Delamination and matrix cracking of cross-ply laminates due to a spherical indenter

An investigation was performed to study delamination growth induced by matrix cracks in cross-ply composites resulting from a spherical indenter. The major focus of the study was to understand fundamentally the damage mechanics in terms of matrix cracking and delamination growth, and interaction between them. A nonlinear three-dimensional finite element model based on an updated Lagrange formulation was developed during the investigation. An augmented Lagrangian method was utilized to model the delamination interface condition. A general contact node search algorithm was proposed which can handle complex contact conditions, such as arbitrary slippage and discontinuous curvature. The indentation resulting from the spherical rigid indenter was also modeled. Fracture mechanics was applied to determine the delamination propagation in three dimensions. The strain energy release rates were calculated by a crack-closure technique. The model was verified analytically and experimentally.