TY - JOUR
T1 - Finite element modeling of viscoelastic liquid crystal elastomers
AU - Chehade, Ali El Hajj
AU - Shen, Beijun
AU - Yakacki, Chris M.
AU - Nguyen, Thao D.
AU - Govindjee, Sanjay
N1 - Publisher Copyright:
© 2024 The Authors. International Journal for Numerical Methods in Engineering published by John Wiley & Sons Ltd.
PY - 2024/8/30
Y1 - 2024/8/30
N2 - Liquid crystal elastomers (LCEs) are elastomeric networks with anisotropic monomers that reorient in response to applied loads, and in particular, thermomechanical loads. LCE complex microstructures translate into complex behaviors, such as soft elasticity, rate-dependency, and hysteresis. In this work, we develop a three-dimensional finite element implementation for monodomain LCEs, with the material modeled as a finite deformation viscoelastic network with a viscous director. The formulation is designed so that the director field can be modeled as an internal variable. Unique to this class of materials is that their deformation response function depends on the full deformation gradient and not just the right-stretch tensor. This results in the material tangent losing its ‘usual’ symmetry properties. Accordingly, this makes the use of a first Piola–Kirchhoff finite element formulation advantageous. We utilize this framework to examine a number of nuances associated with the simulation and design of LCE based systems. In particular, we investigate in some detail the importance of a careful characterization of an LCE's initial director field. Via simulations of separate tension and compression experiments, we highlight the possibility of incorrect predictions when even small perturbations to initial conditions occur. The simulations are also used to illustrate the goodness of the model in replicating simple and complex experimental results, including the first-of-their-kind buckling-like column compression and thick-walled balloon inflation simulations.
AB - Liquid crystal elastomers (LCEs) are elastomeric networks with anisotropic monomers that reorient in response to applied loads, and in particular, thermomechanical loads. LCE complex microstructures translate into complex behaviors, such as soft elasticity, rate-dependency, and hysteresis. In this work, we develop a three-dimensional finite element implementation for monodomain LCEs, with the material modeled as a finite deformation viscoelastic network with a viscous director. The formulation is designed so that the director field can be modeled as an internal variable. Unique to this class of materials is that their deformation response function depends on the full deformation gradient and not just the right-stretch tensor. This results in the material tangent losing its ‘usual’ symmetry properties. Accordingly, this makes the use of a first Piola–Kirchhoff finite element formulation advantageous. We utilize this framework to examine a number of nuances associated with the simulation and design of LCE based systems. In particular, we investigate in some detail the importance of a careful characterization of an LCE's initial director field. Via simulations of separate tension and compression experiments, we highlight the possibility of incorrect predictions when even small perturbations to initial conditions occur. The simulations are also used to illustrate the goodness of the model in replicating simple and complex experimental results, including the first-of-their-kind buckling-like column compression and thick-walled balloon inflation simulations.
KW - first Piola–Kirchhoff form
KW - inhomogeneous directors
KW - liquid crystal elastomer
KW - viscoelasticity
KW - viscous director
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U2 - 10.1002/nme.7510
DO - 10.1002/nme.7510
M3 - Article
AN - SCOPUS:85193629288
SN - 0029-5981
VL - 125
JO - International Journal for Numerical Methods in Engineering
JF - International Journal for Numerical Methods in Engineering
IS - 16
M1 - e7510
ER -