Thermoviscoelastic constitutive equation of PP/PA blends and its rate-temperature equivalence relation at high strain rates

By using Instron 1342 testing system and an improved SHPB technique, PP/PA blends were tested at a wide range of strain rates from 10-4 up to 103 s-1 and at a temperature range of 25~80 ℃. Their mechanical responses are shown to be sensitive both to the strain rate and temperature. Based on the experimental data of 113 blends at a wide range of strain rates from 10-4 up to 103 s-1 and at a temperature range of 25~80 ℃, it is shown that the mechanical behavior of this PP/PA blends can be described with ZWT thermoviscoelastic constitutive equation. The corresponding thermoviscoelastic parameters for 113 blends were obtained. The predicted theoretical results coincide quite well with the experimental data. The experimental results also reveal the time-temperature equivalence relation for PP/PA blends. Raising the temperature is equivalent to the increasing of time (the decreasing of strain rate). Conversely, decreasing the temperature is equivalent to the decreasing of time (the increasing of strain rate). Through introducing a dimensionless parameter Z=(d/dt)0exp(A/kT)/E, two characteristic parameters: strain rate=(d/dt) and temperature T are put together to this unified parameter Z. From experimental results, A/k was fitted, A/k=8.595 ℃, and a unified curve characterizing the-time temperature equivalence relation was obtained.