Development of an Electrically Controllable Damper Using a Liquid Crystal

Abstract

This paper describes a new electrically controllable damper that uses a liquid crystal (LC) as the working fluid. LC is a homogeneous organic liquid characterized by the long-range order of its molecular orientation. The sample LC used in this work is a thermotropic, low molecular-weight LC which appears in the nematic phase, and was originally developed for display devices. The molecular orientation of the nematic phase is characterized by slender ellipsoidal shape molecules, the main axis of which can be controlled by applying an electric or magnetic field. When an electric field is applied to a LC, the orientation order of the molecules becomes parallel to the applied electric field, causing the apparent viscosity to increase. This phenomenon is known as the electroviscous effect. To study the application of the electroviscous effect of a LC to a controllable mechanical damping device, a prototype controllable damper was constructed and its performance was examined. In this damper, a piston, equipped with several concentric cylindrical electrodes attached to the piston rod, moves in the liquid crystal. During the reciprocal movement of the electrodes, LC flow through the electrodes is controlled by applying electric voltage to the latter. Damper performance was investigated under various DC electric field strengths, piston oscillation amplitudes and frequencies. The results show that the controllable damping force was three times larger with the application of an electric field than that without, and that the range of force variation was kept at the same level regardless of the frequency and amplitude of piston motion.