Effect of particle size on fracture toughness of epoxy resin filled with angular-shaped silica

Abstract

The effect of particle size on the fracture behaviour of cured epoxy resin filled with angular-shaped silica was studied. Angular-shaped silica particles were prepared by crushing fused natural raw silica and were classified into six groups with different mean sizes ranging from 2 to 47 μm. Critical stress intensity factor ( K c) and critical strain energy release rate ( G c) of the cured epoxy resin filled with these silica particles were measured. Both K c and G c values increased with an increase in particle size of the silica. Scanning electron microscopic observations of crack tips and fractured surfaces showed that the damage zone was formed at the crack tip by particle fracture and by crack diverging. This phenomenon became more pronounced with increase in the particle size. The higher K c and G c values appear to be derived from the dispersion of the stress concentrated at the crack tip due to the crack diverging and from energy absorption due to the formation of a damage zone.