VIBRATIONS OF A STIFFENED COMPOSITE SHELL

The natural frequencies and modes have been obtained for a stiffened and unstiffened composite shell composed of a cylinder with spherical end caps. Comparison of these are made to those obtained for an unreinforced cylindrical shell having various edge conditions. The results indicate that at the higher circumferential wave numbers, the frequencies of the unreinforced shell are independent of the end conditions. The frequencies of the ring-stiffened composite shell lie between the corresponding frequencies of the unstiffened shell and that of the isolated ring stiffener for circumferential wave numbers m greater than or equal to 1. Above a critical circumferential wave number, the stiffeners raise the value of the frequencies while below that number, they reduce their values. (Author)