Ultrasonic welding of CF/PEEK composites: Influence of welding parameters on interfacial temperature profiles and mechanical properties

International audienceThis work focuses on ultrasonic (US) welding of CF/PEEK composite containing a PEI layer at the interface. Welding time, load and amplitude are defined as the welding parameters. The influence of each parameter is assessed by temperature measurement and mechanical tests on US welding specimens. 80-μm diameter thermocouples are integrated into the interfacial polymer layer for in-situ monitoring of the maximum temperature profile during the welding phase. Only welding time and welding load have an influence on both temperatures and lap shear strengths (LSS). The highest LSS are close to 50 MPa, and the temperature achieved in those cases is around 580◦C. Interfacial fractures occur in both PEI and PEEK. PEI-based fracture is mostly brittle whereas PEEK-based fracture is a competition between brittle and ductile fracture. Finally, a fracture within the PEI/PEEK blend can occur. Raman spectroscopy is effectively used to quantify the thickness of this blend zone, it is about 0.075 mm