The effects of fibre surface silanisation on silica fibre/phenolics composites produced by the resin transfer moulding (RTM) solution impregnation route were investigated. Diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy and micro-Wilhelmy method were used to evaluate the surface properties of silanised silica fibre. The interlaminar shear strength (ILSS) measurements and morphological observations of the silica fibre/phenolics composites were also performed. The interactions occurring between silica fibre and the components of phenolic resin solution affect the dynamic adsorption behaviour of phenolic resin onto fibre reinforcement. The competitive adsorption of ethanol as solvent onto silica fibre suppresses that of phenolic resin. Fibre surface silanisation by c-aminopropyl-triethoxysilane (c-APS), c-glycidoxypropyl-trimethoxysilane (c-GPS) and c-methacryloxypropyl-trimethoxysilane (c-MPS) leads to the improvement of mechanical interfacial properties of silica fibre/phenolics composites on one hand and decreases the inhomogeneities of resin distribution and mechanical interfacial properties at different regions of the RTM product on the other hand.

Silica fibre/phenolics composites produced by resin transfer moulding (RTM) solution impregnation technique are finding applications as aerospace structures. Typical phenolics contain solvent to facilitate injection and mould filling. It has been found that volatilisations of solvent and condensation polymerisation byproduct would cause void in cured composites, which is believed to affect the properties of the final product. In the present study, the role of solvent in the RTM impregnation process of silica fibre/phenolics composites was investigated. Experiments on wettability and flow were performed to evaluate the thermodynamical interaction on microscopic level occurring in fibre and resin system. Void content and interfacial strength were also examined. For the first time it has shown that the RTM process of silica fibre/phenolics composites is highly solvent dependent. Phenolics form distribution gradient in RTM mould with respect to isomeric composition under the effect of solvent, which results, to a varying extent, in the inhomogeneity of void content and thus interlaminar shear strength of the resulting product. The present work gives an insight into the role of organic solvent in RTM processing and this will help in choosing the best possible solvent for the solution impregnation system.