Piezoresistivity of magnetorheological elastomers.

Magnetorheological elastomers are smart materials made by aligning magnetic microparticles inside a liquid polymer before the curing process has started. Once cured, the composite presents new properties such as a large change of elasticity when applying a magnetic field. We analyze here another specific property of these materials which is the piezoresistivity. Two cases are studied: one where the particles inside the matrix are not in contact and the other where they are in contact. We show that in the first case we observe an exponential dependence of the resistivity versus pressure and in the second case a power law dependence. These behaviors are explained with the help of a conductivity model based on the dependence of the tunnel effect on the area of contact.