Fracture characteristics of the laser bonding joint between the aluminum alloy and the CFRTP with preset aluminum alloy sheet

This paper presents a method to improve the laser bonding joint strength between carbon fiber reinforced thermoplastic composite (CFRTP) and aluminum alloy (Al). In this method, the CFRTP with preset aluminum alloy sheet is attained by the compression molding method after the aluminum alloy sheet is preset between the polyetheretherketone (PEEK) and carbon cloth. The CFRTP with preset aluminum alloy sheet is connected to the aluminum alloy by laser heat source, and the maximum load of the joint can reach 4264 N. Microstructure and fracture surface morphology of joint are observed and analyzed. The results indicate that the interface of the preset aluminum alloy sheet and CFRTP reveals an extensive diffusion of elements compared with the interface of aluminum alloy and CFRTP due to the effect of hot pressing. The fracture failure mode of the lap structure between aluminum alloy and CFRTP is mixed fracture with adhesion fracture as the main component. The fracture position of preset aluminum alloy sheet and aluminum alloy lap structure is observed near the weld seam fusion line, and numerous dimples are found on the fracture surface of aluminum alloy. The increase in joint bonding force is mainly attributed to the collective effect of two lap structures; during the stretching process, the interface between aluminum alloy and CFRTP first undergoes fracture, and then, preset aluminum alloy sheet undergoes plastic fracture failure.