Stiffness Loss of Composite Laminates with Transverse Cracks under Mode I and Mode III Loading

In this paper, the stiffness loss of general composite laminates with transverse cracks under mixed-mode loading is analyzed. The effective stiffnesses of the laminates are assumed to be functions of the nonlinear internal state variables (ISVs), which are dependent on crack densities, ply constraints, and crack opening profiles. The ISV corresponding to Mode I cracking is obtained from a series of finite element analysis. The ISV corresponding to Mode III cracking can be related to the Mode I ISV by considering geometrical constraints arising from the layup, for a laminate under tensile loading. Theoretical predictions of stiffness loss of glass/epoxy and graphite/epoxy composite laminates with transverse cracks are compared with experimental data available from published sources, for crossply, angleply, and quasi-isotropic laminates. In addition, the model enables the contributions from respective modes to the overall stiffness reduction to be determined. Results of analyses have shown good and excellent agreement with published experimental data from other researchers.