Correlation of temperature-dependent fracture behavior and thermo-mechanical behavior of a polypropylene pipe grade material under cyclic load

• Cracked round bar test effectively assesses failure behavior of polypropylene. • Fracture behavior observed at the glass transition temperature and below. • Two failure areas determined across a temperature range of −10 to 95 °C. • Loss factor correlates with changes in fracture behavior. The long-term performance of polypropylene (PP) is crucial for ensuring the reliability and safety of PP pressure and non-pressure pipes. One method that allows for an accelerated assessment of a material’s durability is the cyclic Cracked Round Bar (CRB) test, which was used to investigate the temperature-dependent fracture behavior of PP across a very broad temperature range of T = −10 °C to 95 °C including the glass transition of the material. Results are compared with tensile tests and dynamic mechanical analysis (DMA) to identify potential correlations between mechanical-, thermo-mechanical properties and the fracture behavior. Both failure mechanisms typical for pipe materials, the ductile Area I and quasi-brittle Area II as well as the transition knee point between these areas, could be examined at all investigated temperatures. Further analysis of crack opening displacement and hysteresis underlines this result. A key finding is the correlation between the applied stress intensity factor and corresponding cycle number of the knee point at a given temperature and the DMA-derived damping behavior tan δ of the material. These findings offer a novel approach to enhance the accuracy and efficiency of determining the fracture behavior across a wide temperature range. It highlights the role of temperature in fracture behavior determination and the hidden potential of the DMA method.