Investigating new symmetry classes in magnetorheological elastomers: cantilever bending behavior

Abstract

This work defines and examines four classes of magnetorheological elastomers (MREs) based upon permutations of particle alignment-magnetization pairs. Particle alignments may either be unaligned (e.g. random) or aligned. Particle magnetizations may either be soft-magnetic or hard-magnetic. Together, these designations yield four material types: A-S, U-S, A-H, and U-H. Traditional MREs comprise only the A-S and U-S classes. Samples made from 325-mesh iron and 40 μm barium hexaferrite powders cured with or without the presence of a magnetic field served as proxies for the four classes. Cantilever bending actuating tests measuring the magnetically-induced restoring force at the cantilever tip on 50 mm × 20 mm × 5 mm samples yielded ∼350 mN at μ 0 H = 0.09 T for classes A-H, A-S, and U-S while class U-H showed only ∼40 mN. Furthermore, while classes U-S and A-S exerted forces proportional to tip deflection, they exerted no force in the undeformed state whereas class A-H exerted a relatively constant tip force over its entire range of deformation. Beam theory calculations and models with elastic strain energy density coupled with demagnetizing effects in the magnetic energy density were used to ascertain the magnitude of the internal bending moment in the cantilever and to predict material response with good results. This work highlights the ability of the newly developed A-H MRE materials, and only that material class, to operate as remotely powered bidirectional actuators.

Mechanics of magneto-active polymers

“…A large number of experiments have been carried out to study the effect of matrix and filler composition (e.g. Bellan and Bossis, 2002;Nikitin et al, 2006;Lockette et al, 2011), relative alignments of particles, mechanical, magnetic inputs (e.g. Varga et al, 2006;Filipcsei et al 2007;Rao et al, 2010;), frequency of mechanical and magnetic loads (e.g.…”

Rate dependent finite deformation of magneto-active polymers

“…The first process dominates in soft-magnetic particles, such as carbonyl iron particles, 12,14 which are often used in MAPs. The second process, which takes place in hard-magnetic particles, such as barium hexaferrite powder, 18 dissipates energy and the rate of the process may be dependent on the viscoelastic matrix. In the current paper, we only consider the soft-magnetic materials, and assume that the magnetic domain switch reaches equilibrium much faster than the relaxation of matrix.…”

“…14,16 In addition to the orientations, the magnetizations, volume fraction and size of particles also have significant effect to the properties of MAPs. [17][18][19] Recently, four classes of MAPs have been developed based on different permutation of particle alignments and magnetizations. 18 The current paper will focus on the magnetic-field-induced finite deformation of isotropic MAPs.…”

“…[17][18][19] Recently, four classes of MAPs have been developed based on different permutation of particle alignments and magnetizations. 18 The current paper will focus on the magnetic-field-induced finite deformation of isotropic MAPs.…”

“…Linear viscoelastic models such as Maxwell and Kelvin-Voigt models have been used to capture the dynamic responses of MAPs in cyclic magnetic fields. 12,18,34 However, these simple rheological models are limited to small deformations in one dimension. The motivation of this paper is to provide a three dimensional model which can fully couple the magnetic field and large viscoelastic deformation in MAPs.…”