Effects of flexural boundary conditions on failure and stability of composite laminate with cutouts under combined in-plane loads

In the present study, an investigation on the effects of flexural boundary conditions on prebuckling and postbuckling responses, failure loads and characteristics of a quasi-isotropic [i.e., (+45/−45/0/90)2s] square laminate with and without a central cutout of various shapes is carried out under combined in-plane loads [i.e., uni-axial compression combined with in-plane shear (positive and negative)] using finite element method. The finite element formulation is based on the first order shear deformation theory in conjunction with the von Karman’s assumptions to incorporate geometric nonlinearity. The 3-D Tsai-Hill criterion is used to predict the failure of a lamina while the onset of delamination is predicted by the interlaminar failure criterion. It is observed that under combined loading conditions, buckling and postbuckling strengths and failure loads of the laminate are reduced by the introduction of a cutout at the center of the laminate, irrespective of boundary conditions. It is also noted that the laminate with and without cutout has maximum buckling, first-ply failure and postbuckling strengths (at a particular value of transverse deflection) for BC3 (i.e., clamped on all edges) boundary conditions whereas these values are minimum for BC1 (i.e., simply-supported on all edges) boundary conditions, for both directions of shear load.