Fatigue Crack Propagation under Mixed Mode I and III in Polyoxymethelene Homopolymer

While mixed-mode loading conditions became hot topic recently, it is still quite unexplored area, even in case of metals. In case of polymers, this is even more complex problem, thanks to their higher sensitivity on higher temperatures connected with friction. Since polymer materials are very popular, this topic is of high interest. One of the best experimental specimens for achieving mixed mode loading conditions is the CRB specimen, as it provides clear mixed-mode I + III conditions under tension + torsion. Furthermore, for lifetime predictions it is necessary to calculate some material constants based on measured crack growth rates. However, these crack growth rates are not as easily and accurately measured on CRB specimens, as on CT specimens. Therefore, the main focus of this study is to observe difference between lifetime predictions based on CT and CRB data and possible application of CT data for CRB specimens.