| In this thesis, I give a historical review of the electrorheological (ER) fluids development, together with their potential applications, followed by an introduction to the mathematical technique used in the numerical modeling of the recently discovered giant electrorheological (GER) effect in suspensions of coated nanoparticles. A description of the salient features of the GER fluids---including the nearly linear variation of the static yield stress as a function of the applied electric field, as well as the magnitude of the yield stress exceeding the upper bound predicted by the conventional mechanism---is followed by the formulation of a new mechanism based on the model of surface saturation polarization. In this new model, the molecular dipole moment of the coating material plays an important role in enhancing the static yield to more than 100 kPa. Numerical finite element simulations based on the new mechanism are shown to yield results in excellent agreement with the experiments. The last section of the thesis presents a study of ER fluids with bi-dispersed particles, in which the small particles fills the voids between the larger dielectric spheres. It is shown that an interesting structural transition can occur within certain relative volume fractions of the small vs. large particles, and their relative dielectric constants. |
