glass-reinforced plastic jacket or, possibly, an intermediate heat shield. 



The rings could also be designed to be self-locking. This could 

 be done by allowing for positive interference and shrink-fitting the 

 rings together (Figure 5f ) . Aside from the difficulties in fabrication, 

 this technique precludes later separation of the rings and may be a source 

 of stress concentration if close tolerances are not maintained. The rings 

 could also be made with threads and screwed together (Figure 5g); here the 

 main problem is the stress concentration at the root of the threads. 



One of the most interesting joining and sealing techniques available 

 is the use of adhesives . Adhesives have the significant advantages of low 

 weight and economy of application. They can be used either alone or in 

 combination with other mechanical bonds. 



The availability of epoxies or similar materials with the necessary 

 bonding properties and tensile strengths has not been established. It is 

 felt that the rapidly expanding adhesive technology will be able to provide 

 a suitable material if the need is established. In addition, adhesives 

 have two critical defects which impair their usefulness in deep-submergence 

 applications; one is a problem in joint design and the other a problem in 

 materials . 



An epoxy adhesive was used on the deep-submergence Krupp sphere of 

 the bathyscaphe TRIESTE to hold the three segments of the sphere together „ 

 The joint was a simple glue-line with a layer of epoxy between the two 

 metal surfaces. When the Krupp sphere surfaced after the first deep dive 

 (Dive 61), the two joints were parted. Fortunately, there was no immediate 

 danger to the occupants of the bathyscaphe since the segments were held 



together by the pressure of the water; for further dives, the sphere was 



12 

 held together by a system of rings and bands. 



The failure of the TRIESTE bond was probably caused by the dete- 

 rioration of the epoxy under high compressive loads . Epoxy resins and 

 other adhesives have relatively low Young's moduli and compressive yield 

 strengths. This means, of course, that they may experience excessive 

 deformation when subjected to the same stress as a metal. Conversely, if 

 the adhesive is subjected to the same deformation as a metal, it will 

 carry a very much smaller stress. The models in this report illustrate 

 one type of joint where the adhesive may act as a bond and seal, without 



