The Influence of Axial Compression on the Free Vibration Frequencies of Cross-ply Laminated and Moderately Thick Cylinders

Abstract

In this study, the free vibration behavior of axially compressed cross-ply laminated composite cylinders is investigated using a semi-analytical shell finite element based on a consistent first order shear deformable shell theory, which includes the influences of rotatory inertia and thickness coordinate/radius ratio. First, a verification study is conducted to validate the axisymmetric shell finite element used in this study and, for the non-compressed cases, the free vibration frequencies obtained using the finite element developed are found out to be in excellent agreement with the published results found in the literature. The same element is also validated for first-ply failure analysis and good agreement is observed with the first-ply failure loads obtained using a shear deformable and curved shell element. Then, numerical results for free vibration analyses are presented for axially compressed composite cylinders having different boundary conditions and for which the level of axial compression is kept below the corresponding linear buckling and first ply failure loads. It is observed that, the fundamental free vibration frequencies decrease sharply for axial load levels higher than about 60~80% of the buckling loads of the cylindrical structures considered. It is also determined that the first-ply failure load is lower than the buckling load for some of the thicker cylinders.