Electrorheology of whisker suspensions

The rheological properties of suspensions of aluminum berate in a silicone oil were measured in electric fields. On the application of electric fields , the suspensions are converted from viscous fluids to plastic bodies with high yield stresses. The particles all align into chains spanning the elect rode gap in electric fields. The plastic responses are attributed to the de formation of chains. For sphere suspensions, the yield stress increases exp onentially with particle concentration. The systems consist of a collection of thick columns constructed by the aggregates of many chains. Since the s trength of an individual column rapidly increases with column thickness, th e yield stress shows non-linear dependence on the particle concentration. F or whiskers suspensions, the yield stress linearly increases with particle concentration. Although the whiskers are easily oriented and fibrous struct ures are developed between electrodes, the aggregates of whiskers comprise highly branched chains. The linear relation for whisker suspensions indicat es that the yield stress is proportional to the total number of chains. The yield process of electrified suspensions is strongly affected by the geome try of primary particles. (C) 1999 Elsevier Science B.V. All rights reserve d.