The fracture toughness, bending strength and bending elastic modulus of the nano-silica particulate-reinforced epoxy composites with different crosslinking densities were investigated experimentally to consider the interaction effects between the nano-particles and the network structure in matrix resin on the mechanical properties. The composite materials were prepared by adding silica particles of 240 nm in diameter to the bisphenol A type epoxy resins with the particle volume fraction of 0.2. The matrix resins in the composites having different crosslinking densities were manufacturing by non-stoichiometric curing. The fracture toughness and the bending strength of the near-stoichiometrically cured composites were found to be improved with by adding the particles. At lower crosslinking density, the particles worked against the mechanical properties as defects in the matrix resins.
