The development of high performance hybrid joints between epoxy composites and PEEK/PPS composites: The mode-II and mix mode-I/II fracture behaviour

The development of effective methods for the bonding of Poly-etherether-ketone (PEEK) and Polyphenylenesulphide (PPS) composites to thermoset composites is appealing to expand their applications in aerospace industry. Herein, the surfaces of PEEK and PPS composites were treated by a high-power UV-irradiation technique for 6 s, that proved to significantly improve their intrinsically low surface activities. Carbon fibre reinforced epoxy composites were then directly cured onto the PEEK and PPS composites with or without an aerospace film adhesive at the joining interfaces. The mode-II and mix mode-I/II fracture behaviour of the hybrid joints were studied using an end notched flexural test and a fixed-ratio mixed-mode test, respectively. It was observed that the failure of the hybrid joints without adhesives mainly took place at the joining interfaces. In this case, the lack of resins at the fracture plane resulted in relatively low fracture toughness. Encouragingly, a cohesive failure was observed for the hybrid joints with adhesives in all the cases, owing to the enhanced adhesion between the adhesive and the PEEK/PPS composites upon the UV-treatment. This phenomenon indicated that optimal fracture resistance of the hybrid adhesive joints was obtained for the given material systems.

Automated summary

The bonding of PEEK and PPS composites to thermoset composites was improved by treating their surfaces with high-power UV-irradiation. The adhesive joints showed enhanced fracture resistance and cohesive failure at the joining interfaces, indicating the effectiveness of the UV-treatment in improving adhesion.