Electromechanical coupling in ferroelectric materials is extended to include the electric quadrupole. Internal
lattice displacements are coupled to strain to calculate both the polarization and the quadrupole and to provide
general methods to describe both acoustic and optical material behavior. Electromechanical coupling of a
monodomain is first analyzed and followed by finite element phase field simulations of a 180° domain wall. A
comparison between explicit electrostrictive coupling and nonlinear geometric effects is given which illustrate that
phenomenological electrostriction gives exactly the same electromechanical coupling as obtained from introducing
an effective field within the electrostatic Lorentz force.
Liquid crystal polymer networks exhibit a large number of field-coupled mechanical characteristics including
light induced deformation, flexoelectricity, thermal shape memory, electrostriction, and chemically induced
deformation. Light induced deformation has received considerable attention recently due to its unique functionality
for morphing structure applications since light can be considered clean energy and electrodes and wiring are
not needed for actuation. Azobenzene liquid crystals that are synthesized within a glassy liquid crystal network
(LCN) in a main chain configuration are considered here under time-dependent deformation from light stimuli.
A photomechanical constitutive model, coupled with viscoelasticity of the host polymer network, is developed
and compared with light induced blocked stress measurements using a blue light emitting diode (LED). It is
shown that the rate of change of stress in the main chain azobenzene liquid crystal is strongly dependent on the
rate of change of the liquid crystal microstructure. Additional comparisons to side chain azobenzene LCNs is
modeled and compared with data in the literature which illustrates the importance of viscoelastic creep of the
polymer network.
Liquid crystal elastomers combine both liquid crystals and polymers, which gives rise to many fascinating
properties, such as unparalleled elastic anisotropy, photo-mechanics and flexoelectric behavior. The potential
applications for these materials widely range from wings for micro-air vehicles to reversible adhesion skins for
mobile climbing robots. However, significant challenges remain to understand the rich range of microstructure
evolution exibited by these materials. This paper presents a model for domain structure evolution within
the Ginzburg-Landau framework. The free energy consists of two parts: the distortion energy introduced by
Ericksen [1] and a Landau energy. The finite element method has been implemented to solve the governing
equations developed. Numerical examples are given to demonstrate the microstructure evolution.
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