A non-linear finite element approach for the analysis of mode-I free edge delamination in composites

Free edge delamination of uniaxially stressed layered specimens is simulated using non-linear finite element analysis. Generalized plane strain elements and interface elements have been developed for this purpose. Thermal and hygroscopic effects have been taken into account for the modelling of the plys, and a mode-I fracture model which incorporates strain softening has been used for the interface behaviour. The out-of-plane loading is controlled via an indirect displacement control technique, which permits tracing the entire loading history. Using non-linear finite element analysis free edge delamination in different graphite/epoxy laminates is examined. The numerical results are in good agreement with experimental evidence and do not suffer from spurious mesh dependence. Also the effects of laminate thickness (size effect) can be described properly.