Creasing instability of polydomain nematic elastomers in compression

Abstract

Polydomain liquid crystalline (nematic) elastomers exhibit unique mechanical properties such as soft elasticity, where the material largely deforms at nearly constant stress, due to microstructural evolution. In this paper, we numerically study the effect of such remarkable soft behavior on the surface instability of a half-space polydomain nematic elastomer, which is uniformly compressed parallel to the interface under a plane-strain condition. We compare the creasing instability of nematic elastomers with that of neo-Hookean elastomers by presenting bifurcation diagrams, stress and strain development in the elastomers, energy relaxation, and surface morphology at the creased state. Our results reveal that soft elasticity stabilizes nematic elastomers in plane-strain compression. Remarkably, the critical strain and stress at which the crease nucleates depend nonlinearly on the degree of anisotropy in nematic elastomers. Moreover, we find that the morphology of the creased surface in nematic elastomers exhibits the universal cusp shape previously observed in neo-Hookean elastomers.