78 

 by Pulos and Yang. 



The question of how important interlaminar shear resistance is and 

 what influence it has on instability strength of multilayered shell 

 structures should be studied. Tests of structural models having different 

 numbers of layers comprising a cylindrical shell should be conducted to 

 study the relationship of different geometric parameters to ultimate load- 

 carrying capacity. Also, available theories for the stresses in and 



buckling of multilayered cylinders require examination. An excellent 



79 

 summary of such analyses has been given by Ambartsumian. 



A strong possibility exists that underwater vehicles of the future will 



utilize spherical shells as the main pressure hull or, more likely, to close 



off the ends of basically cylindrical or spheroidal hulls. Krenzke has 



recently presented the first results stemming from a major structural 



Q Q 



research effort on stiffened and unstiffened spherical shells. From 



tests of machined models, designed to investigate both elastic and in- 

 elastic behavior, he has obtained collapse pressures on the order of two 

 to three times the values reported by earlier investigators. The collapse 

 strength of those models which failed elastically could not be predicted by 



Q 1 



the classical small-deflection theory of Zoelly or any of the available 



28 82 

 large-deflection theories. ' However, Krenzke was able to achieve 



collapse pressures which were 70 percent of the predictions from the 



linear theory of Zoelly. Another significant result reported by Krenzke 



is that, contrary to the belief of others, the buckling coefficient appears 



129 



