Modelling the interaction between matrix cracks and delamination damage in scaled quasi-isotropic specimens

A series of tensile tests on scaled quasi-isotropic laminates have been carried out and modelled using finite element analysis to predict failure. Observations during testing and examination of the failed test specimens showed significant influence of matrix cracking and delamination on the final failure. Initially the virtual crack closure technique (VCCT) was used to determine the applied load that would cause free edge delamination. Experimental results showed that failure occurred at loads lower than those predicted. Matrix cracks, observed in the testing, were introduced into the model and interface elements were used to model the delamination development. This approach gave good correlation to the behaviour observed in the tests. Even in the specimens apparently dominated by fibre failure, delamination was shown to be significant.