Low-temperature plasma assisted growth of vertical graphene for enhancing carbon fibre/epoxy interfacial strength

The interfacial interaction between fibres and polymer matrix is critical to the mechanical and functional properties of fibre-reinforced composites. In this work vertical graphene (VG) is directly grown on carbon fibres using plasma-enhanced chemical vapour deposition (PECVD) operating at a relatively low-temperature around 400 °C. The VG height is controlled via plasma density that can be controlled by adjusting the distance between the substrate and plasma centre. The effects of VG with different heights on fibre surface roughness, wettability, tensile strength, and interfacial shear strength between carbon fibre and epoxy are investigated. Our results show that grafting VG at 400 °C does not degrade the mechanical strength of the carbon fibres; instead, it improves the interfacial shear strength between the carbon fibre and the epoxy, with the maximum increase in IFSS of ~118.7% at a VG height of ~4.2 μm. This increase can be attributed to the greatly improved surface roughness and the reinforcement effect of vertical graphene surrounding the fibres. The research demonstrates the potential of grafting VG on carbon fibres in improving the mechanical properties of carbon fibre reinforced composites and developing multifunctional hierarchical carbon fibre reinforced composites.