Magnetorheological elastomers (MREs) are a class of recently emerged smart materials whose moduli are largely influenced when exposed to an external magnetic field. The MREs are particulate composites, where micro-sized magnetic particles are dispersed inside a non-magnetic polymeric matrix. These elastomers are known for changing their mechanical and rheological properties in the presence of a magnetic field. This change in properties is widely known as the magnetorheological (MR) effect. The MR effect depends on a number of factors such as type of matrix materials, type, concentration and distribution of magnetic particles, use of additives, working modes, and magnetic field strength. The investigation of MREs’ mechanical properties in both off-field and on-field (i.e. absence and presence of a magnetic field) is crucial to deploy them in real engineering applications. The common magneto-mechanical characterization experiments of MREs include static and dynamic compression, tensile, and shear tests in both off-field and on-field. This review article aims to provide a comprehensive overview of the magneto-mechanical characterizations of MREs along with brief coverage of the MRE materials and their fabrication methods.

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A review on magneto-mechanical characterizations of magnetorheological elastomers

The dynamic modulus and the loss factor of magnetorheological elastomers (MREs) of various compositions and anisotropies are studied by dynamic torsion oscillations performed in the absence and in the presence of an external magnetic field. The emphasis is on the Payne effect, i.e. the dependence of the elastomer magnetorheological characteristics on the strain amplitude and their evolution with cyclically increasing and decreasing strain amplitudes. MREs are based on two silicone matrices differing in storage modulus (soft, G′ ∼ 103 Pa, and hard, G′ ∼ 104 Pa, matrices). For each matrix, the concentration of carbonyl iron particles with diameters of 3–5 μm was equal to 70 and 82 mass% (22 and 35 vol%, respectively) in the composite material. Samples for each filler content, isotropic and aligned-particles, are investigated. It is found that the Payne effect significantly increases in the presence of an external magnetic field and varies with the cyclical loading which reaches saturation after several cycles. The results are interpreted as the processes of formation–destruction–reformation of the internal filler structure under the simultaneously applied mechanical force and magnetic field. Impacts of matrix elasticity and magnetic interactions on the filler alignment are elucidated.

Experimental study of the magnetic field enhanced Payne effect in magnetorheological elastomers

Hysteresis of the viscoelastic properties and the normal force in magnetically and mechanically soft magnetoactive elastomers: Effects of filler composition, strain amplitude and magnetic field

Magnetodielectric effect in magnetoactive elastomers: Transient response and hysteresis

Fractional rheological models of dynamic mechanical behavior of magnetoactive elastomers in magnetic fields

A study of the influence of magnetic field on the resistivity of the magnetoactive (magnetorheological) elastomer has been conducted. The material consisted of a soft polymer matrix and magnetic fillers being powders of Fe, Ni, and the Fe–Nd–B alloy. Under the influence of the field with a value of 300 mT, the elastomer exhibited the magnetoresistive effect: The specific electric resistivity of the material was noticed to decrease by 3 orders. In addition, a significant dependency of the ability to conduct electric current was found on mechanical influence (piezoresistive effect) and combined influence of mechanical force and magnetic field. In the case considered, the behavior of the electroconductivity has a complex character.

A. V. Bakhtiiarov

Papers

Magnetoresistive Effect in Magnetoactive Elastomers