Mechanical and functional properties of carbon nanotubes-high performance fibre hybrid composites

Two approaches have been considered to optimize specific properties of Fibre Reinforced Composites (FRP). Firstly, carbon nanotubes (CNT)-epoxy nanocomposites are applied directly onto the brittle glass fibre surface as ‘healing coatings’ to reduce the stress concentrations, thus improving the reinforcing efficiency in the composite. Secondly, while using CNT-epoxy as bulk matrix, the processing and fabrication of CNTs containing hybrid composites is considered through ‘prepregging’. The effects of CNT/epoxy nanocomposite coatings applied to the fibre surface on tensile strength of single glass fibres are evaluated at different gauge lengths. It is shown that 0.3wt% CNT/epoxy nanocomposite coating gives rise to a significant increase in tensile strength of the fibre for all gauge lengths, better than the neat epoxy coating. The changes in prevailing failure mechanisms influenced by the epoxy and nanocomposite coatings have been identified. Effects of CNT structure, morphology and dispersion characteristics affected by CNT content, on crack healing efficiencies are also evaluated. The crack healing efficiency is much higher for the fibres coated with straight, less entangled CNTs than those with highly entangled CNTs, indicating the CNT dispersion state in the coating played an important role. Prepregs of carbon fibre-reinforced polymer composites containing CNTs are produced based on a solvent-less prepregging process. This work provides the comprehensive evaluation of the processing and curing parameters affected by the incorporation of CNT in CFRP prepreg manufacturing. The viscosity difference between the epoxies with and without CNTs is reduced by employing a temperature slightly higher than ambient. Based on the findings obtained from the rheological studies, suitable processing parameters are chosen for lab-scale production of CFRP prepregs. The effects of surfactant-treated CNTs on cure behaviour of epoxy and CFRP prepreg are also evaluated. The interlaminar shear strength, torsional shear modulus and strength of the 0.5wt% CNT-CFRP increased by 12%, 18% and 25%, respectively, compared with the neat CFRP, an indication of the improved properties of the matrix material. The changes in the fracture mechanism occurring after addition of a higher CNT content are identified