From diffuse damage to discrete crack: A coupled failure model for multi-stage progressive damage of composites

The multi-stage failure process and the coupled failure mechanisms have posed great challenges to damage analyses of fibre-reinforced composite laminates. In this study, a coupled failure model (CFM) is proposed which incorporates both smeared crack model (SCM) and discrete crack model (DCM) through an energy-consistent thermodynamic framework. While SCM is well suited for describing crack nucleation and diffuse damage at initial failure stage, DCM offers a great tool to model the subsequent crack growth and its interaction with other failure modes. A hybrid SCM/DCM formulation is developed for CFM, so that the progressive failure process from diffuse damage to propagation of major cracks is characterized. Furthermore, inherent limitations of each standalone model, such as convergence difficulty and computational inefficiency, are effectively resolved by the proposed approach. Performance of CFM is demonstrated through a few numerical examples, including element validation, Off-axis tensile and open-hole tension tests of composite laminates.