A Feasibility Study on the Fatigue Testing of NBR and PUR in the Dynamic Mechanical Analysis for Damage Prediction

For damage prediction of dynamically stressed elastomers, state of the art complex component tests are performed to characterize the load cycle dependent material behavior. To reduce the testing effort, material tests are occasionally carried out on suitable specimen geometries. Nevertheless, the aim is to further simplify and standardize the test series. Dynamic mechanical analysis (DMA) is a measurement method that can dynamically stress small test geometries under variable temperatures and frequencies (0.1–100 Hz). The aim of this study is to investigate whether the fatigue behavior of elastomers can be mapped using standard DMA methods and whether the material derived characteristics can be used to predict damage. For this study, single stage dynamic tensile tests were performed at a constant temperature and frequency using the DMA on an acrylonitrile–butadiene rubber (NBR) and an elastomeric polyurethane (PUR). Dynamic tensile tests on paraboloid specimens are used as a reference. The fatigue behavior of elastomers can be reflected in a change in dynamic stiffness. This can be modelled using the reference dynamic tensile tests. In the DMA, the change in dynamic stiffness cannot be reproduced by conventional methods. The NBR and PUR stiffen and the damping of the PUR decreases. Due to the stiffening effects, damage criteria based on decrease in dynamic stiffness cannot be applied.