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In this study, we have developed a user element subroutine (UEL) using the commercial finite element software Abaqus to simulate the photomechanical coupling of these nematic elastomers subjected to mechanical stress and illumination. To model the photomechanical coupling using the finite element method, the minimisation of the free energy approach is implemented considering Corbett and Warners formulation

 [1] for polymeric network elastic behaviour and Maier-Saupe theory-based formulation

[2] for nematic liquid crystal behaviour. A system of linear equations with displacements, order-parameter and the alignment direction as primary variables is developed following the Rayleigh-Ritz and Newton-Raphsons method. The developed model is benchmarked by comparing the result of a 2D LCE sheet with the work of Bai and Bhattacharya [2]. Moreover, the developed UEL is then used to simulate the exotic behaviours of the LCE sheets discussed earlier. The developed framework can also be extended to simulate the coupled photomechanical response of LCEs with patterned/varying alignment distributions.

Keywords: Liquid crystal elastomers; User element; Finite element method; Photo-mechanics

References:

1. M. Warner and E.M. Terentjev, Liquid Crystal Elastomers, International Series of Monographs on

Physics. OUP Oxford, (2007).

2. Ruobing Bai and Kaushik Bhattacharya, Journal of the Mechanics and Physics of Solids, 144,

104115 (2020).