Research On Nonlinear Deformation And Buckling Morphology Of Glassy Nematic Liquid Crystal Sheets

Under external stimulation, glassy nematic sheets generate spontaneous deformations with reversible contraction along and expansion perpendicular to the director. According to the different in-plane alignment of the director, nematic sheets produce different three-dimensional buckling morphologies. Due to this mechanical response, nematic sheets have wide application prospects for devices with adjustable shapes. In order to have some insight into the deformation of nematic sheets, we do research on the deformation of glassy nematic liquid crystal sheets with arbitrary in-plane director fields.We first formulate a theoretical model, which is based on the Foppl-von Karman plate theory, to describe the deformation of nematic sheets containing in-plane director fields. In this model, spontaneous deformations are treated as eigenstrains. The elastic anisotropy and geometric nonlinearity are taken into account. Governing equations are obtained by the principle of virtual work.Then we develop a kinetics approach to numerically solve the governing equations. A hypothetical sheet is introduced to simplify the solving process of equilibrium equations. Nematic sheets are treated as overdamped evolution systems driven by energy release, so that their equilibrated morphologies can be obtained directly from the steady-state solutions.Through specific examples, we verify the influence of the elastic anisotropy on the solution of equilibrated morphology, and discuss the impact of the geometric size and eigenstrain value on the deformed shapes. Furthermore, the effects of geometric shapes and eigenstrain fields on the deformation in nematic sheets are discussed.The work in this dissertation provides a simple and effective approach for solving the deformation of glassy nematic sheets with in-plane director fields. It is also proved that the elastic anisotropy of nematic materials should not be neglected in solving the deformed shape of nematic sheets. The discussion about the influence of geometric shapes and eigenstrain fields on the deformation provides an insight into the design of three-dimensional shapes in nematic sheets.