Unraveling the Relevant Length and Time Scales of Elastomers in a High Strain Rate Test

This study uses a recently developed cavitation approach, laser-induced membrane expansion (LIME), to study the high strain rate mechanical properties of three elastomers: poly-(styrene-<i>b</i>-isoprene-<i>b</i>-styrene) (SIS), cross-linked linear polydimethylsiloxane (<i>l</i>PDMS), and cross-linked bottlebrush PDMS (<i>b</i>PDMS) with different network topologies. The cavitation event was modeled as a damped harmonic oscillator to quantify the shear modulus and dissipation of the elastomer as a function of strain rate. Interestingly, the high strain rate shear moduli obtained from LIME of the three elastomers were similar, whereas they had markedly different shear moduli measured under quasi-static conditions. The length of the elastically active polymer during the cavitation event was also calculated, which is an important parameter for understanding the amount of energy dissipated in this high strain rate test. The difference in fundamental polymer dynamics that results in different mechanical properties as measured at high versus low strain rates has important implications for designing polymer networks that store, release, and dissipate energy effectively during high-rate deformation events.