Optimisation and analysis of the reinforcement effect of carbon nanotubes in a typical matrix system

The scope of this work is the analysis of the reinforcement effect of carbon nanotubes in typical matrix systems, such as epoxy resins. As is well known, efficient dispersion is critical in achieving adequate reinforcement. However, dispersion processes are also well known to degrade the nano-phase. Degradation is manifested as reduction in the aspect ratio as the nanotubes de-agglomerate and break at the same time. For the purpose of this study, multi-wall carbon nanotubes (MWCNTs) with typical length of 1 mu m and diameter of 10-15 nm were used for manufacturing MWCNTs/epoxy nano-composites. The inclusion content was 0.5 and 1 % w/w respectively, and dispersion was performed using a typical sonicator gun. The tensile and the fracture toughness properties of the specimens were initially assessed and subsequently optimized. The optimisation process resulted in spectacular improvement in toughness properties. Finally, the antagonistic mechanisms that govern the reinforcement efficient were analysed via the application of the Halpin-Tsai equations for the tensile properties and the distinct contributions of the mechanisms that dissipate energy and enhance toughness, such as the nanotube pull-out, the plastic void growth of the epoxy and the nanotube debonding energy. The de-agglomeration and the aspect ratio reduction were shown to adversely affect the nano-composite properties and create an optimization envelop, well predicted by the employed simple models.