Abstract
The methods of the orthogonality of principal modes and the state variables technique are used to investigate the dynamic response of symmetric cross-ply laminated composite plates by solving the equation of a higher-order shear deformation plate theory. Exact solutions of simply supported rectangular plates are presented for various loadings. The results obtained using the higher-order theory (HSDT) are compared with those obtained by the Reissner-Mindlin shear deformation plate theory (FSDT) as well as the classical laminate theory (CPT).