Effect of strain rate on the fracture toughness of some ductile polymers using the essential work of fracture (EWF) approach

The plane strain fracture toughness of two ductile polymers, ultra high molecular weight polyethylene (UHMWPE) and acrylonitrile-butadiene-styrene (ABS), was measured by using the essential work of fracture approach. Truly plane strain fracture toughness (w_Ie) was measured for ABS at quasi-static and impact rates of loading. For UHMWPE, the measured values were only `near' plane strain values (w_Ie*). It was confirmed both w_Ie* and w_Ie were independent of specimen type but dependent on strain rate. For UHMWPE, there was a negative strain rate effect, i.e., w_Ie* decreased with increasing loading rate. At low quasi-static loading rate (v≤10 mm/min), w_Ie* was constant at 55 kJ/m². It then decreased to 15 kJ/m² when the loading rate was increased to 100 mm/min, and remained at that value even up to impact rate of loading (v = 3.7 m/s). For ABS, a mild positive strain rate effect was observed. W_Ie increased from 13 kJ/m² at v = 10 mm/min to 17 kJ/m² at v = 3.7 m/s.