Fracture toughness characterization of a PC/ABS blend under different strain rates by various J-integral methods

Abstract

A published, nonconventional J-integral method, based on the hysteresis energy and the ASTM E813 methods, has been employed to test the fracture toughness of a polycarbonate (PC)/acrylonitrile-butadiene-styrene (ABS) blend. The critical J values (J(Ic)) at crosshead speeds ranging from 0.5 to 20 mm/min obtained from the hysteresis energy method are similar to 10 to 20% higher than those obtained from the E813-81 method and similar to 50 to 70% lower than those obtained from the E813-87 method. However, the hysteresis energy method results in comparable J(Ic) values with a modified ASTM E813-87 method when the 0.2 mm offset line is replaced with a 0.1 mm offset line. The critical displacements in terms of the onset of crack initiation, determined from the plots of hysteresis energy vs. displacement, hysteresis ratio vs. displacement, and the true crack growth length vs. displacement, are fairly close in value. This indicates the critical crack initiation and the corresponding J(Ic) obtained from this hysteresis energy method indeed represent the actual physical event of the onset of crack initiation.