Fracture mechanics characterisation of effects of stabilisers on creep crack growth in polyethylene pipes

The failure behaviour of several polytheylene (PE) formulations has been characterised using linear elastic fracture mechanics (LEFM), creep crack growth (CCG) tests, and internal pressure testing. In total, six PE formulations (two polymer types with three stabiliser systems) were investigated. While no influence of stabiliser type was found in either type of polymer at high crack speeds, significant effects of the added stabiliser type and concentration were found for very low CCG rates. The experimental data also indicate good agreement between the test results of CCG experiments and the pressurised pipe tests (i.e. identical material ranking in both tests). This corroborates the hypothesis that the brittle or quasi-brittle failure of pressurised pipes can be predicted using a LEFM aproach and that CCG tests may be a useful experimental screening tool to evaluate stabiliser effectiveness.