Fracture mechanics and relaxation processes in polyvinyl chloride

Linear elastic fracture mechanics has been applied to investigate the strain rate sensitivity of polyvinyl chloride over a range of temperatures (−197 to +80°C). Three‐point bend tests have been carried out at two widely different strain rates; in “static” (slow bend) conditions and in a “dynamic” (impact) situation. A specially instrumented Charpy impact hammer has been used to analyse the record of transient loads. The fracture toughness results show a close relationship to the relaxation phenomena between −60 and +75 °C; it was observed that in this region the maximum toughness correlated with the maximum β‐relaxation. It was also found that, while in the region of low temperatures the material showed a considerable degree of strain rate sensitivity, at +50° the dynamic and static toughness were of the same order of magnitude; this behavior differs substantially from that observed in metals.