Probabilistic strength based matrix crack evolution in multi-directional composite laminates

Matrix cracking is the first and most dominant mode of damage in laminated polymer composites resulting in significant stiffness degradation. In the past, matrix cracking has been quantified using crack density evolution with loading and correlating the crack densities with stiffness degradation of the laminate. In the present study, an analytical framework for matrix crack evolution for a general Multi-Directional (MD) symmetric laminate has been proposed using oblique coordinate based shear-lag analysis coupled with a probabilistic strength approach. The statistical parameters have been estimated from a master laminate. The ply-by-ply crack density evolution has also been simulated. The crack density evolution and associated stiffness degradation predictions have been compared to existing experimental values. The stiffness degradation trends closely match with experimental data and stiffness values estimated from current approach are conservative.