Thermally induced self-rupture of a constrained liquid crystal elastomer

Abstract

Liquid crystal elastomer (LCE) is a promising soft material which exhibits large actuation and can respond to different external fields with proper modifications. In the case of thermally actuated LCEs, the fracture properties are crucial to ensure that LCEs can robustly function under different loading and heating conditions, without unexpected failure. In this work, we systematically characterize the fracture energy of LCE at different temperatures and loading rates. We found that LCE behaves like a tough elastomer at low temperatures and high loading rates, but the fracture energy dramatically drops once LCE is heated beyond the nematic to isotropic transition temperature (TNI). At high temperatures, a constrained precut LCE sample can undergo self-rupture due to the large actuation stress. We have also used the measured fracture energy to successfully predict the critical temperature of self-rupture for different sample geometries.