Charakterisierung des spröden Risswachstums in Polyethylen-Rohrwerkstoffen mit beschleunigten Prüfmethoden

This paper reports the investigation of slow crack growth (SCG) in various polyethylene (PE) pipe resins using the Full Notch Creep Test (FNCT) and a new-developed method using cracked round bar (CRB) specimens subjected to cycling loading. Furthermore the influence of the age of the liquid detergent environment used in the FNCT on the testing times was studied. It was shown that with increasing age of the liquid detergent environment the times until failure in the FNCT raise as well. REM photos of fracture surfaces of FNCT- and CRB test specimens show a similar fibrillare structure. Despite the different mode of loading and the different testing temperatures, the failure mechanism is similar. With the results from both tests, material rankings have been established and compared. It was shown that the FNCT- and the CRB-method result in the same material ranking. Compared to the FNCT method, the testing times of fatigue tests on CRB test specimens, especially of new PE 100 materials can be reduced by more than the hundredfold. The CRB method therefore can be used to quickly estimate the quality of newly developed PE pipe resins.