Quantitation of the reinforcement effect of silica nanoparticles in epoxy resins used in liquid composite moulding processes

Epoxy–silica nanocomposites are investigated for their suitability as a new type of matrix for fibre-reinforced polymers (FRP) using injection technology (LCM). The key focus is the determination of the processing characteristics of the nanocomposites. The silica nanoparticle content varies between 0 and 25 wt% for the high performance epoxy resin. Photon Cross Correlation Spectroscopy (PCCS) and Scanning Electron Microscopy (SEM) analysis performed on the liquid and cured epoxy–silica nanocomposites indicate a nearly homogeneous distribution of the nanoscaled silica in the epoxy matrix, even at rather high weight percentages. Depending on the silica content of the composite, its stiffness, strength and toughness can be increased significantly compared with neat resin. Moreover, resin shrinkage and the thermal expansion (CTE) can be significantly reduced and the thermal conductivity increased. Concomitant the glass transition temperature remains nearly constant. The initial viscosity of the resin increases slightly depending on the nanoparticle content, while the gel-time slightly decreases. The injectability of the nanocomposite for the purpose of lamination using the LCM technology is nearly unaffected. The optimum filler content is at approx. 25 wt% silica. Epoxy–silica nanocomposites are now proven to be a new high performance polymer matrix for FRP structures manufactured by the low cost LCM techniques.