Thermal residual stresses effects on fatigue crack growth of repaired panels bounded with various composite materials

Abstract

Thermal residual stresses, due to the curing cycle of the bonded composite patch affects the stress/strain states and the crack patching efficiency of the single-side repaired aluminum panels. In this study the thermal residual stresses that occur as a result of the thermal expansion coefficient mismatch between the patch and the underlying cracked aluminum panel are investigated. The fatigue crack-growth life and the crack-front configuration of centrally cracked aluminum panels in mode-I condition with various single-side repairs of glass/epoxy, graphite/epoxy and boron/epoxy composite patches are curried out. Sensitivity of the obtained residual stresses to different curing temperatures of the repaired panels with various composite patches is also investigated. It is shown that low curing temperatures (e.g., 60 °C) with long curing cycles have not a considerable effect on fatigue crack-growth life of the repaired panels with glass/epoxy patch and have minor effects for repaired panels with graphite/epoxy and boron/epoxy composite patches. It is also shown that considering the thermal residual stresses, the obtained FEM fatigue life and crack-front shapes of the repaired panels using glass/epoxy patch are in good agreement with those obtained from the experiments.