Microstructure-enabled control of wrinkling in nematic elastomer sheets

TL;DR

This paper develops a theoretical and numerical framework to understand and control wrinkling in nematic elastomer sheets by leveraging microstructure formation, revealing how microstructure can suppress surface wrinkles under stress.

Contribution

It introduces a combined analytical and numerical approach to study microstructure and wrinkling in nematic elastomer sheets, showing how microstructure can be used to control wrinkling.

Findings

Microstructure forms at different stretches than wrinkles.

Microstructure is finer than wrinkles under relevant conditions.

Microstructure can suppress wrinkling by altering stress states.

Abstract

Nematic elastomers are rubbery solids which have liquid crystals incorporated into their polymer chains. These materials display many unusual mechanical properties, one such being the ability to form fine-scale microstructure. In this work, we explore the response of taut and appreciably stressed sheets made of nematic elastomer. Such sheets feature two potential instabilities -- the formation of fine-scale material microstructure and the formation of fine-scale wrinkles. We develop a theoretical framework to study these sheets that accounts for both instabilities, and we implement this framework numerically. Specifically, we show that these instabilities occur for distinct mesoscale stretches, and observe that microstructure is finer than wrinkles for physically relevant parameters. Therefore, we relax (i.e., implicitly but rigorously account for) the microstructure while we regularize (i.e., compute the details explicitly) the wrinkles. Using both analytical and numerical studies, we show that nematic elastomer sheets can suppress wrinkling by modifying the expected state of stress through the formation of microstructure.