Abstract In this study, the mechanical properties of nanosilica
particulate-reinforced epoxy composites with different
crosslinking densities were clarified experimentally to consider
the interaction effects between nano-particles and the
network structure in matrix resin. The matrices were prepared
by curing with an excessive mixture of diglycidyl ether
of bisphenol A type epoxy resin as the curing agent for the
stoichiometric condition. The volume fraction of the silica
particles with a median diameter of 240 nm was constantly
0.2 for every composite. The crosslinking densities and glass
transition temperatures of the neat epoxy resins were identified
from thermo-viscoelastic properties measured by
dynamic mechanical analysis. Elastic moduli and strengths
of the composites and the neat epoxy resins were measured
by three-point bending tests. The glass transition temperatures
of the neat epoxy resins decreased linearly as the
crosslinking densities decreased from the stoichiometric
condition. The glass transition temperatures of the composites
were reduced by adding the nano-silica particles. The
bending moduli of the composites in the glassy state could be
predicted by using a mixture law of the composites regardless
of the crosslinking densities and glass transition temperatures.
The bending strengths were found to be sensitive
to the crosslinking densities: they were both higher (for
composites with high crosslinking densities) and lower (for
composites with low crosslinking densities) than those ofthe neat epoxy resin. These results demonstrate that the
interaction between nano-particles and network structures
reduces the bending strengths, especially for low crosslinking
densities.