Giant magnetostriction in low-concentration magnetorheological elastomers

Abstract

Magnetorheological elastomers (MREs) are smart composite materials that can vary their mechanical properties under the influence of an external magnetic field. In the present work, we report the giant magnetostriction of low-concentration isotropic and anisotropic MREs, by combining a soft elastomer matrix with helicoidal-shaped particles. Magnetic characterization has shown high magnetic sensitivity of the anisotropic MREs near H ≅ 0, which can be up to 400% larger comparing to the isotropic counterparts. The determination of tensile elastic modulus (E) of the MREs indicates that the anisotropic samples become softer when the magnetic field is increased from H = 0 to H = 200 Oe. Due to the higher field sensitivity of the anisotropic composites, the magneto-induced elongation contributes to the increase in the overall strain when measuring the elastic modulus at low deformation. This compliance of the MRE explains the decrease in E from H = 0 to H = 200 Oe. Magnetostriction measurements were performed and giant strain values up to 3731 ppm were obtained for isotropic samples with 3.4 vol% of Hiperco particles under a field of H = 3500 Oe. This result stands out from the literature due to the giant induced elongation, with reduced volume fraction of particles. The developments of this work are a step forward on improving smart and efficient composites, that can have many applications, such as switches, controllable valves, and vibration attenuators.