胶层缺陷对胶接-拉铆搭接剪切接头力学性能影响研究

Effect of Defects in Adhesive Layer on the Mechanical Property of Hybrid Bond-Riveted Lap Shear Joint

近年来胶接-拉铆技术在载运工具和航空航天等领域得到了广泛应用,而大型结构连接部件的制备过程会不可避免地在胶层内部产生局部缺陷,进而影响接头服役性能。以胶接-拉铆单/双搭接接头为研究对象,通过在胶层区域设置不同形式的人工缺陷,模拟胶层制备过程中产生的胶层内部缺陷,研究其对胶铆接头搭接剪切力学性能的影响规律。以6061-T6铝合金为基底制备胶接-拉铆接头试件,考虑单、双搭接试件形式,胶层内部预先放置不同厚度、面积、形状、位置的聚四氟乙烯缺陷片,对固化后的接头进行准静态拉伸破坏试验,并采用宏观观测和扫描电镜分析胶层失效表面宏观和微观样貌,从而对胶层内部缺陷对其失效模式影响机理进行评价。试验结果表明,接头主要失效模式为内聚失效,胶层中缺陷的位置、面积、厚度会对接头失效载荷以及失效强度产生不同程度影响,而缺陷的形状对接头力学性能影响不大。无缺陷的双搭接试件胶层失效载荷是单搭接试件1.62倍,单搭接试件胶层失效强度是双搭接试件1.24倍。有圆形缺陷的双搭接试件失效载荷是单搭接试件2倍,而失效强度没有受较大影响。基于现有试验结果,可以为实际结构设计中含胶层缺陷胶铆复合接头失效强度提供有效评估方法。

Hybrid bond-riveted technique has been widely applied in vehicle and aerospace fields in recent years. However, the fabrication process of large structural component can inevitably introduce defects in the adhesive layer and thus affect the joint service performance. Different forms of artificial defects are introduced in adhesive layer of hybrid bond-riveted single and double lap joints, simulating defects in the adhesive layer during the manufacture process, to study the effect of local defect on the lap shear mechanical performance of hybrid joint. The hybrid bond-riveted single and double lap joints are manufactured with 6061-T6 aluminium alloy as the adherend, and the artificial defects using Teflon spacer with different thicknesses, areas, shapes and locations are placed in the inner region of the adhesive layer before adhesive curing. Quasi-static tensile testing is then conducted on the ready-cured hybrid joint, and macroscopic observation and scanning electron microscopy are used to analyse the failure modes on the failure surface. Experimental results reveal that the dominant failure mode in the adhesive layer is cohesive failure, and the location, area and thickness of introduced defects in the adhesive layer have different degrees of effect on the failure load as well as the failure strength of the joint, while negligible effect is found in the shape of the defect. The failure load of double lap joint without defects is 1.62 times than that of single lap, and the failure strength of the adhesive layer in single lap joint is 1.24 times than that of double lap. The failure load of double lap joint with circular defects is twice than that of single lap, while the failure strength is not significantly affected. Based on the experimental data, effective evaluation method on the failure strength of hybrid bond-riveted joint with defects can be provided for practical structural design.