Effect of Crack Arrester on Fatigue Crack Growth in Foam Core Sandwich Panel under Mode II Type Loading

Abstract

Crack arresters were installed to suppress interfacial crack propagation between the skin and core of CFRP/foam core sandwich panels. The effect of the crack arrester on suppressing the propagation of a fatigue crack was investigated under mode II type loading using end notched flexure specimens. Specimens were made from carbon /epoxy fabric prepreg and a polymethacrylimide foam core. The energy release rate, calculated by FE analysis, showed a considerable reduction at the crack tip as the tip approached the crack arrester. Fatigue crack propagation tests were carried out using sandwich panel specimens containing the crack arrester. The crack propagation rate, da/dN, decreased with decreasing distance from the crack tip to the arrester edge. Thus, the suppression effect of the crack arrester was demonstrated experimentally. The net stress ratio at the crack tip is greater than the load ratio owing to the influence of the thermal residual stress during molding. The net stress ratio dependency of the crack propagation resistance was evaluated for the sandwich panel, and was compared with that for the solid CFRP laminate to investigate the driving force under fatigue loading.