Characterisation of the mechanical behaviour of a polyurethane elastomer based on indentation and tensile creep experiments

Abstract

This research focuses on the determination of the mechanical properties of a viscoelastic polyurethane material with 2 different measuring techniques on 2 different length scales. Instrumented Indentation Testing (IIT) was used to test the material on a micro scale while tensile creep experiments characterised the macro scale material behaviour. All experimental data were processed by means of a fitting procedure based on the standard linear solid material model. The experiments were performed with different loading rates and hold values. The developed fitting procedure proved to be applicable to analyse the experimental data on both length scales. FEM was used to coordinate the applied strains of both measuring techniques. A comparison between the results originating from the experiments with both techniques indicated a stiffer material response on the micro scale (up to 4x). The more complex strain field inside the material during indentation compared to the uniform tensile loading on macro scale is responsible for this large discrepancy. For this reason comparing the results of IIT with tensile creep results should be done with great care. © 2013 WIT Press.