Improving the magnetorheological effect in isotropic magnetorheological rubber materials

Magnetorheological (MR) rubber materials are the solid analogue of magnetorheological fluids; i.e. their theological properties can be controlled by an applied magnetic field. However, the use of a crosslinked matrix allows larger particles to be used than in fluid matrices, and when large irregular particles are used alignment of the particles is not necessary for obtaining a substantial MR effect. We show that the absolute MR effect of isotropic MR rubber materials with large irregular iron particles is independent of the matrix material, and that the relative MR effect can be increased by the addition of plasticisers. Other ways of increasing the MR effect are to increase the magnetic field, although the materials saturate magnetically at high fields, or to use small amplitude strains. Finally, we show that the damping of isotropic MR rubbers is to some extent increased by an applied magnetic field, but that the increase is too small to be of any practical importance. (C) 2003 Elsevier Science Ltd. All rights reserved.