Fundamental Frequencies of Elliptical Composite Cylinders with Circumferentially Varying Fiber Orientation

Abstract

The fundamental vibration frequencies of thin-walled elliptical composite cylinders for which the fiber orientations in some or all of the layers vary linearly with circumferential location are discussed. The study is motivatedbypreviousworkthatdemonstratedthatacircumferentiallyvarying fiberorientationschemecanbeused to improve the axial buckling capacity of an elliptical composite cylinder. At issue then is the degree to which fundamental frequencies are influenced by the circumferentially varying fiber orientation. Circular cylinders are also considered, so an additional finding of the study is the influence of cylinder cross-sectional geometry on the fundamental vibration frequency, with all other cylinder geometric and material parameters remaining the same. The results, which are based on finite element models of the elliptical and circular cylinders, indicate that, even for what is considered a significant range of fiber orientations that vary linearly with circumferential location, the fundamental frequencies of both elliptical and circular cylinders are not significantly influenced. On the other hand, the circumferential wave numbers are influenced. The frequency results for circular cylinders are substantiated by the work of other researchers.