Fabrication of welded hybrid joints of aluminum alloys and polymer composites with significantly enhanced long-term reliability

The effect of thermal degradation on the welded hybrid joints of metal and polymer composites is insufficient, which seriously inhibits the engineering applications of the joints. In this study, robust hybrid joints of metal and polymer composites were fabricated by the combination of friction lap welding (FLW) and laser surface treatment for investigating the effect of accelerated aging on the joint properties. Results showed that the FLW hybrid joints without laser surface treatment exhibited 91% reduction in the tensile shear force (TSF) after 7 days of accelerated aging tests. In contrast, the FLW hybrid joints with suitable laser surface treatment exhibited only 26% reduction in TSF even after 35 days of accelerated aging tests. Fractures of the tensile specimens occurred across the composite plates rather than along the joint interface. The enhanced reliability of the hybrid joints was mainly attributed to (1) the formation of micro-mechanical interlocking between the polymer composites and aluminum alloy plate, and (2) the modification of the stress distribution along the joint interface.