The videos I've seen of the construction of the tube section show it to just be carbon fibre, about 5" thick, wound radially only (not that it would matter much as the pressure is the wrong way for the tensile strength of carbon fiber to do anything). Effectively, the cylinder portion was made from epoxy resin. The titanium end caps were just glued on. The process by which they were glued was amateur to say the least. No degassing of the resin, no climate control, done in an open warehouse (no contamination control).