Time-Dependent Fracture Characteristics in Polypropylene Film: Dependence of Fracture Toughness on Loading Rate and Creep Crack Growth Characteristics

摘要

Time-dependent fracture characteristics were studied in short term tests and in long term tests using the tensile centrally cracked film of polypropylene. The fracture toughnesses were obtained in short term tests at different crosshead rates to determine the dependence of fracture toughness on the loading rate. The creep crack growth rates were measured in long term tests under various stress levels at various temperatures. The experimental results of crack growth rate versus stress intensity factor indicate that there exists the region of minimum constant crack growth rate which occupies a substantial proportion of the creep rupture life. It is found that the constant creep crack growth rates are controlled by the stress-dependent Arrhenius thermally activated process.