Effects of gauge length and strain rate on fracture toughness of olyethylene Terephthalate Glycol (PETG) film using the essential work of fracture analysis

Essential Work of Fracture (EWF) analysis was used to study the fracture toughness of a PETG film. In the study of the gauge length (Z) effect on the specific essential work (w_e) using Z = 50, 100, 150, 200 and 250 mm, it is observed that w_e is independent of gauge length, except that a slightly lower w_e value was measured for Z = 50 mm. Interestingly, for specimens with long gauge lengths (Z ≥ 150 mm in this study), brittle fracture occurred. The minimum ligament length at which ductile/brittle transition took place was observed to decrease with increasing gauge length. There is a small strain rate effect on w_e with loading rates less than 1 mm/min. But with higher loading rates, w_e showed no strain rate sensitivity.