Ultimate strength analysis of imperfect composite plates under both in-plane compressive load and lateral pressure using Ritz method

This paper investigates the ultimate strength analysis of imperfect composite plates under both in-plane compressive load and lateral pressure using Ritz method. In this study, the first order shear deformation plate theory has been applied and the small deflection theory is also considered therefore the obtained results for thin plates could be a little bit off however the results for relatively thick plates are more reliable. The formulations are based on the concept of the principle of minimum potential energy. The laminates are simply supported at the loaded ends as well as the unloaded edges. The in-plane lateral expansion is allowed for all edges however they are kept straight. To investigate the failure analysis, Hashin failure criterion has been applied and also two different models for degradation of stiffness has been used. The first model is complete-ply stiffness degradation model that apply the degradation of properties to the whole ply, and the second is regional stiffness degradation model which degrade the properties of that region. The instantaneous degradation of material properties is used for failed ply or region of failed ply. In addition to find the first and last ply failure loads, the number of failed plies and coordinates of failure points in first and last plies has been obtained. Finally, the results obtained by the proposed method have been validated by results available in the literature.