A modified semi-soft model of liquid crystal elastomers: Application to elastic and viscoelastic responses

Liquid crystal elastomers (LCEs) are emerging actuating materials composed of polymer networks and liquid crystal mesogens. A plateau in the stress-strain curve of LCEs, typical of the semi-soft characteristics, is commonly observed. Although the classical semi-soft model based on compositional fluctuations intends to capture this feature, it does not accurately predict the stress plateau. Moreover, the extended viscoelastic models often lack quantitative comparisons between their theoretical predictions and experimental results. To address these limitations, we phenomenologically modify the semi-soft model, applying it to capture both of the elastic and viscoelastic responses of LCEs. The modified model is further implemented into finite element simulations and used to study intriguing inhomogeneous deformation of LCEs. We demonstrated robust predictions of our model by quantitatively comparing with experimental results.