Postbuckling response of square laminates with a central circular/elliptical cutout

The finite element method is used to study the postbuckling response of symmetric square laminates with a central cutout under uniaxial compression. The formulation is based on Mindlinʹs plate theory and von Karmanʹs assumptions to incorporate geometric nonlinearity. The governing finite element equations are solved using the Newton–Raphson method. For the purpose of analysis, laminates with circular and elliptical cutouts are considered with a view to examine the effect of cutout shape, size and the alignment of the elliptical cutout on the buckling and the first-ply failure loads of laminates. It is observed that these parameters have a substantial influence on the reserve strength which laminates may posses beyond buckling.