Comparison of the strength and energy absorption of adhesive-bonded with resistance spot-welded single-lap joints

In lightweight body-in-white design, joints must not only provide strength but also allow for ductility and sufficient energy absorption. In this study, Single Lap Joints (SLJs) made with adhesive bonding are compared experimentally with those joined by Resistance Spot Welding (RSW) in low-carbon steel sheets. The influence of overlap length (۱۵ and ۲۵ mm) and weld number (one or two spots) is examined. Tensile force–displacement tests, conducted at room temperature with a crosshead speed of ۱ mm/min, revealed that extending the overlap from ۱۵ to ۲۵ mm improved the peak load, final displacement, and fracture energy of the adhesive joints. Among the tested configurations, double spot welds (۲RSW) provided the greatest capacity and toughness.  However, adhesive joints with a ۲۵ mm overlap (AB۲۵) exhibited higher strength than single spot welds (۱RSW), while their ductility was comparable. The observed failure modes varied across the joint types. In resistance spot welds, failure occurred mainly through button pull-out, whereas adhesive joints exhibited a mixed adhesive–cohesive failure mode.  In contrast, the ۲RSW specimens displayed pull-out and necking sequences, reflecting load sharing between the weld nuggets. Overall, the findings suggest straightforward design guidelines. When maximum strength and energy absorption are required, two Spot Welds (۲RSW) are the best choice. On the other hand, AB۲۵ joints, with a ۲۵ mm overlap, provide higher strength than single Spot Welds (۱RSW).

کلیدواژه ها:

Adhesive bonding ، Resistance spot welding ، Single-lap joints ، Energy absorption ، Failure modes ، Automotive steels