抄録
The influences of plane stress and plane strain on fracture toughness behavior and mechanism of thermoset epoxy resin with polyamine hardener were investigated using 3-point bending fracture toughness tests under various displacement rates (10^<-1>-10^3 mm/min) and thicknesses (4-10 mm). The critical stress intensity factor (K_<IQ>) decreased with increasing displacement rate and thickness, and became stable at high displacement rate (>10 mm/min) and high thickness (>7 mm). The blunting of crack due to a localized plastic deformation process, i. e. the formation of stretched zone and crazes, and the condition of plane stress were dominated mechanisms for thin specimens tested under low displacement rates, while brittle fracture and the condition of plane strain were dominated mechanisms for thick specimens tested under high displacement rates.
