Failure analysis of thick composite laminates with multi-scale modelling under G₁₃ out-of-plane shear loading

For strength analysis of thick composite laminate, a multi-scale model based on sub-laminate stiffness homogenizing and stress/strain decomposition was introduced, in which the shear nonlinearity was also considered. In this way, the thick laminate could be modelled at a sub-laminate level and the structural failure could be predicted at a ply level. A user-defined FORTRAN subroutine (VUMAT) was written to model the shear nonlinearity and intra-laminar failure, and the cohesive zone model was introduced to predict the delamination between two sub-laminates. The strength and structural response of G₁₃ out-of-plane shear test were predicted with both multi-scale linear and non-linear model. By comparison with the experimental results, it is found that the multi-scale linear model works well in predicting structural load capacity, but significantly differs from experimental results when predicting the global load-displacement response. For multi-scale non-linear model, both the failure mode and the load-displacement curve fit well with the experimental results.