“湿热”老化对复合材料胶补金属结构力学特性的影响

Influences of hydrothermal aging on cracked metallic structure with composite patch

通过玻璃纤维复合材料补片对含穿透双边裂纹的铝合金板进行单面胶接修补,测试修补试件“湿热”(加温浸泡)老化实验前后力学性能,并与未修补试件进行对比,分析老化前后修补结构的破坏模式、失效机理,评估“湿热”老化对修补结构疲劳裂纹扩展寿命和承载能力的影响。结果表明:“湿热”老化降低了复合材料补片削弱疲劳裂纹之间干涉效果的能力,老化试件从裂纹的扩展长度小于未老化试件的;距离补片越近,沿金属板厚度方向疲劳裂纹扩展速率越慢,老化后复合材料补片减缓沿金属板厚度方向疲劳裂纹扩展速率的作用下降;老化严重削弱了修补结构承载能力恢复率和疲劳裂纹扩展寿命,老化试件的承载能力恢复率下降为未老化试件的 45%,疲劳裂纹扩展安全寿命下降为未老化试件的 63.7%;老化降低了胶层与金属之间的粘合力,造成了复合材料补片的提前脱落,胶层的破坏模式由内聚破坏转变为界面破坏。

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.