Postbuckling strength of composite plate with a hole

Buckling and postbuckling behaviors were analyzed numerically and experimen tally for composite plates with a hole. In the finite element analysis, the updated Lagrangian formulation and the eight-node degenerated shell elemen t were used. For the progressive failure analysis, the maximum stress crite rion was applied to the average stress in each layer of all the finite elem ents and then stiffness and stress corresponding to the failure mode were r educed to zero for the failed layers of all the elements. In the experiment s, the shadow Moire technique was used to monitor the out-of-plane deformat ion. PVDF sensors were used to detect the events of internal damage. The ma jor finding was that when a plate has low bending stiffness in the axial di rection, the local instabilities caused a change of mode shapes in postbuck ling range. Experiments showed good agreement with the finite element resul ts in the buckling load and the postbuckling strength. The influence of hol e 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.