Deformation localisation in stretched liquid crystal elastomers

Poudel, Rabin, Sengul Tezel, Yasemin and Mihai, L. Angela ORCID: https://orcid.org/0000-0003-0863-3729 2024. Deformation localisation in stretched liquid crystal elastomers. Mechanics of Soft Materials 6 , 8. 10.1007/s42558-024-00063-2

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Abstract

We model within the framework of finite elasticity two inherent instabilities observed in liquid crystal elastomers under uniaxial tension. First is necking, which occurs when a material sample suddenly elongates more in a small region where it appears narrower than the rest of the sample. Second is shear striping, which forms when the in-plane director rotates gradually to realign and become parallel with the applied force. These phenomena are due to the liquid crystal molecules rotating freely under mechanical loads. To capture necking, we assume that the uniaxial order parameter increases with tensile stretch, as reported experimentally during polydomain-monodomain transition. To account for shear striping, we maintain the uniaxial order parameter fixed, as suggested by experiments. Our finite element simulations capture well these phenomena. As necking in liquid crystal elastomers has not been satisfactorily modelled before, our theoretical and numerical findings related to this effect can be of wide interest. Shear striping has been well studied, yet our computed examples also show how optimal stripe width increases with the nematic penetration depth measuring the competition between the Frank elasticity of liquid crystals and polymer elasticity. Although known theoretically, this result has not been confirmed numerically by previous nonlinear elastic models.

Item Type:	Article
Date Type:	Published Online
Status:	Published
Schools:	Mathematics
Publisher:	Springer
ISSN:	2524-5600
Date of First Compliant Deposit:	1 October 2024
Date of Acceptance:	1 October 2024
Last Modified:	06 Nov 2024 11:06
URI:	https://orca.cardiff.ac.uk/id/eprint/172509

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