Carbon fibre composite joints co-cured by advanced PEEK/PPS meshes with outstanding fracture toughness

The investigation of advanced joining techniques for aerospace composites is critical to ensure the aviation safety and promote the production efficiency. In this study, plain-woven PEEK and PPS meshes were selected as joining agents for an aerospace carbon fibre/epoxy laminate upon a co-cure process. An atmospheric plasma treatment was applied to the PEEK/PPS meshes for surface functionalisation, aiming to promote the chemical bonds and interactions between the meshes and the composite during the co-curing stage. The fracture resistance of the joints subject to mode I (opening) and mode II (shearing) loading conditions were conducted at both of ambient and high temperatures, which revealed excellent fracture resistance of the specimens joined by both of the plain-woven PEEK/PPS meshes. In general, the PEEK-cured joints showed more prominent fracture performance than the PPS-cured joints. In comparison to the composite joints without meshes, the mode I fracture energies of the PEEK-cured joints at ambient (22 degrees C) temperature and high temperature (130 degrees C) were 151% and 67% higher, respectively and the mode II fracture energies were 429% and 419% higher, respectively. The excellent crack resistance of the joints co-cured by the meshes was resulted from considerable peeling and tearing damage of the plain-weaved PEEK/PPS fibres during the crack propagation stage, which led to significant energy dissipation.