Influences of hydrothermal aging on cracked metallic structure with composite patch

Abstract

Tensile test and fatigue test were performed on aluminum alloy plate containing double-side cracks without patch, aluminum alloy plate containing double-side cracks with glass fiber patch and aluminum alloy plate containing double-side cracks with glass fiber patch immersion in water for 40 days, then the failure mode, failure mechanism, fatigue crack propagation and carrying loading capability were analyzed. The influences of hydrothermal aging on mechanical property of cracked metallic structure with composite patch were assessed. The results show that the hydrothermal aging reduces the ability of composite patches to weaken the interference effect between fatigue cracks, the propagation length from crack of hydrothermal aged specimen is shorter than that of the specimen without hydrothermal aging. After bonding patch to single face of aluminum plate, the fatigue crack propagation rate along the direction of thickness of plate is slow, and the shorter the distance from crack to the patch is, the slower the speed is, so the hydrothermal aging decreases the efficiency of hindering fatigue crack propagation along the direction of thickness of plate. Due to the effect of hydrothermal aging, the recovery rate of carrying loading is decreased to 45%, while the fatigue crack propagation life is decreased to 63.7%. Hydrothermal environment causes the aging of adhesive, resulting in the decrease of cohesive load between aluminum and adhesive, leading to the fall off of composite patch, the failure mode of adhesive layer is changed from cohesive failure to interface failure.

Keywords

• hydrothermal aging
• composite material
• adhesively bonded repair
• tensile test
• fatigue crack propagation