Multifunctional Carbon Fibre Reinforced Hierarchical Composites based on Vertical Graphene

Abstract

Carbon fibre reinforced polymer (CFRP) is becoming increasingly popular in various areas owing to its high strength to weight ratio and high resistance to corrosion compared with metal rivals. However, there are also some drawbacks, such as poor resistance to crack propagation, low electrical and thermal conductivity in thickness direction, which are dominated by the inherent nature of interface and matrix in composites. These drawbacks limited the wider application of CFRP, while developing multifunctional composite is a good solution to these issues. The additive nature of the manufacturing processes of CFRP makes it possible to introduce other functionalities, such as improved strength, improved electrical conductivity, and energy storage capability. This thesis aims to develop carbon fibre (CF) reinforced multifunctional composites by combining CFs with vertical graphene (VG). Such a combination can improve the mechanical and electrical properties of CFRP and create a platform for the introduction of other nanomaterials, such as silver nanowires (AgNWs) and manganese dioxides (MnO2) nanoflowers, to develop multifunctional composites. Firstly, VGs were deposited onto CFs through a plasma enhanced chemical vapor deposition. Multiple characterizations were then conducted on the resulted VG modified CFs. These results showed that VGs grafted on the CF dramatically increased the surface roughness and surface wettability. The interfacial shear strength between CF and epoxy matrix was enhanced without significant tensile strength degradation on CF. Next, conductive AgNWs were added into epoxy matrix and combined with VG modified CFs to improve the electrical conductivity of composites, which has potential application in the lightning strike protection of composite structures. Then, MnO2 nanoflowers were introduced onto the VG modified CFs through an electrochemical deposition process and enabled the CFs with energy storage capability. A structural supercapacitor was developed as an example of multifunctional composites with VG&MnO2 modified CF electrodes and polymer electrolyte. Lastly, aiming at the poor cycling stability of MnO2 modified CF electrode, a multilayer electrode structure was developed to achieve the long-term cycling stability. In achieving these, important scientific contributions are made to the developing methods of multifunctional CF reinforced composites, which broad the application of CFRP and enable the further lightweight design of CFRP in the future