In this paper, within the displacement field of the first-order shear-thickness deformation theory (FSDT), transient vibrations of rectangular cross-ply composite plates are studied and dynamic interlaminar stresses are obtained. In the theoretical formulations the effects of all the rotational inertia terms are considered. Also the change in the plate thickness is taken into account due to its important role in the edge effects. The equations of motion are derived by using Hamilton’s principle. It is assumed that the plates have two simply supported opposite edges and the remaining boundary conditions are arbitrary. The obtained equations are solved analytically using Levy’s formulations, the orthogonality relation, and Laplace transform. The function of time is obtained using the results of free vibration and convolution integral. First, time responses are obtained for the case of transient vibration and then the interlaminar stresses are determined by integrating the three-dimensional local equations of motion and utilizing given boundary conditions. The accuracy and effectiveness of the present theory in describing the localized three-dimensional effects are demonstrated by comparing the results of the first-order theory with those obtained from the finite element method.

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