Dynamic Strength of PDMS-Based Elastomers under Combined Pressure-and-Shear Impact Loading

Filled elastomers are used in a variety of engineering applications from structural supports to impact mitigation protection. In rubbery elastomers, such as cross-linked polydimethylsiloxane (PDMS), silica and quartz fillers have been used to provide improved mechanical and creep properties. To-date, the strength of these materials at high strain rates and high pressures is poorly understood. In the present study, high-strain-rate pressure-shear plate impact (PSPI) experiments have been conducted to investigate the dynamic strength of two commercially available silicone elastomers, DC745U and Sylgard 184, the former containing a high filler content and the latter being unfilled. The goal is to better understand the effects of pressure, strain hardening, and strain rate sensitivity on their strength. The pressure range investigated is 0.75 to 3.6 GPa at shear strain rates up to 7x10⁵/s. The flow stresses in both elastomers are observed to be highly pressure sensitive with the shear strengths of DC745U and Sylgard reaching 350 MPa and 280 MPa, respectively, at pressures ~ 3.6 GPa. Both elastomers show considerable strain hardening, the effect of which increases with increasing pressures. In contrast to the observed pressure and strain sensitivity, the strength appears nearly insensitive to strain rate within the pressure range investigated.