2009 Volume 58 Issue 5 Pages 417-423
The effects of strain rate and temperature on compressive properties of a biodegradable plastic made from oil were examined. Stress-strain curves of the biodegradable plastic were measured over a wide range of strain rates from 10–5 s–1to 104 s–1, using a quasi-static compression testing machine and a split Hopkinson pressure bar (SHPB) system. The strain rate slightly affected Young's modulus and considerably increased yield stress. In addition, the effect of temperature on Young's modulus and flow stress was also examined in a range from 3°C to 61°C. Young's modulus and yield stress decreased with increasing temperature. Empirical equation of yield stress for each temperature was derived for the strain rates from 102 s–1 to 104 s–1. A master curve of yield stress, reduced to 24°C, was made using these empirical equations. The values of activation energies related to the α and β relaxation processes were respectively estimated from the master curve of yield stress and from the best fit of equations based on Ree-Eyring theory and Bauwens' treatment. Temperature measurement of specimens was also made using thermocouples during dynamic compression. The ratio of the temperature rise to the mechanical energy of plastic deformation was calculated at a strain rate of 660 s–1 and 820 s–1.
