Importance of interparticle gaps for tailoring the properties of composites

Abstract

Electroactive elastomers are composites made of solid particles embedded in an elastomeric network whose electrical, mechanical or optical properties can be changed by the application of an electric or a magnetic field. These materials have obviously a strong connection with ER and MR fluids and can be more appropriated for some applications. We present results concerning the conductivity, magnetic permeability and elasticity of an elastomer filled with iron or carbonyl iron particles. We show that the change of elastic properties obtained by the application of a magnetic field depends strongly on the gap between the particles. We explain quantitatively the experimental results with the help of finite element calculation to predict the magnetic forces between the particles. The effect of a magnetic field on the electrical resistance is also investigated and we show that we can obtain a huge decrease of the resistance by the application of a magnetic field.