Jointing of CFRP/5083 Aluminum Alloy by Induction Brazing: Processing, Connecting Mechanism, and Fatigue Performance

Abstract

Carbon fiber reinforced polymer (CFRP) is widely used in the lightweight design of high-speed trains due to its high specific strength. In order to further reduce the weight of the high-speed train body, it is necessary to study the joining process and fatigue properties of CFRP/aluminum alloys (CFRP/Al) structure. In this work, the CFRP plate and 5083P-O aluminum plate were successfully connected by an induction brazing method. The optimum parameters of induction brazing were determined to be an induction temperature of 290 °C, a normal pressure of 200 kPa, and a holding time of 5 s. After the 5083 plate was pre-anodized, the tensile strength of the CFRP/5083 joint reached a maximum value of 176.5 MPa. The anodization process introduced more surface micro-structures on the 5083 plate, leading to a better wetting behavior between CFRP and oxide film. Meanwhile, a new chemical bond, Al-O-C, was also formed at the interface of the CFRP/5083 joint. The fatigue limit of the CFRP/5083 joint was calculated to be 71.68 MPa through high-cycle fatigue (HCF) testing. The fatigue cracks initiated from the interface of CFRP/oxide film, and then propagated to base metal. Finally, the oxide film was peeled off from the base metal under shear stress, which contributed to the fracture of the CFRP/5083 joint. The bonding strength between CFRP and 5083 aluminum alloy is far from the conventional welded joints. Therefore, feasible approaches should be proposed to obtain a more robust bonding between CFRP and aluminum alloy in the future.