Inelastic finite element analysis of fibre-reinforced composite laminates with damage

In this study, a method of finite element analysis is presented to examine the three-dimensional inelastic behaviour of fibre-reinforced composite lam inates with damage. The constitutive model for the characterization of mech anical responses of non-linear composite materials to damage that was propo sed recently by the authors is employed. The formulation of the elastic dam age stress-strain relationship in incremental form is first developed and t hen incorporated within the context of the displacement-based finite elemen t procedure. Solution of the non-linear equilibrium equations is obtained w ith the modified Newton-Raphson iteration technique. Numerical implementati on of the stress calculation is discussed in detail. Results predicted usin g the present finite element program for uniaxial off-axis tensile loading of unidirectional graphite/epoxy composite laminates show satisfactory agre ement with those obtained from experiments. Other results describing the de velopment of damage zones, the inelastic effect on stress distributions and material property variations due to damage in cross-ply laminated composit e structures are also examined and discussed.