Quantification and modelling of the fracture & fatigue performance of nanoparticle-modified epoxies

Adhesive bonding and composite materials are being used increasingly in major structural applications, including present and future aircraft design. The structural integrity of these materials and joints is critical and directly related to the toughness and fatigue resistance. Thermoset polymers form the basis of these materials, but are highly crosslinked and hence are very brittle. Indeed, already significant advances in the use of these materials in industries such as aerospace, automotive and electronics are limited by the poor toughness and fatigue resistance. A very successful route to improve the toughness is to add a combination of soft and hard particles, e.g. rubber and silica, to form a 'hybrid' material. However, conventionally these silica particles are tens of microns in diameter, and are are too large for use with infusion processes for the manufacture of fibre composites, as they are strained out of the resin by the fibres. Nanoparticles are suitable for infusion processes due to their size, which is small enough to allow them to flow between the fibres during infusion and prevent any straining. Further, low viscosity resin is essential for efficient infusion; and nanoparticles, unlike micron-sized particles, do not increase the viscosity of resin when suitably surface-treated. This project will quantify the effect of the addition of nanoparticles on the performance of rubber-toughened epoxy. A range of microstructures will be manufactured, and experimental studies will establish the effect of the different microstructures on the fracture and fatigue performance. These microstructures will be described and modelled. The models will be used to predict the toughness of the materials, and the results will be used to optimise the microstructure of the matrix material for a fibre composite. The optimised material will be manufactured, as both a bulk plate and as a fibre composite. The fracture and fatigue performance will be measured, and the results will be compared with the performance of current composite materials.