FATIGUE CUT GROWTH OF THERMOPLASTIC POLYURETHANES

A fatigue cut growth evaluation for thermoplastic polyurethanes is presented. The results from an experimental design study that included four different polyol types, the effect of the molecular weight of the polyol and three different urethane contents are discussed. The polycarbonate polyol showed the lowest fatigue cut growth resistance. The molecular weight of the TPUs is of key importance for dynamic fatigue applications. The crack length as a function of the number of cycles and the cut growth rate as a function of the tearing energy for selected TPUs are also shown. The fracture surface morphology of the failed samples showed two distinct morphologies, first, a flat featureless region with apparent fast cut growth and second, a rough wavelike region with apparent slow cut growth.