Numerical and Experimental Investigation of an Ultrasoft Elastomer Under Shock Wave Loading

Wearable sensors can be utilized to measure the strain or pressure response following a blast, in order to establish injury thresholds and analyze symptoms. To explore the potential of utilizing the material polydimethylsiloxane (PDMS) when fabricating wearable sensors for blast environments, it is essential to first investigate the dynamic response of ultra soft PDMS under shock wave loading. The choice of PDMS for use in wearable sensors stem from the flexible and low cost characteristic of this silicone elastomer. The mechanical properties of PDMS has been reported in the literature. However, limited data exists regarding the mechanical properties of ultra soft PDMS. In this study, the possibility of utilizing the ultra soft PDMS for wearable sensors in an extreme environment such as shock exposure was explored. An approach combining experimental and simulation methods was applied to study the dynamic behaviour of hemispherically-shaped PDMS samples, having a 50:1 or 80:1 ratio of base-to-curing agent. The PDMS samples were exposed to a shock wave created by a custom-built compression-driven shock tube. Digital image correlation (DIC) technique was applied to measure the deformation on the PDMS sample’s surface, following shock wave exposure. A finite element analysis was performed to predict the mechanical response of the PDMS sample under shock wave loading. The deformation field provided by the finite element simulation was validated with the measured results from the DIC experiments. The comparison of out-of-plane displacement, maximum principal strain, and shear strain on the sample surface for PDMS 50:1 and 80:1 were shown. The dynamic elastic modulus of PDMS 50:1 and 80:1 was provided and compared with the quasistatic elastic modulus. A new analytical model was presented in this study to predict the quasistatic elastic modulus of PDMS with different ratios. This study will add new understanding of an ultra soft material’s dynamic response under shock wave loading.