STUDIES ON THE STEADY-SHEAR BEHAVIOR OF ELECTRORHEOLOGICAL SUSPENSIONS

The structures of nonaqueous suspensions subjected to electrical fields and continuous shear are described. Based on observations that particle strands and columns formed upon application of an electric field behave as elastic solids for small shear strains but yield above a critical strain, models for the yield stress and continuous-shear response of these electrorheological (ER) suspensions are developed. Comparison of model calculations with experimental results indicates that the yield stress is dominated by the work required to overcome electrically induced interparticle forces. The continuous-shear response of these suspensions can be understood in terms of the gradual degradation of solid-like masses of particles as the shear rate is raised. A continuum model incorporating these concepts is developed, and a comparison with continuous shear data shows an excellent model of ER suspension flow can be developed by considering suspension response as a sum of the behaviors in the zero shear rate and in the high shear rate, zero field strength regions. © 1990, American Chemical Society. All rights reserved.