Recent Progress in Isotropic Magnetorheological Elastomers and Their Properties: A Review

Abstract

Magnetorheological elastomers (MREs) are magneto-sensitive smart materials, widely used in various applications, i.e., construction, automotive, electrics, electronics, medical, minimally invasive surgery, and robotics. Such a wide field of applications is due to their superior properties, including morphological, dynamic mechanical, magnetorheological, thermal, friction and wear, and complex torsional properties. The objective of this review is to provide a comprehensive review of the recent progress in isotropic MREs, with the main focus on their properties. We first present the background and introduction of the isotropic MREs. Then, the preparation of filler particles, fabrication methods of isotropic MREs, and key parameters of the fabrication process-including types of polymer matrices and filler particles, filler particles size and volume fraction, additives, curing time/temperature, and magnetic field strength-are discussed in a separate section. Additionally, the properties of various isotropic MREs, under specific magnetic field strength and tensile, compressive, or shear loading conditions, are reviewed in detail. The current review concludes with a summary of the properties of isotropic MREs, highlights unexplored research areas in isotropic MREs, and provides an outlook of the future opportunities of this innovative field.

Keywords: carbonyl iron particles; construction and medical applications; magneto-sensitive smart materials; magnetorheological elastomers (MRE); rheological properties.

Figure 1

Fabricated isotropic magnetorheological elastomer (MRE) sample and its dimensions [34] (reprinted with permission from Elsevier^TM).

Figure 2

Schematic of surface modification mechanism of carbonyl iron particles (CIPs) with Polyaniline (PANI) coating and fabrication of PANI-modified CIP-based isotropic MREs [91] (reprinted with permission from Elsevier^TM).

Figure 3

SEM micrographs of (a,b) pure CIPs and (d,e) PANI-modified CIPs; contact angles of a water droplet on (c) pure CIPs and (f) PANI-modified CIPs [91] (reprinted with permission from Elsevier^TM).

Figure 4

SEM micrographs of (a) CIPs-free MRE, (b) MRE with 20 wt% CIPs, (c) high-magnification micrograph of MRE, (d) histogram exhibiting CIPs size distribution in MREs, (e) XRD spectra, and (f) FTIR spectra of MREs [23] (reprinted with permission from Elsevier^TM).

Figure 5

(a) XPS spectra of MRE with 20 wt% CIPs, demonstrating carbon, oxygen, silicon, and tin elements in the selected area, presented in inset figure. (b) XPS maps and atomic percentages of elements for the selected area [23] (reprinted with permission from Elsevier^TM).

Figure 6

The 3D reconstructed images of tomography data after particle separation. (Left) Initial microstructure of particles distribution under 0-mT magnetic field and (Right) microstructure of the same sample under 250-mT magnetic field with particles chains [22] (reprinted with permission from Elsevier^TM).

Figure 7

The plot of shore A hardness as a function of magnetic particle content (phr) of EPDM-based MREs containing BIPs and CIPs [24] (reprinted with permission from Elsevier^TM).

Figure 8

Properties of the pure thermoplastic elastomers (TPEs) (dark) and TPE-based MREs (stripped) subjected to various processing cycles (R0–R3) (a) Tensile strength, (b) Elongation at break, (c) 100% Modulus, (d) 300% Modulus [30] (reprinted with permission from Elsevier^TM).

Figure 9

Dynamic properties of EPDM-based isotropic MREs, including storage modulus. (a) MRE containing CIPs; (b) MRE containing BIPs, loss modulus; (c) MRE containing CIPs; (d) MRE containing BIPs, and Tan δ; (e) MRE containing CIPs; (f) MRE containing BIPs as a function of frequency [24] (reprinted with permission from Elsevier^TM).

Figure 10

The plot of compressive force–cyclic compressive displacement under the conditions of constant peak-to-peak displacement (0.6 mm), constant frequency (0.1 Hz), various preloads, and various magnetic field strengths: (a) 0 mT, (b) 190 mT, (c) 320 mT, (d) 520 mT [89] (reprinted with permission from Elsevier^TM).

Figure 11

Stress–strain diagrams of MREs with CIPs concentration (a) 0% and (b) 30% under frequencies of 50 Hz and 200 Hz [27] (reprinted with permission from Elsevier^TM).

Figure 12

Impact of magnetic flux density on elastic shear modulus under various strain amplitudes and various excitation frequencies: (a) 2.5%, (b) 5%, (c) 10%, (d) 20% [95] (reprinted with permission from Elsevier^TM).

Figure 13

The plot of complex shear modulus vs. magnetic flux density of EPDM-based MREs with warious concentration of CIPs and BIPs (a) 5–30 phr of CIPs, (b) 2–10 phr of CIPs and 2–10 phr of BIPs [24] (reprinted with permission from Elsevier^TM).

Figure 14

The plot of storage modulus: (a) pure MREs, (b) PANI-modified MREs, and loss modulus; (c) pure MREs and (d) PANI-modified MREs vs. strain under various magnetic flux densities [91] (reprinted with permission from Elsevier^TM).

Figure 15

(a) The plot of theoretical and experimental values of initial viscosity of MREs containing different volume fractions of magnetic particles. (b) Curves of MREs’ viscosity measured during curing [45] (reprinted with permission from Elsevier^TM).

Figure 16

The magnetic force produced on IPs in (a) unconstrained and (b) constrained conditions; (c) mechanical strain on IPs under strained conditions; (d) effect of an increase in thickness on the magnetic force of particles [31] (reprinted with permission from Elsevier^TM).

Figure 17

Complex torsional stiffness values at (a) 0 A (0 T) and (b) 5 A (0.28 T) under various frequencies [31] (reprinted with permission from Elsevier^TM).

Figure 18

The Plot of the average coefficient of friction as a function of various vibration frequencies [34] (reprinted with permission from Elsevier^TM).

Figure 19

Wear depth obtained after all tests [34] (reprinted with permission from Elsevier^TM).

Figure 20

Plots of total energy density vs. cycles under different concentrations of CIPs [35] (reprinted with permission from Elsevier^TM).

Figure 21

The plot obtained from the Cole–Cole model for original TPE pellets (R*) and neat TPE matrices after each reprocessing cycle (R0–R3). The best model fits are presented by solid lines, and the materials are processed through the injection molding (IM) technique directly by R* [30] (reprinted with permission from Elsevier^TM).

Figure 22

Plot of capacitance (C) of hMRE membrane Mi-based (i = 1, 2, 3, 4) parallel plane capacitor as a function of magnetic field intensity (H) [97] (reprinted with permission from Elsevier^TM).