Rapid crack propagation in polyethylene pipe : combined effect of strain rate and temperature on fracture toughness

The need to predict the mechanical behaviour of polymers is motivated by the increasing use of these materials in structural applications. In order to consider safety in the design of engineering components, the question of a criterion for rapid crack propagation has been investigated in a medium density polyethylene (MDPE) used to extrude pipes for gas distribution. Work on the strain rate–temperature equivalence (ε ↔ T) was performed to study the yield stress, σs, as a function of ε and T. A shifting procedure enabled a behavioural master curve, σs versus 1/(aTε) to be drawn, where aT is the shift factor. Both cracked-ring and Charpy specimens were tested to characterize the fracture toughness KIC(T) of the MDPE. The values of the KIC(T) based on linear elastic fracture mechanics are superposed to form a fracture toughness master curve: KIC versus 1/(aTε).