Fracture mechanics concepts, stress fields, strain energy release rates, delamination initiation and growth criteria

Publisher Summary When two or more materials are combined to form a material with improved functionality, such a material is termed as a composite material. Composite materials usually exhibit the best qualities of their constituents and qualities that neither of the constituents possesses. One of the most common failure modes of composite structures is delamination between plies. Delamination is a crack that forms between adjacent plies. The plies on either side of the delamination can have different fiber orientations. A complete understanding of composite delamination requires an appreciation for the fundamental principles of fracture mechanics and how these principles have been extended from the original concepts developed for isotropic materials to include the anisotropy typically present in composite materials. These extensions include the complexities of oscillatory singularities that occur for interface cracks in anisotropic media, and how these singularities are resolved for delamination growth prediction. Full implementation of Interlaminar Fracture Mechanics [“ILFM―] in design requires development of composite delamination codes to calculate strain energy release rates and advancements in delamination growth criteria under mixed mode conditions for residual strength and life prediction.