Making something out of nothing: Enhanced flaw tolerance and rupture resistance in elastomer–void “negative” composites

Elastomers often exhibit large stretchability but are not typically designed with robust energy dissipating mechanisms. As such, many elastomers are sensitive to the presence of flaws: cracks, notches, or any other features that cause inhomogeneous deformation significantly decrease the effective stretchability. To address this issue, we have dispersed voids into a silicone elastomer matrix, thereby creating a “negative” composite that provides increased fracture resistance and stretchability in pre-cut specimens while simultaneously decreasing the weight. Experiments and simulations show that the voids locally weaken the specimen, guiding the crack along a tortuous path that ultimately dissipates more energy. We investigate two geometries in pre-cut specimens (interconnected patterns of voids and randomly distributed discrete voids), each of which more than double the energy dissipated prior to complete rupture, as compared to that of the pristine elastomer. We also demonstrate that the energy dissipated during fracture increases with the volume fraction of the voids. Overall, this work demonstrates that voids can impart increased resistance to rupture in elastomers with flaws. Since additive manufacturing processes can readily introduce/pattern voids, we expect that applications of these elastomer–void​ “composites” will only increase going forward, as will the need to understand their mechanics.