Experimental and theoretical investigations on magnetoelastic shear behavior of isotropic MR elastomers under gradient magnetic fields

The magnetoelastic lap-shear behaviors of isotropic magnetorheological (MR) elastomers containing different concentration of silicon oil were investigated under a gradient magnetic field produced by a permanent magnet. Taking into account the elastic property of matrix material and the interaction between the magnetized particles and external magnetic field, an extended theoretical model to qualitatively elucidate the magnetoelastic shear responds of this kind of magnetoactive composites was proposed. Results show that the shear modulus of the isotropic MR elastomer is markedly enhanced with increasing magnetic field, but declined with an increase of the concentration of silicon oil in compound sample. The magnetoelastic performances, such as magnetic-field induced modulus, magnetorheological effect, etc., are strongly dependent on the axial magnetic field gradient. The lower gradient of the applied magnetic field leads to more significant reinforcing effect than the higher one, mainly because there is more magnetic energy input per unit volume. It can be concluded form the comparison between theoretical modeling and experimental results that the model can well describe the magnetoelastic properties of MR elastomers in different conditions. The effect of particle volume fractions, matrix's elasticity coefficient and gradient of magnetic field on magnetorheological effect of MR elastomers is presented as well. The results might be able to provide some basic guidelines for design and optimization of practical application of related projects.