Polycarbonate (PC) and acrylonitrile butadiene stylene copolymer (ABS) are known as materials having relatively high impact resistance. Recently, polymer alloy of these two materials has been developed to attain higher impact resistance and has become to be used in various engineering products. However, toughening mechanisms of PC/ABS alloy are not still understood very well. In this study, impact fracture toughness of PC/ABS alloy was evaluated for several weight fractions of PC and ABS. Three-point bend specimens were fractured by a drop weight. The time variation of the dynamic stress intensity factor was evaluated and the critical value of the stress intensity at crack initiation was determined. Fracture surfaces were also observed by SEM. The higher fracture toughness has been obtained for the case that the ABS particles are distributed in PC matrix. ABS particles would play a similar role as the butadiene particles in ABS resin during fracture process, i.e., reduction of the stress triaxiality due to the formation of the voids.
