Experimental and numerical investigation into strength of bolted, bonded and hybrid single lap joints: Effects of adherend material type and thickness

In line with the developments in advanced engineering applications such as aerospace and automotive industries, the techniques of joining similar and dissimilar materials have become a crucial issue, i.e. the need for a stronger joint has significantly grown. Compared to conventionally used bolted, riveted and pinned joints, adhesively bonded joints have been increasingly used due to its improved fatigue life and damage tolerance and lower structural weight, especially the case when relatively thin adherends are used. Alternatively, hybrid joints, combination of two or more joining techniques, are presently investigated to create a joint with higher strength than those gained from one technique. In this study, we compared mechanical performance of bolted, bonded and hybrid single lap joints subjected to the tensile loading using three different adherend thicknesses and two different adherend materials with different mechanical behaviors, such as yield and tensile strength and ductility. To this end, a combined experimental and numerical study was performed. In finite element simulations, cohesive zone, ductile and shear damage models were used to model the damage initiation and evolution for the adhesive film layer (AF163-2K), aluminium adherend (AL6061 and AL7075) and the steel bolt materials, respectively. Force displacement curves, the amount of energy absorbed and failure history for each configuration tested, were analysed extensively to elucidate the strength of various joints.