Mechanical characterization of soft materials using high speed photography and split hopkinson pressure bar technique

Abstract

High-speed photography in conjunction with the viscoelastic Split Hopkinson Pressure Bar (SHPB) technique was used to study soft material behavior under dynamic loading conditions. The real-time strains recorded using high speed photography were also used for validating the existing viscoelastic SHPB model. Polyurethane, sculpturing clay, sorbothane and bologna were tested as examples of soft materials. The dynamic compressive strength of clay increased by 4 orders of magnitude compared to the static compressive strength. The dynamic strength of sorbothane increased by 3 orders of magnitude compared to the manufacturer specified static values. Only dynamic experiments, between strain rates of 2700 and 3700/sec, were performed on bologna. All the four materials showed very high strain-rate dependence. The tested materials showed similar stress-strain plots. Clay, Sorbothane and Bologna were very compliant up to 30 to 35% strains followed by a stiffer region where the stresses increased rapidly to the maximum values. The specimens were in stress equilibrium for significant time durations and specimen peak stresses where achieved during this period.