Prediction of Delamination Growth and Opening Near Intersection of Transverse Matrix Cracks and Delamination

The use of advanced composite materials for cryogenic fuel tanks reduces the mass of the structure but microscopic damage can cause fuel leakage. The amount of leakage depends on the connectivity of the damage and crack opening displacements. In this paper, the damage growth and the opening near the intersection of transverse matrix cracks (TMC) and a delamination are discussed. Three-dimensional finite element analysis (FEA) was used to analyze cross-ply and angle-ply graphite/epoxy laminates. The strain energy release rates (SERR) along the delamination front were calculated based on the virtual crack closure technique. The strain energy release rate has a very large variation along the delamination front and is sensitive to a variety of geometric and load parameters. There is an extreme gradient of the strain energy release rate near the intersection of the delamination front and the TMC. Based on the SERR results, likely delamination shape and size for cross- and angle-ply laminates were determined. Prediction of the likely shape and size will help one to understand the conduit for leakage. The opening near the intersection of the TMC and the delamination was calculated. The effect of ply thickness on the SERR and the opening is also discussed.