The influence of hardener-to-epoxy ratio on the interfacial strength in glass fibre reinforced epoxy composites

This work seeks to develop a better understanding of the influence that the chemistry of an epoxy thermoset system has on the stress-transfer capability of the fibre-matrix interface. We discuss the correlation between the interfacial shear strength (IFSS) and the properties of the matrix such as glass transition temperature (Tg), storage modulus and linear coefficient of thermal expansion (LCTE). The results indicate that each is strongly dependent on the hardener-to-epoxy ratio and it was found that changes in IFSS can be related to changes in the thermomechanical properties of the matrix. From the results presented it is hypothesized that residual radial compressive stresses at the interface are influenced by the chemistry of the matrix system due to the changes in the properties of the matrix. The combination of these residual stresses with static friction may lead to a potential variation of the interfacial stress-transfer capability in glass-fibre reinforced epoxy composites.