Interlaminar damage model for polymer matrix composites

A constitutive model for fiber-reinforced composite materials with damage and unrecoverable deformation, which for the first time accounts for interlaminar damage, is presented. The formulation is based on Continuous Damage Mechanics coupled with Classical Plasticity Theory in a consistent thermodynamic framework using internal state variables. In-plane damage and novel formulation of interlaminar damage are included in order to describe the main failure modes of laminates structures. A novel implementation of the constitutive model into a finite element formulation incorporating geometric nonlinearity is presented. The model uses a small number of adjustable parameters, which are identified from available experimental data. Comparisons with experimental data for composite laminates under torsion loading are shown to validate the model for interlaminar damage. Coupled material and geometrical nonlinear analysis with simultaneous in-plane and interlaminar damage is demonstrated. The effect of warping on interlaminar damage is shown to be significant.