Dynamic behavior of polymers at high strain-rates based on split Hopkinson pressure bar tests

Dynamic behavior of polymers at high strain rates from 10¹ to 10⁴ s^-1 is frequently investigated by split Hopkinson pressure bar (SHPB) technique. It is found that the apparent strain-rate effect on the dynamic yield stress of polymers based on SHPB tests may include significant contributions from lateral confinement effects when the strain-rate is beyond a transition strain-rate. A methodology based on numerical SHPB tests and the constitutive equation without considering strain-rate effect is proposed to identify this transition strain rate. Experimentally-measured strain-rate dependence of the peak stress up to the transition strain rate is recommended for the determination of the strain-rate dependence of the polymer, which is subsequently implemented into a dynamic constitutive equation including strain-rate and temperature effects. This dynamic constitutive equation together with a kinetic friction model is used to simulate the SHPB tests in independent publications. Reasonably good agreements between numerical predictions and experimental results are observed for a range of polymers at strain rates below 10⁴ s^-1.