Optimum selection of ply orientation in bonded repair under biaxial loading

Abstract

The effect of ply orientation on the performance of bonded repair technology applied to a cracked plate under biaxial loading is discussed. The application of fracture mechanics to the improvement of the structural integrity via the use of finite element analysis is highlighted. The patching concept involves closing up the crack opening displacement. Consequently, the stress intensity factors or the energy level near the crack tip can be reduced. Most efforts have been made on the study of how to optimize the patch fibre orientation at different biaxial loading ratios when a single- or double-sided reinforcement method is used. Two cases, the central crack and the cracked fastener hole, are analysed to show the interaction between biaxial loading and ply orientation that affects the patching functions. The results show that, for most cases, the stress intensity factors and thus the minimum strain energy density factor can be reduced to a minimum if the ply orientation is arranged to slightly coincide with the maximum principal tensile stress.