An investigation into the effects of damage on the stresses in a composite laminate

Abstract

A general constitutive framework based on continuum damage mechanics with constraints imposed by thermodynamics for composite laminates is presented. Several methods for the calculation of matrix crack and delamination damage variables at a given damage state are presented and compared. A methodology for the prediction of matrix crack and delamination damage variable evolution is developed and shown to have the ability to model experimental data for several cross-ply laminates. The damage effects are incorporated into the model by two tensor-valued internal state variables for both matrix cracking and delaminations, respectively. Adjacent damage dependent ply stresses are crucial in influencing the initiation and growth of delaminations in composite laminates. A new method for determining the damage dependent stresses in the adjacent plies is presented along with calculated stress changes due to matrix cracking and interply delaminations. Along with this stress calculation method, a general framework is formulated for the determination of delamination growth using fracture mechanics along with several methods for determining the energy release rate of delaminations.