Critical bending and shape memory effect in magnetoactive elastomers

Abstract

The results of a study of magnetoactive elastomers (MAEs) consisting of an elastomer matrix with embedded ferromagnetic particles are presented. A continuous critical bending induced by the magnetic field, characterized by a critical exponent for the bending magnitude, and the derivative of which has a singularity in the critical region is reported for the first time. The mechanical stability loss and the symmetry reduction of the magnetic state, which are interrelated with each other, take place at the critical point. The magnetization in the high-symmetric state (below the critical point) is directed along the magnetic field and the torque is absent. Above the critical point, the magnetization and the magnetic field are noncollinear and there arises a torque, which is self-consistent with the bending. The magnetic field dependence of the MAE bending was found to have a hysteresis, which is associated with the magneto-rheological effect. The shape memory effect was also obtained for the MAE bending in a cycle consisting of magnetization, cooling (at H ≠ 0), and heating (at H = 0). The influence of the critical glass transition temperature of the matrix, as well as its melting/solidification temperature, on the magnetic shape memory effect was studied.

Magnetoelectric Response of Laminated Cantilevers Comprising a Magnetoactive Elastomer and a Piezoelectric Polymer, in Pulsed Uniform Magnetic Fields

“…As explained in Ref. [ 26 ], the magnetization of a soft-magnetic beam upon its bending in a magnetic field, which is nominally perpendicular to the initial beam plane, is not co-directional with the magnetic field. If the magnetization is not collinear with the magnetic field, then a torque from the magnetic field acts on that beam.…”

“…In [ 26 ], a beam from an MAE filled with nickel particles was used; the direction of the beam’s deflection changed with the change in the polarity of the applied magnetic field. This was explained by the presence of residual magnetization.…”

“…In our control experiment, we clamped an MAE-PEP cantilever horizontally (α = 0°) and the polarity of the applied magnetic field was changed in a square-wave fashion, see Figure 10 . It is seen that the deflection direction did not change, i.e., the MAE material seemed to behave as the particles would be ideally soft magnetic [ 26 ]. This result agreed with the measurements of magnetic properties.…”

“…The bending mechanism of the composite MAE–PEP cantilever is described in Ref. [ 26 ]. If a soft-magnetic planar MAE cantilever would be directed perpendicular to the uniform magnetic field, it would not be bent.…”

Flowability of Gel-Matrix and Magnetorheological Response for Carrageenan Magnetic Hydrogels

“…Magnetic soft material consisting of polymeric matrix and magnetic particles demonstrates drastic changes in physical properties in response to magnetic fields, and it has great potential in various applications [1][2][3]. To achieve a high and fast response of the elasticity change, a variety of improvements have been reported [4][5][6][7][8][9].…”