Vibrations of rotating cross-ply laminated circular cylindrical shells with stringer and ring stiffeners

In this paper, the vibration analysis of simply supported rotating cross-ply laminated cylindrical shells with axial and circumferential stiffeners, i.e., stringers and rings, is presented using an energy approach. The effects of these stiffeners are evaluated via two methods, namely: by a variational formulation with individual stiffeners treated as discrete elements; and by an averaging method whereby the properties of the stiffeners are averaged over the shell surface. The effects of initial hoop tension, centrifugal and Coriolis forces due to the rotation are considered in the present formulation. Also, stiffener eccentricity is accounted for. The present formulation is verified by comparison with experimental and numerical results available in open literature. Excellent agreement is observed and a new range of results is presented for rotating shells which can be used as a benchmark to approximate solutions. Detailed studies on the depth-to-width ratios of the stiffeners on the forward and backward frequencies were conducted for the transverse, circumferential and longitudinal modes. (C) 2001 Published by Elsevier Science Ltd.