J(0.2)-values by impact testing

A drop weight testing machine is described to measure the J(0.2)-values of polymers in impact within the frame work of fracture mechanics. By changing the weight of a piston falling from the same drop height on the specimen, the impact velocity is constant but the impact energy is varied. This princ iple of impact testing is applied to the three point bending test in non-li near fracture mechanics. The apparatus is additionally instrumented with a load cell and a displacement transducer to follow the energy transfer durin g impact deformation in more detail. It is shown that polyethylene with she ar yielding develops a strong self-stabilizing effect against crack propaga tion, which is less pronounced in ABS which deforms by crazing. (C) 1999 El sevier Science Ltd. All rights reserved.