Influence of process parameters on mechanical performance and bonding area of AA2024/carbon-fiber-reinforced poly(phenylene sulfide) friction spot single lap joints
Materials & design
Friction spot joining has been shown to be a potential technology to produce metal-composite hybrid joints. In this study, the effects of friction spot joining process parameters on the bonding area and mechanical performance of single lap joints were investigated using full-factorial design of experiments and analysis of variance. The main process parameters with significant influence on the bonding area were joining pressure, tool rotational speed and joining time. Joints with ultimate lap
... ith ultimate lap shear forces varying between 1698 ± 92 N and 2310 ± 155 N were obtained. Tool rotational speed and joining pressure displayed the highest influence on the lap shear strength of the joints followed by tool plunge depth, whereas the joining time was not statistically significant. The interaction between the rotational speed and joining time was the only interaction with a significant effect on the mechanical performance. Furthermore, the displacement at peak load and joint failure energy changed from 0.5 ± 0.0 mm to 0.8 ± 0.1 mm and 0.55 ± 0.04 to 0.97 ± 0.12 J, respectively, suggesting brittle fracture of the joints. In general, a larger bonding area as a result of higher heat input led to increased mechanical performance. The generated regression model by the analysis of variance was used to identify an optimized set of parameters for increasing the lap shear strength of the joints. Finally, it was demonstrated that higher heat input increased the amount of voids and defects in the joints because of the higher amount of entrapped air in the low viscosity molten polymer, as well as the large difference in the shrinkage properties of the matrix and carbon fibers. However, no correlation was observed between the area fraction of the voids and mechanical performance because the strength of the joints is dominated by the bonding area. Furthermore, the process temperature was monitored, which varied in the range of 370°C to 474°C.