Mechanical properties of magnetorheological elastomers under shear deformation

In this paper, urethane magnetorheological elastomers (MREs) consisting of carbonyl-iron particles in a polyurethane matrix were studied. The volume fraction of particles was equal to 11.5%. Three types of ferromagnetic particles were used, with average particle size ranging from 1 to 70 μm. The elastic (storage) modulus G′ was measured as a function of angular frequency ω and strength of magnetic field. The measured G′ values were approximated with empirical model. The highest magnetorheological effect has been found for samples with 6–9 μm carbonyl-iron powder. The highest increase in the yield stress is observed for samples with particles aligned at 30° to the magnetic field lines. It has been found that rheological properties strongly depend on the MRE microstructure, in particular on the size/shape of particles and their arrangement. By optimizing the particles size, shape and alignment, the stiffness of MREs has been increased under applied magnetic field.