Energy criterion for modelling damage evolution in cross-ply composite laminates

The energy dissipated in cross-ply laminates during loading–unloading loops is obtained from stress–strain curves for cross-ply laminates and used in an energy based approach to predict the development of matrix cracking. The dissipated energy is correlated to the crack density growth data recorded for a reference laminate. The critical strain energy release rate, Gc obtained in this way is increasing with the applied strain. This phenomenon reflects the statistical nature of Gc distribution in the 90-layer: the first cracks (lower strain) develop in positions with lower fracture toughness. The obtained Gc data are in a good agreement with fracture toughness data obtained using LEFM based “compliance calibration” model in which the stiffness change with increasing strain is used. Finally, the matrix cracking development is successfully simulated using in the LEFM model, the data for critical strain energy release rate and an earlier derived stiffness–crack density relationship. It has been demonstrated that knowing the laminates geometry and measuring the laminate stiffness reduction with strain or (alternatively measuring the dissipated energy) the damage evolution may be simulated, thus reducing the necessity for optical observations to validation only.