Constitutive modeling of progressive damage in composite laminates

A procedure has been developed for simulating progressive damage in composite laminates using a combination of an accurate stress analysis technique and a quasicontinuum approximation of the damaged material. An improved laminate theory incorporating a layerwise deformation field has been used to model the composite laminate. State variable constitutive equations originally developed for polymeric materials have been modified in order to accurately account for the effects of damage on the nonlinear strain rate dependent deformation of polymer matrix composites. The present research effort takes a phenomenological (known as continuum damage mechanics or CDM) approach to model damage at the micromechanical level (in the matrix). The effective stiffness or compliance of the damaged solid is defined in terms of the actual damage state represented by a properly selected damage variable. The finite element model for nonlinear analysis of laminated shells is coupled with the micromechanics-based mechanistic model for modelling the initiation and evolution of damage and for predicting the effective composite properties.