Free edge effect on the post failure behavior of composite laminates undertensile loading

It is necessary to understand the complete load response and failure mechan ism of composite laminates to enhance the full potential of composite mater ials. Progressive failure algorithm for the post failure behavior of compos ite laminates was developed in the present study such that the damaged laye r with many micro-cracks is replaced with an equivalent layer of degraded p roperties. Stresses and strains are calculated by the 3-D finite element me thod based on the generalized layerwise plate theory (GLPT) in order to con sider the local effect near the free edges. The types and size of damage in composite laminates are predicted in the failure analysis that consist of a set of failure criteria and property degradation models for each mode of failure. In the case of matrix cracking, the macroscopic stiffness reductio n model based on the shear-lag method is introduced to the finite element m ethod in order to consider nonlinear progressive reduction of stiffness at each strain level. In order to predict the failure load and the damage accu mulation accurately, the refined finite element model with 3-D stress field is used. The distribution of stress considering free edge effect is presen ted. The failure mechanism and ultimate failure loads of the cross-ply and quasi-isotropic laminates for different stacking sequences with the same th ickness are investigated.