Characterisation of the impact behaviour of polymer thermoplastics

One of the most important features when predicting the impact response of plastic components is the characterisation of the material in impact conditions. In this work, a new method to obtain stress/strain curves of thermoplastics at constant strain-rates is proposed. Instrumented tensile-impact tests have been performed on polypropylene samples at different impact energies. The use of tensile-impact techniques avoids some problems associated with flexural impact tests, and permits to determine the stress/strain curves and the strain-rate dependence of thermoplastics' behaviour in impact conditions. The results show that in the range of strain-rates analysed, polypropylene has an elastic-plastic behaviour with a slight plastic strain hardening. The isostrain-rate stress/strain curves can be used as material data in finite element simulations of impact events.