Characterisation of the dynamic properties of polymeric materials using the SHPB technique

The dynamic mechanical properties of a polyisoprene elastomer, comprising of the dynamic stress-strain and compressional relaxation modulus, have been characterised by means of the split Hopkinson pressure bar (SHPB) technique at a range of temperatures. The SHPB technique employed involved the use of two identical long steel bars, known as the incident and transmitter pressure bars, between which a small solid disc of the polyisoprene rubber was sandwiched. A hardened steel spherical ball was fired from a mechanical launcher and caused to make collinear impact with the plane free end of the incident pressure bar via a small cylindrical anvil. The strain pulses generated and propagated down the pressure bar were incident on, reflected from and transmitted through the polyisoprene specimen. The pulses were monitored by PZT sensors and were used to derive the dynamic properties of the specimen. It is shown that the stress and compressional relaxation modulus characteristics of this elastomer show larger variations and attain higher values at low temperatures than at high temperatures.