Appraisal of Strain Rate Sensitivity of Polypropylene Nanocomposites

Neat polypropylene (PP) and PP reinforced with nano clay platelets were tested at a fixed quasi-static strain rate on UTM and at corresponding limiting strain rates on SHPB (Split Hopkinson Pressure Bar). Enactment with minimum possible thickness of specimens cum maximum impact pressure on SHPB experiments is found important to set limiting strain rate. Combination of stress-strain responses of the material systems from both high strain rate impact and quasi-static loading is used to estimate the representative strain rate sensitivity index 'm' values: A new approach more justified than the trend of using strain rates limited the quasi-static range. Particular constant strain value of 0.0125 m/m and room temperature of 21±3 oC at which 'm' values are calculated were considered. The increase in weight fraction of nano-reinforcement was found to increase strain rate sensitivity index of PP to the level comparable with the lower bound of the range for superplastic alloys.