Free vibration, buckling and postbuckling analyses of laminated composite plates with multiple delaminations are presented. A fInite element method based on a layer-wise laminated composite plate theory is developed to formulate the problem. Geometric nonlinearity in the sense of von Karman and the imperfection in the plate in the form of initial global deflection and initial delamination openings are included. A simple contact algorithm which precludes the physically inadmissible overlapping between delaminated surfaces is proposed and incorporated in the analysis. A sublaminate concept is adopted in the analysis to reduce the computational efforts, and found to be efficient. Numerical results are obtained for through-the-width, circular and rectangular delaminations addressing the effects of the number of delaminations, their lengths and through-the-thickness and axial locations on the critical buckling load and buckling mode shapes as well as free vibration frequency and modes. Postbuckling responses are investigated with respect to different magnitudes and directions of initial imperfections. The effects of material anisotropy and contact condition between delaminated surfaces are also considered. It is found that the proposed approach is very efficient and powerful for solving the above mentioned problems. / Ph. D.