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The liquid crystal elastomer is a liquid crystal polymer cross-linked to form a soft material. It also has a high elastomer superelastic and special physical properties of the liquid crystal, its mechanical behavior is complex and rich, showing the heat - stress - sequence mutual coupling characteristics of anisotropic and soft elastic. Especially since 2001, successfully prepared a new type of light-sensitive liquid crystal elastomers, large deformation occurs in the light, or even light-induced bending, is expected to be made of tiny light sensors and actuators. This paper will photosensitive liquid crystal elastomers constitutive features and light-induced bending study and simulation. Firstly, assume that the total energy of the liquid crystal elastomer deformation gradient sequence tensor, as well as a function of temperature. Constitutive equation continuum mechanics, completely in the framework of the tensor derived liquid crystal elastomer stress, entropy, and the equilibrium conditions of the order tensor. Neo-Hooke elastic anisotropic take the total energy and the Landau-de Gennes nematic phase free energy and to give specific expression of the constitutive equation. And resistant rubber with special symmetry to the liquid crystal elastomers such, we define an equivalent left Cauchy-Green tensor to describe the deformation, also by introducing a metric tensor to connect the macroscopic deformation scale micro-scale sequence. The results showed that, when not consider the role of the internal force even symmetric Cauchy stress tensor can be obtained with the metric tensor, it is equivalent to the left Cauchy-Green tensor coaxial. Deviatoric stress tensor will change the degree of order and biaxial. We further analyzed the configuration under zero stress. When the temperature changes, the LCD high-elastic experience spontaneous deformation; constant temperature, the director can also zero stress to rotate freely, showing the soft elastic. Secondly, the use of reflexive inverse method, the director into an arbitrary angle of liquid crystal elastomers uniaxial tensile, pure shear typical mechanical problem was solved. The results show that the liquid crystal elastomer stress, strain, temperature, degree of order, degree of biaxial, director direction, revealing the characteristics of mutual coupling. When the liquid crystal elastomer shear, or when subjected to a tensile vector direction along the non-directivity, the directivity of the liquid crystal elastomer vector rotation occurs, and induce biaxial effect. The effect of coupling due to the force of sequence, the Young's modulus of the liquid crystal elastomer foot anisotropy, pointing perpendicular to the vector direction of the Young's modulus of less than a direction parallel to, but are smaller than the Young's modulus of the neo-Hooke material. Infinitesimal deformation parallel and perpendicular to the director direction of the shear modulus of zero, showing soft features. Considered photosensitive liquid crystal molecules photoisomerization process nematic phase - isotropic phase transition on the basis of the introduction of light intensity and temperature of the liquid crystal elastomer constitutive equation was constructed light machine constitutive model. The results show that the light will change the degree of ordering of the liquid crystal elastomer, resulting light-induced contraction, and to change its elastic constant. Light through the liquid crystal elastomers, because the absorption intensity attenuation, and thus non-uniform light-induced contraction of the liquid crystal elastomer bending light so that the liquid crystal elastomer into a non-uniform gradient material. Furthermore, in the plane section assumption, we established a simple beam deflection, deflection of light bending model. The effect of the light equivalent to a light moment, so by the differential equation of the deflection curve, calculate the light-induced bending deflection curve. Were simulated under different boundary conditions for uniform illumination, bending deflection curve under the partial illumination, and thus obtain the stress distribution in the thickness direction. The results show that in our model, light and heat can jointly controlled light-induced bending of the liquid crystal elastomers. Equivalent the light bending moment over time, the light intensity, the ratio of the thickness of the beam and the light-attenuation distance, to show non-monotonic change. Light-induced bending stress show a non-uniform distribution, when no surface film, there are two or three zero-stress face. When the boundary constraints liquid crystal elastomers, resulting in a surface film force, the the film force will greatly constrained bending deflection small deflection theory is no longer applicable, you must use the large deflection theory. And the location of the local light and the half-width bending will have a greater impact. Further use of the finite element method to simulate the behavior of light-induced bending. The first liquid crystal elastomer the nonlinear ray machine constitutive equation the linearization results show that stress not only the displacement gradient symmetric part, but also on its antisymmetric part of. Due to the special nature of the constitutive equation of the liquid crystal elastomer-ray machine, we use FEPG finite element software, write your own finite element weak form file, import the built-ray machine constitutive equation, the light induced bending plane simulation of stress problems. Conclusions obtained by the finite element method with simple beam model. When the thickness of the beam with optical attenuator relatively large distance, the total stress show a non-linear distribution plane section assumption is not established even in uniform illumination is also non-uniform distribution of stress along the length.
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