ring segments. Upon release of pressure , the ring segments expand 

 more than the outer jacket so that the two become firmly locked together, 

 the outer jacket being in residual tension and the ring segments compris- 

 ing the hull structure being in residual compression. This technique 

 offers many possibilities for combining the best properties of high- 

 strength nonweldable materials, and, at the same time, for circumventing 



the obvious shortcomings of each. Two possible combinations are shown 



70 

 in Figure 21. Short has suggested the use of variable-thickness shell 



segments as a means of eliminating the longitudinal bending action 

 between adjacent stiffening elements and thus permitting a state of "pure 

 membrane" behavior. This innovation is shown in Figure 21 where a web- 

 stiffened titanium sandwich hull core of varying thickness between webs is 

 encased in a fiberglass jacket. 



Another of the more promising structural concepts for the design and 

 fabrication of cylindrical pressure hull structures for deep-depth applica- 

 tion is the sandwich concept. Structural engineers in the aircraft industry 

 have long recognized and taken advantage of the favorable strength-weight 

 and thermal-dispersion characteristics of sandwich-type construction in 

 the design of modern high-speed aircraft and missiles. In studying the 

 literature, however, it has been found that the loading conditions encounter- 

 ed in the&e applications have dictated sandwich structural arrangements 

 that would be of no direct use to the naval architect in the design of pres- 

 sure hulls for submersibles. Most of this work (e.g., see Reference 71) 



126 



