Kai J.

The growing application of composite laminates in industry as structural components, demands a deeper knowledge of their dynamical behaviour and buckling analysis. Noor presented a solution for stability and vibration of multi-layered composite plates based on three-dimensional elasticity theory by solving equations with the finite difference method. However, with suitable modifications, analytical models for predicting modal frequencies can also be used for solving inverse problems. It is clear from the literature that the behaviour of composite plates subjected to free vibration has not been well established. None of approximate solutions obtained covered different types of theories, geometric factors, and different lamination stacking sequence of composite materials. This paper deals with free vibrations analysis of multilayered plates. A set of equations for the modelling laminated composite plates has been derived. These dynamic equations of the plate are derived using a higher order shear deformation theory with a displacement field that includes five unknown parameters. Equivalent single layer theories herein used; they are based on the same assumptions as the classical and first order shear deformation plate theories, except that the assumption on the straightness and normality of the transverse normal is relaxed. This generalized formulation covers symmetric as well as antisymmetric layer combinations. It is also a general case for classical, lower order and previous higher order shear deformation theories. Finally, the governing equations are solved by Ritz method. A general equivalent-layer formulation is employed to analyse the effect of various theories (CLPT, FSDT and HSDT) on the natural frequencies of laminated composite plates. Moreover, the effect of fibber orientation on the natural frequency is investigated. In order to have better understanding of the dynamic behaviour of different plates with different parameters associated to the problem, a dynamic analysis of composite plates is performed.