Failure loads prediction of composite laminates using a combined elastoplastic damage model

Based on the framework of continuum damage mechanics and plasticity theory, a combined elastoplastic damage model which takes into account the plasticity effects and material properties degradation due to damage development was developed. Based on the closest point projection return mapping algorithm, a strain-driven implicit integration algorithm for the model was developed to update stresses and solution dependent state variables. A tangent stiffness tensor consistent with the developed numerical algorithm was derived to ensure the computational efficiency of Newton-Raphson method in the finite element analysis. In order to alleviate mesh dependency of finite element analysis results, the "Crack Band Theory" was applied to regularize the softening branch of the material model. Also, in order to avoid premature abortion of numerical analysis using strain softening material models based on implicit procedures, a viscous regularization scheme was applied to the damage parameters. Accordingly, the regularized numerical consistent tangent tensor was derived. User-defined material subroutine UMAT containing the numerical integration algorithm was coded and implemented in finite element procedure Abaqus v6.14. The efficiency of the material constitutive model was demonstrated through progressive failure analysis of a V-notched AS4/3501-6 composite laminate, the mechanical behavior of which demonstrates significant plasticity effects. The predicted results agree well with the experimental data reported in the literature and the developed model outperforms other existing elastic-damage models in predicting the failure loads. The result shows that the combined elastoplastic damage model can predict the mechanical behavior of composite materials which exhibit pronounced plasticity effects with sufficient accuracy. The proposed approach provides an efficient method for composite component and structural design.