One-step tool-assisted In-situ perforation and thermal clinching using thermoplastic composite rivets: Process development and joint performance

: Fiber-reinforced polymer composites are increasingly used in lightweight aerospace and automotive structures because of their high strength-to-weight ratios. However, conventional mechanical fastening still relies heavily on pre-drilling and metallic fasteners, which can introduce additional weight, hole-making defects, and material-compatibility issues. In this study, a one-step tool-assisted in-situ perforation and thermal clinching process was developed using a carbon fiber-reinforced poly(ether ether ketone) hollow rivet temporarily coupled with a removable diamond grinding drill. The drill enabled in-situ perforation of CFRP laminates and was completely withdrawn after thermal clinching, leaving only the composite rivet in the final joint. The CF/PEEK rivet blank was optimized at 400 °C and 8 MPa. For in-situ perforation, the 400-mesh diamond grinding drill at 4000 rpm produced the lowest net projected C-scan abnormal area within the investigated parameter window, with entry- and exit-side values of 311.6 mm 2 and 301.4 mm 2 , respectively. Thermal clinching at 420 °C and 1.0 MPa was selected as the optimal forming condition within the investigated parameter window. Using the optimized perforation and clinching parameters, the final CFRTP-S joint achieved a peak load of 4232 ± 89 N and a specific joint load of 7148 ± 245 N/g. Compared with aluminum blind rivets and TA2 titanium bolted joints, the proposed joint showed approximately 5.5-fold and 4.9-fold higher specific joint load, respectively. These results demonstrate that the proposed process provides a lightweight, metal-free, and process-integrated joining route for composite structures.