about 80kpsi and are more recently 120kspi or more. But harder steels are not necessarily tougher steels. It is a tradeoff between strength and toughness and in a military vessel you want a tough steel to withstand explosive devices or impacts with seamounts in addition to overall hull strenght.

So the problem with carbon fibre epoxy hulls is that the vessel becomes quite thick in comparison with the volume. Normal submarine hulls using high strength steels or titanium [if you can afford it - and the Russians could and the US couldn't] are pretty thin by comparison.

It was perhaps a flawed choice but it requires a detailed analysis to understand exactly how bad it was and not just a oh, carbon fibre is weak under compression [weaker is not weak] and so it is not an actual analysis. Now, as in all engineering practice, the burden of proof is on the designer and not the detractor and the designer clearly failed in the burden of proof.