Intralaminar Progressive Damage of General Configuration Laminated Composites

A new analytical model for progressive damage in form of matrix cracking in continuous fiber reinforced laminated composites is developed, where both aspects of degradation of thermo-elastic material properties as a function of damage quantity, and the initiation and increase of damage as a function of applied loading are addressed. The model is able to consider the effect of both membrane (in-plane extension and shear) and flexural (out-plane bending and twisting) deformation. Mixed I and II modes crack formation are taken into account, by extension of energy based fracture mechanics principles to the particular behavior of matrix crack formation and multiplication in laminated composites. The experimentally observed increase of material fracture toughness during the process of matrix crack multiplication in fiber reinforced laminates (material R-curve behavior) is attributed to crack fiber bridging, and is included into the analytical model. New model parameters describing the R-curve behavior are proposed, and their influence on the predicted progressive damage behavior is analyzed. By its fracture mechanics energy based formulation, the model is also able to predict the scale effects specific to damage initiation and progression in laminated composites (e.g., the dependence of the damage process on the ply thickness), which is not possible by using the traditional strength based criteria.