Large deformation analysis of spontaneous twist and contraction in nematic elastomer fibers with helical director

A cylindrical rubber fiber subject to a twist will also elongate: manifestation of Poynting’s effect in large strain elasticity. Here, we construct an analogous treatment for active actuated via axisymmetric pattern spontaneous distortion. We start by constructing exact large-deformation solution the equations elasticity such imposed and stretch, which reveals warping twisting cross section absent passive rubbers. then compute corresponding non-linear elastic energy, encompasses Poynting but is minimized finite stretch. In second half paper, apply these results understand twist-contraction actuation nematic elastomer fibers fabricated with director fields that encode helical patterns contraction on heating. first consider making constant angle respect local coordinate system (conical spiral curves) verify predicted twist, contraction, cross-section deformation elements. Second, realistic distributions experimentally reported cross-linking while simultaneously applying stretch twist. Counterintuitively, find maximum produced optimal during fabrication. Finally, illustrate spontaneously coil into spring-like shapes if ends are prevented from relative each other. Such twist–torsion coupling would allow us make tendril-like “soft-spring” actuator low force high linear stroke compared intrinsic itself.