“Carbon fiber is strong in tension, weak in compression.”
I’m wondering how using a monocoque technique would change those dynamics.
My main experience is with carbon fiber windsurfing equipment and bicycles. My 12 pound road bike frame has 30k+ miles carrying my 225lb butt around with no issues, and when monocoqued windsurfing booms came out I stopped breaking them.
Stresses on a bike frame are a bit more complicated than on a pressurized tube.
Seems to me:
The seat tube, forks, and the head tube would be in compression, lengthwise (not from outside pressure like a submarine hull)
The top tube, down tube, and stays would be in shear and tension.
In the submarine application, the hull tube is in compression on the thickness of the hull. In your bicycle, the down tube and forks (for example) are in compression along the length of the tube.