Dynamic characterization of compliant materials using an all-polymeric split Hopkinson bar

Abstract

ABSTRACT--The split Hopkinson bar is a reliable experimental technique for measuring high strain rate properties of highstrength materials. Attempts to apply the split Hopkinson bar in measurement on more compliant materials, such as plastics, rubbers and foams, suffer from limitations on the maximum achievable strain and from high noise-to-signal ratios. The present work introduces an all-polymeric split Hopkinson bar (APSHB) experiment, which overcomes these limitations. The proposed method uses polymeric pressure bars to achieve a closer impedance match between the pressure bars and the specimen materials, thus providing both a low noiseto-signal ratio data and a longer input pulse for higher maximum strain. The APSHB requires very careful data reduction procedures because of the viscoelastic behavior of the incident and transmitter pressure bars. High-quality stress-strain data for a variety of compliant materials, such as polycarbonate, polyurethane foam and styrofoam, are presented.

Dynamic behavior of gamma-irradiated polycarbonate

“…The increase in the strain rate from 1100s -1 to 2300s -1 , as expected, results in a higher mechanical dynamic strength of PCLIGHT polycarbonate, "as received" (non irradiated) and irradiated [18,19].…”

High Strain Rate Mechanics of Polymers: A Review

“…titanium, magnesium alloy or aluminum, or a polymer, e.g. polymethylmethacrylate (PMMA), PC, or nylon [77][78][79][80][81][82][83][84][85][86][87][88]. Low impedance metallic bars do not require any changes to the experimental apparatus or data reduction.…”

“…However, rubbers were some of the first materials to be characterized in split Hopkinson bar experiments [1,2], and more recently a number of authors have proposed techniques to address these difficulties through modifications to the Hopkinson bar or other similar systems [57,66]. These include pulse shaping [62], low impedance Hopkinson bar materials to increase the transmitted force [76,77,81,82,148] or use of more sensitive force gauges to directly measure the force at the specimen bar interface [62][63][64]. Longer Hopkinson bars may be used to increase the duration of the experiment [53], as can direct impact systems [149], in addition, if stress gauges are combined with optical measurements of specimen deformation, the experiment duration is no longer limited by wave overlapping in the bars and longer durations can be achieved [150].…”

Propagation of a stress wave through a virtual functionally graded foam

“…Sawas [26] acknowledged the limitations on high noise-to-signal ratio and low achievable strain when using metal incident and transmitter bars with complaint specimens like rubbers and foams due to the very high impedance mismatch and short rise time of the pulse wave. They introduced an all-polymeric Split Hopkinson Bar system to overcome these limitations.…”