Sublaminate- or ply-level analysis of composites and strain energy release rates of end-notch and mixed-mode fracture specimens

The sublaminate or ply-level analysis of composite structures is presently undertaken by a computational procedure yielding the stresses in regions affected by delaminations, transverse cracks, and discontinuities that are related to material properties, geometries, and loads. Attention is given to layers or groups of layers that are immediately affected by flaws; these are analyzed as if they were homogeneous bodies in equilibrium, in isolation from the rest of the laminate. Computed stresses agree with those from a three-dimensional FEM analysis.