Abstract Scope |
A simplified friction spot joining (FSpJ) technique was developed to join AA5052 and short glass fiber reinforced polyphenylene sulfide (GF-PPS) sheets. The influence of material characteristics and process parameters on the joint structure and joint strength was systematically investigated. Comparisons between joints made using reinforced and unreinforced PPS, and between those using treated and untreated aluminum sheets were made, and drastically differences in joint strength were observed. The process parameters could be controlled so the temperature at the center of the bonding interface may exceed the melting temperature, but not reach the decomposition temperature of the PPS, resulting in a fused area of PPS at the bonding interface. The process parameters include plunge depth, rotation speed, and dwell time of the joining pin. A full factorial design of experiments and analysis of variance were carried out to understand the influence of surface condition and process parameters on the joining process and mechanical strength of such joints. A maximum peak load as high as 4426.5 N was obtained using an optimal set of process parameters, which was significantly higher than that obtained from joints made of untreated aluminum sheets and reinforced PPS (962.7 N), or that from joints made from surface-treated Al sheets, but unreinforced PPS (1800.3 N). Examination of microstructures and fracture surfaces of the joints revealed important information about FSpJ joints. During joining the aluminum sheet tends to bend downward and intrude into the PPS which deforms accordingly. The depth and size of such intrusion of the aluminum sheet increase with plunge depth and rotation speed. A microscopic serrated bonding interface at the faying interface was formed near the center of the bond, which yields a desirable bonding strength together with the macroscopic interlocking produced by the interpenetration of aluminum and GF-PPS. A large number of dimples and glass fibers around these dimples were observed in joints made using treated Al and GF-PPS around the center of the faying interface, which is beneficial to the mechanical strength. |