Postbuckling strength of composite plate with a hole

Buckling and postbuckling behaviors were analyzed numerically and experimentally for composite plates with a hole. In the finite element analysis, the updated Lagrangian formulation and the eight-node degenerated shell element were used. For the progressive failure analysis, the maximum stress criterion was applied to the average stress in each layer of all the finite elements and then stiffness and stress corresponding to the failure mode were reduced to zero for the failed layers of all the elements. In the experiments, the shadow Moire technique was used to monitor the out-of-plane deformation. PVDF sensors were used to detect the events of internal damage. The major finding was that when a plate has low bending stiffness in the axial direction, the local instabilities caused a change of mode shapes in postbuckling range. Experiments showed good agreement with the finite element results in the buckling load and the postbuckling strength. The influence of hole sizes and stacking sequences was investigated on the compression behavior of the plate. The postbuckling strength was dominated by the value of the bending stiffness in the axial direction.