The chief advantage of each of the materials used thus far has been 

 their relatively high strength-weight characteristics. However, another 

 desirable characteristic for hull materials to be used in many under- 

 water vehciles at deep depth is transparency. For example, a high trans- 

 parency of hull material to gamma rays would be helpful in the detection 

 of underwater radiation, and transparency to visible rays would be advan- 

 tageous in such applications as hull material for oceanographic research 

 vehicles and instrument casings. 



Glass is a material. we].l knouii for its transparency. However, very 

 little data are available on the compressive strength-weight characteristics 

 of glass. The rather poor reputation of glass as a structural material 

 has been based on experience under tensile loads, where serious effects 

 of scratches and other flaws and imperfections on ultimate strength have 

 been observed. 



The lack of any test data on the strength of glass under biaxial 

 compression led to the exploratory tests described herein on 20 un- 

 stiffened long glass cylinders. These tests were conducted under 

 hydrostatic pressure to determine whether glass deserves consideration as 

 a hull materia], for deep-depth application. This report summarizes the 

 tests, compares the results with existing theory, discusses the strength- 

 weight merits of glass, and outlines the areas of research required before 

 glass can be considered as a hull material. 



DESCRIPTION OF CYLINDERS 



Twenty cylinders of Pyrex brand "double-tough" pipe were selected 

 at random from open stock. "Double-tough" pipe is composed of No. 7740 

 barosilicate glass in a semitempered condition. In a semitempered con- 

 dition No. 7740 glass has a Young's modulus E of 8.96 x 10 psi,a 



References are listed on page 14. 



