INVESTIGATION INTO THE USE OF LIQUID-CRYSTALLINE MATERIALS IN ELECTRORHEOLOGICAL FLUIDS

The ER activity of a number of ER fluids incorporating liquid crystall ine (LC) and non-LC materials have been measured using a laminar-flow shear cell. The results from this static study are presented and clear ly show that the unique self-organising and anisotropic physical prope rties of the LC materials contribute greatly to the ER activity of LC based ER fluids. A more in-depth evaluation was then carried out on a LC based ER fluid which involved measurements of the steady state beha viour, under various operational conditions, and the results compared with those from two conventional silicone based fluids. From this dyna mic study it was found that within the shear rates tested, for an elec tric field strength above 1 kV mm(-1) there existed a linear relations hip. culminating in a shear stress of 12 kPa at an electric field stre ngth of 4 kV mm(-1). The unique property of the shear stress increasin g with increase in the shear rate makes LC based ER fluids an exciting area for further research and this could be of considerable importanc e in their use in a variety of control systems.