Electrorheological fluid characterization via a vertical oscillation rheometer

A custom designed vertical oscillation rheometer (VOR) is used for the rheo logical measurements of electrorheological (ER) fluids consisting of 15 and 20 vol.% semiconducting polyaniline particles suspended in silicone oil. T he viscoelastic material functions, including complex viscosity and complex shear modulus, are measured via geometric parameters, measured force, and applied strain of the VOR. Viscoelastic properties of the ER fluids are als o measured as a function of applied electric field strength and particle co ncentration. The VOR, equipped with a high voltage generator, can easily be constructed and used to measure ER properties. It is further found that po lyaniline suspensions behave as viscoelastic materials in an electric field . In linear viscoelastic conditions, elasticity was promoted with the incre ment of electric field due to particle chain structure in the presence of t he applied electric field. It is also found that the applied electric field rather than particle concentration enhanced the elasticity of ER fluids. ( C) 2001 Elsevier Science Ltd. All rights reserved.