ABSTRACT 



Cyclic tests were conducted on two ring-stiffened com- 

 posite cylinders consisting of high-strength aluminum rings 

 surrounded by thin metallic jackets. Both cylinders were 

 subjected to pressure variations corresponding to depths from 

 to 10,000 ft. The estimated static collapse depths were 

 about 15,000 ft. Both models failed at about 12,000 cycles. 



INTRODUCTION 



The David Taylor Model Basin is currently engaged in a study of the 

 feasibility of composite construction for use in deep-diving submarine 

 pressure hulls. Composite construction is a means of utilizing high-strength 

 nonweldable materials for deep -submergence applications. A complete de- 

 scription of composite construction appears in Reference 1." As part of 

 this program, two cylindrical models of conjiosite construction. Models DSRV- 

 lA and DSRV-IF, were designed for the purpose of conducting exploratory 

 cyclic tests to determine the fatigue strength of structures with this type 

 of construction. 



Models DSRV-IA and DSRV-lF were similar to Models DSRV-1 and DSRV-IL 



2 

 which were tested under static loading at the Model Basin. This report 



presents the results of the cyclic tests on Models DSRV-IA and DSRV-IF. 



DESCRIPTION OF MODELS 



Model DSRV-IA consisted of cylindrical segments of 7079-T6 aluminum 

 with a yield strength of 76,000 psi, surrounded by a weldable aluminum jacket 



with a yield strength of 30,000 psi. The geometry for Model DSRV-lA was 



2 

 identical to that of Model DSRV-IL, which was statically tested, except 



that on Model lA the aluminum jacket replaced the HY-100 steel jacket used 

 on Model IL. Model lA was originally constructed to determine the struc- 

 tural characteristics of a composite model with an aluminum jacket under 



References are listed on page 12, 



