Abstract
Elongations of magnetoactive elastomers (MAEs) under ascending–descending uniform magnetic fields were studied experimentally using a laboratory apparatus specifically designed to measure large extensional strains (up to 20%) in compliant MAEs. In the literature, such a phenomenon is usually denoted as giant magnetostriction. The synthesized cylindrical MAE samples were based on polydimethylsiloxane matrices filled with micrometer-sized particles of carbonyl iron. The impact of both the macroscopic shape factor of the samples and their magneto-mechanical characteristics were evaluated. For this purpose, the aspect ratio of the MAE cylindrical samples, the concentration of magnetic particles in MAEs and the effective shear modulus were systematically varied. It was shown that the magnetically induced elongation of MAE cylinders in the maximum magnetic field of about 400 kA/m, applied along the cylinder axis, grew with the increasing aspect ratio. The effect of the sample composition is discussed in terms of magnetic filler rearrangements in magnetic fields and the observed experimental tendencies are rationalized by simple theoretical estimates. The obtained results can be used for the design of new smart materials with magnetic-field-controlled deformation properties, e.g., for soft robotics.
Highlights
Magnetoactive elastomers (MAEs) are promising materials for manufacturing magnetic-field controlled linear actuators [1,2,3,4,5], in particular for soft robotics [6]
The purpose of this paper is twofold: First, we present a simple experimental setup allowing one to measure the strain of magnetoactive elastomers (MAEs) samples with the shear modulus as low as 30 kPa
Three of them were manufactured with the same iron content wFe of 80 mass% (φ ≈ 33 vol%) and each having effective shear storage moduli in the absence of a magnetic field G0
Summary
Magnetoactive elastomers (MAEs) are promising materials for manufacturing magnetic-field controlled linear actuators [1,2,3,4,5], in particular for soft robotics [6]. The physical origin is not the magnetization–strain coupling caused by the quantum spin–orbit interaction in ferromagnetic inclusions but the restructuring (RS) of the filler, i.e., changes in mutual arrangement of magnetized micrometer-sized inclusions, caused by magnetic interactions and restricted by the matrix elasticity. Such a significant reconfiguration becomes possible when the matrix is sufficiently compliant (Young’s modulus < 100 kPa). Other magnetoelastic effects related to MS, the Villary effect [22,23] and the Wiedemann effect [24], have been reported in compliant (mechanically soft) MAE materials as well
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