The finite element method based on transverse incompressibility and layer-wise linear distribution of in-plane displacements is applied to the dynamic problem of composite laminated structures. A modal approach to the complex eigenvalue problem is introduced to save a considerable amount of computation time. Also, specific damping capacity of each mode is obtained by the modal strain energy method. To investigate the effect of the transverse shear on deformation, the strain energies of each stress component are computed. The frequency-dependent damping properties of Graphite/Epoxy composite material are measured to utilize them for the finite element analysis of thick cross-ply cantilevered beams. The result of the modal approach gives a good agreement with the solution of the modal strain energy method. The damping is very high when the composite laminated plates are subject to large transverse shear deformation as well as in-plane shear deformation. The variation of in-plane displacements through the thickness has a great influence on the fundamental frequency and damping of composite plates, especially on the damping of thick ones. The experimental results show that the frequency-dependent material properties should be utilized for the damping analysis of a thick composite structures unlike a thin one.
