Analysis of stripe domains in nematic LCEs by means of a dynamic numerical framework

Abstract

Liquid crystal elastomers are a class of materials which shows unusual characteristics due to its dual nature, i.e. the orientational behavior of liquid crystals combined with the intrinsic features of elastomers. Apart from inhomogeneities, the mesogens, which are linked to the polymer chains in LCEs and are modeled as a unit nematic director, are oriented along a unique direction in case of a monodomain sample. Among other remarkable properties, LCEs exhibit a particular behavior under mechanical stretching, such as the semisoft elastic response and the onset of stripe domains in the originally monodomain sample under certain conditions. As observed in experiments, in a sample with stripe domains the mesogens of two adjacent stripes are rotated through the same angle but with opposite senses of rotation. We aim to reproduce the stripe domains in nematic LCEs under mechanical stretch and high strain rates by using a dynamic three-dimensional mixed finite element formulation, which is based on the usage of a mixed principle of virtual power, local drilling degrees of freedom for LCE-network and mesogens and frame-indifferent free energy density functions based on tensor invariants associated with the mixed fields.