Mechanical properties of fibrous liquid crystal elastomers

Abstract

This paper presents a systematic investigation into the mechanical behavior of photosensitive liquid crystal elastomer (LCE) fibers, with an emphasis on addressing the insufficient consideration of viscoelastic effects in existing theoretical models. A constitutive model for LCEs incorporating both hyperelasticity and viscoelasticity is established. Specifically, a quadratic polynomial hyperelastic model is employed to describe the nonlinear elastic response at different temperatures, while the Prony series and the Williams–Landel–Ferry (WLF) temperature shift function are utilized to characterize the temperature-dependent viscoelastic relaxation behavior. Experimentally, quasi-static uniaxial tension and stress relaxation tests are conducted using a UTM T150 micro-nano tensile tester, yielding stress–strain curves and relaxation modulus curves at various temperatures, from which the model parameters are determined via fitting. The results demonstrate that the proposed model satisfactorily describes the passive deformation behavior of LCE fibers under the combined action of hyperelasticity and viscoelasticity, with numerical simulations showing good agreement with experimental data. This study provides a theoretical foundation for the quantitative analysis and design of LCE fibers in fields such as soft robotics.