Modelling damage evolution in laminated composites using cohesive zone models

One of the most difficult problems in designing composite structures is to ensure tolerance of severe damage. Current practice requires significant, time-consuming, and expensive testing to establish damage tolerance certification. In this study we shall discuss the application of cohesive zone modelling approach for analyzing the damage tolerance of laminated composites with or without the existence of stress concentrators. A 3D, mode-dependent cohesive zone model (CZM) is incorporated through the use of cohesive elements, which allow tractions to persist across displacement discontinuities (cracks or strain localizations), which arise after the attainment of a local failure condition. An essential feature of the formulation is that the existence and shapes of major crack systems need not be prescribed a priori. Successful applications will be reported to some practical problems in composite engineering, which cannot be adequately analyzed by conventional tools such as LEFM. It will be shown that the CZM simulations can successfully reproduce experimentally measured crack shapes that have been reported in the literature.