Vibration of antisymmetric angle-ply composite annular plates of variable thickness

Based on first order shear deformation theory, free vibrational behaviour of antisymmetric angle-ply composite annular plate is investigated. The thickness variations are assumed to be linear, exponential and sinusoidal along the radial direction. The equilibrium equations are obtained from which the coupled differential equations are derived in terms of displacement and rotation functions. These functions are approximated using splines to obtain the system of algebraic equations in terms of spline coefficients where the equation becomes a generalized eigenvalue problem by combining the boundary conditions. This problem is solved for finding eigenfrequencies and corresponding eigenvectors. This study is conducted for clamped-clamped and clamped-free boundary conditions. Detailed parametric investigation is carried out to determine the influences of radii ratio, number of layers, ply orientations and materials on the frequencies of plates. The primary results of this study are compared with those available in the literatures.