Anisotropic Magnetorheological Elastomers Research Articles

The Damping Properties of Plate-Like Magnetorheological Elastomer

This paper aims to investigate the damping properties of plate-like carbonyl iron particle (CIP) magnetorheological elastomer (MRE). The damping properties of MRE is mainly dependent on the strength of magnetic field. Anisotropic MRE was fabricated under various magnetic fields strength (70, 210, 345, and 482 mT) and its damping property prior to frequency-dependent was measured using a rheometer. Firstly, the plate-like CIP was first synthesized from spherical CIP using a ball-milling method. The microstructure of plate-like CIP was observed using low vacuum scanning electron microscope. Subsequently, two types of MREs which are isotropic and anisotropic were fabricated using 70 weight percent (wt.%) of plate-like CIP. The experimental results showed that the anisotropic MRE has lower damping factor than isotropic MRE. Meanwhile, the damping factor increases with the increase of frequency.

Simulation and Validation of an Anisotropic Magnetorheological Elastomers Mold with Various Alignment Angles

In this study, anisotropic magnetorheological elastomers (MREs) mold design with capability of aligning the filler in several angles (0 ̊, 45 ̊, and 90 ̊) were developed. The mold was equipped with electromagnet coil to generate the magnetic flux. The distribution of magnetic flux density in the mold and inside the chamber was investigated by using finite element magnetic analysis. Magnetic flux density of 0.3 T was considered best value to form good particle alignment in the matrix. Moreover, the mold design was fabricated using same material as in the simulation. The magnetic flux density was taken at casing wall and measured by gauss-meter. The data was compared with simulation results. The differences between experimental and simulation is in the range of 6-40 mT. Since the difference is insignificant, it can be said that the data is valid. Finally, the model can be used for further magnetic flux density prediction inside the chamber. In the simulation, it was found that the current needed to generate at least 0.3 T inside the chamber for 0 ̊, 45 ̊, and 90 ̊ are 0.2A, 0.1A, and 3A, respectively.

Microstructure and dynamic mechanical properties of magnetorheological elastomer based on ethylene/acrylic elastomer prepared using different manufacturing methods

Magneto-rheological elastomer (MRE) is a kind of smart material based on elastomer matrix and it is divided into isotropic (i-MRE) and anisotropic MRE (a-MRE) depending on the magnetic particle arrangement. In the i-MRE, carbonyl iron particles (CIP) are randomly dispersed, while they form a chain-like structure in the a-MRE. Two manufacturing procedures of a-MRE have been introduced. The a-MRE-1 was manufactured by one-step process involving application of magnetic field and curing of matrix simultaneously. On the other hand, a-MRE-2 was manufactured by two-step process in which the magnetic field was applied to induce CIP orientation and then the matrix was cured. The microstructure and mechanical properties of MRE were characterised by scanning electron microscope, universal testing machine and dynamic mechanical analysis. The results showed that the CIP content in MRE had no effect on the cure properties. A chain-like structure existed in a-MRE-1, whereas the orientation structure of CIP in the a-MRE-2 was not as clear as that in a-MRE-1. The tensile strength of a-MRE-1 was the lowest because no interfacial reaction occurred between the CIP and the rubber molecules chain, whereas i-MRE had the highest tensile strength.

Magnetic circuit analysis to obtain the magnetic permeability of magnetorheological elastomers

The magnetic permeability of magnetorheological elastomers must be known for their long-term use in the actual engineering systems. In this article, the magnetic permeability of both isotropic and anisotropic magnetorheological elastomers has been determined using a new method. The magnetic induction was measured and a closed magnetic circuit analysis was carried out to obtain the magnetic permeability of magnetorheological elastomers for both isotropic and anisotropic magnetorheological elastomers with 10%–50% volume concentration of carbonyl iron particles. The magnetic permeability was increased with increasing particle concentration for both isotropic and anisotropic magnetorheological elastomers as we could expect. The isotropic permeability is always lower than the anisotropic permeability. The maximum relative permeability value of 6.6 was obtained for 50% particle volume concentration. The experimental results also show a good agreement with theoretical predictions and previous investigations.

Study on a new self-sensing magnetorheological elastomer bearing

The complexity of a semi-active vibration isolation system results in the difficulty of realizing its role on impact load effectively. Thus, a new self-sensing bearing based on modified anisotropic magnetorheological elastomer (MRE) is proposed in this study. This self-sensing bearing was fabricated by dispersed multi-walled carbon nanotubes and carbonyl iron particles into polydimethylsiloxane matrix under a magnetic field. The working conditions of the bearing were analyzed and decoupled. An optimal structure size of the bearing was selected and used for setting up the experiment test system. The self-sensing characteristic of the MRE bearing under the multi-field coupling of load and magnetic fields was then investigated by this test system. Results showed that the resistance of the modified MRE, in which a preload was applied by the bearing, could change approximately 28%–56% under extrusion force, mechanical force, and external magnetic field. The vibration isolation performance was tested based on the self-sensing characteristic. The bearing had excellent mechanical properties, which could reduce at least 30% of vibration. Thus, the modified MRE of the magnetorheological elastomer bearing could be simultaneously used as an actuator and a sensor.

Investigations on the properties of NH4HCO3 filled natural rubber based magnetorheological elastomers (MREs)

Various anisotropic magnetorheological elastomers (MREs) were synthesized using the rubber mixing technique. Magnetic and temperature distributions of the experimental equipment and test instruments were analyzed by the ANSYS. NH4HCO3 was filled in the natural rubber matrix to modify properties of MREs. Microstructures and compositions of samples were studied by the scanning electron microscope (SEM), the energy dispersive x-ray spectroscopy (EDAX) analysis and x-ray powder diffraction (XRD). Via vibrating sample magnetometer (VSM) and density functional theory (DFT) method, the magnetic property of carbonyl iron (CI) was illuminated. The shear storage modulus and MR effect of MREs were investigated by the dynamic mechanical analyzer (DMA). It indicated that distributions of magnetic and temperature in the experimental and testing devices were uniform. Before vulcanization, CI particles were uniformly distributed in the matrix, while a CI chain structure was formed and embedded in the matrix after the vulcanization process. Moderate addition of NH4HCO3 accelerated the rubber vulcanization and enhanced the MR effect.

Design of magnetic Circuit Simulation for Curing Device of Anisotropic MRE

The strength of magnetic field during fabrication of magnetorheological elastomer (MRE) plays a crucial role in order to form a pre-structured MRE. So far, gaussmeter were used to determine the magnetic intensity subjected to the MRE during curing. However, the magnetic flux reading through that measurement considered less accurate. Therefore, a simulation should be done to figure out the magnetic flux concentration around the sample. This paper investigates the simulation of magnetic field distribution in a curing device used during curing stage of anisotropic magnetorheological elastomer (MRE). The target in designing the magnetic circuit is to ensure a sufficient and uniform magnetic field to all the MRE surfaces during the curing process. The magnetic circuit design for the curing device was performed using Finite Element Method Magnetic (FEMM) to examine the magnetic flux density distribution in the device. The material selection was first done instantaneously during a magnetic simulation process. Then, the experimental validation of simulation was performed by measuring and comparing the actual flux generated within the specimen type and the one from the FEMM simulation. İt apparent that the data from FEMM simulation shows an agreement with the actual measurement. Furthermore, the FEMM results showed that the magnetic design is able to provide sufficient and uniform magnetic field all over the surfaces of the MRE.

Two Way Stiffness Tuning Of Magnetorheological Elastomer- Shape Memory Alloy Composite

Structural vibration control by tuning structural material modulus through external stimuli is great deal of interest for researchers. Shape memory alloy (SMA) is kind of smart material whose modulus can be varied by changing its temperature. Temperature dependent change in modulus of SMA during phase transformation is stiff and nonlinear which inducts difficulties for getting smooth structural stiffness change to alter its dynamic behavior. This paper deals with the work wherein, SMA is combined with magnetorheological elastomer (MRE) to form composite. MRE is another smart material whose shear modulus consequently stiffness can be changed by exposing it to variable magnetic field. Smart MRE-SMA composite has been studied analytically for stiffness variation by combining Maxwell form of three parameter constitutive viscoelastic material model, model for magnetic field dependent change in shear modulus for anisotropic MRE and temperature dependent modulus of SMA. The composite is fabricated, tested for stiffness change with respect to external stimuli by natural frequency measurement method and the results are compared with analytical study. The result show that the stiffness nonlinearity exists in SMA during transformation phase has been minimized by wisely selecting values of temperature and strength of magnetic field simultaneously. Significant level of smooth stiffness change is achieved by proper tuning of SMA temperature and strength of magnetic field.

Design and experimental research of a magnetorheological elastomer isolator working in squeeze/elongation–shear mode

Due to the properties of controllable stiffness and damping, a novel isolator based on magnetorheological elastomers is introduced in this article. According to the experimental results, the initial vertical stiffness and damping coefficient of the magnetorheological elastomer isolator are 1.14 × 106 N/m and 495.8 N s/m, respectively. The relative increase in stiffness and damping is 66.57% and 45.55%, respectively. The isolation transmissibility and root mean square of acceleration response are reduced by 41.2% and 65.3%, respectively. To describe the magnetic-induced stress–strain relationship of the anisotropic magnetorheological elastomers, a theoretical model is presented as magnetorheological elastomers working in squeeze/elongation and shear modes simultaneously. Then, the stiffness formula relating to the magnetic field, strain, and the other demanding parameters is deduced. The analytical results of the stiffness formula are fairly in agreement with the experimental data.

Energy conversion in magneto-rheological elastomers

Magneto-rheological (MR) elastomers contain micro-/nano-sized ferromagnetic particles dispersed in a soft elastomer matrix, and their rheological properties (storage and loss moduli) exhibit a significant dependence on the application of a magnetic field (namely MR effect). Conversely, it is reported in this work that this multiphysics coupling is associated with an inverse effect (i.e. the dependence of the magnetic properties on mechanical strain), denoted as the pseudo-Villari effect. MR elastomers based on soft and hard silicone rubber matrices and carbonyl iron particles were fabricated and characterized. The pseudo-Villari effect was experimentally quantified: a shear strain of 50 % induces magnetic induction field variations up to 10 mT on anisotropic MR elastomer samples, when placed in a 0.2 T applied field, which might theoretically lead to potential energy conversion density in the mJ cm-3 order of magnitude. In case of anisotropic MR elastomers, the absolute variation of stiffness as a function of applied magnetic field is rather independent of matrix properties. Similarly, the pseudo-Villari effect is found to be independent to the stiffness, thus broadening the adaptability of the materials to sensing and energy harvesting target applications. The potential of the pseudo-Villari effect for energy harvesting applications is finally briefly discussed.

Dynamic mechanical properties of isotropic/anisotropic silicon magnetorheological elastomer composites

This study examines the principle of combining isotropic and anisotropic magnetorheological elastomers (MRE) in parallel and series configurations, to adjust the zero-field dynamic stiffness and damping capability of silicon MREs without compromising MR effect. The dynamic mechanical properties can be further tailored by adjusting the isotropic/anisotropic ratio. Damping of parallel configuration isotropic/anisotropic composites can be increased by combining MREs made with iron particles of small (4–6 μm) and large (<220 μm) diameter. In addition, we tested a novel anisotropic elastomer that combines two anisotropic MREs, with their particles aligned in different directions to achieve similar dynamic stiffness, damping and magnetorheological effect in those directions. The magnetorheological effect of the novel anisotropic/anisotropic composite MRE is 10% higher than that of pure anisotropic MRE. The axial, longitudinal and transverse dynamic mechanical properties, magnetorheological effect and the magnetic field-strain amplitude coupling effects were examined under a dynamic compressive strain where the amplitude was varied from 0.25% to 1.5%.

Linear magneto-viscoelastic model based on magnetic permeability components for anisotropic magnetorheological elastomers

A new magneto-viscoelastic model is presented for anisotropic magnetorheological elastomers (MREs), which combines the dynamic behaviour and magnetic permeability components. Five samples were synthesised with different particle contents. Dynamic properties were measured using a rheometer equipped with a magnetorheological cell. A four-parameter fractional derivative model was used to describe MRE viscoelasticity in the absence of a magnetic field. The magnetic permeability of each sample was measured with a vibrating sample magnetometer. From experimental measurements of longitudinal and transverse components of the magnetic permeability, the dependency with magnetic field was modelled. The new magneto-induced modulus model proposed in this work is based on the model developed by López-López et al. [19] for magnetorheological fluids, and was adapted for anisotropic MREs. The proposed model includes the longitudinal and transverse components of magnetic permeability, and it is valid for the linear viscoelastic region of anisotropic MREs. The errors between experimental values and the values predicted by the model do not exceed 10%. Hence, a new linear magneto-viscoelastic model for anisotropic MREs is developed, which predicts the effect of magnetic field on the dynamic shear modulus as a function of magnetic field intensity and frequency.

Anisotropic magnetorheological elastomers for mechanical to electrical energy conversion

MagnetoRheological Elastomers (MREs) have been widely used for actuation purposes in numerous applications (e.g., vibration damping), thanks to their magnetic-field controllable shear modulus. Nevertheless, the converse effect, namely, the modification of the magnetic properties through the application of a shear strain or stress has been barely studied. Hence, the purpose of this paper is to investigate such a possibility, both qualitatively and quantitatively, through the modeling of the rotation of particle segments induced both by the mechanical and magnetic solicitations in the case of anisotropic MREs. Such a demonstration, along with experimental validations, therefore allows envisaging new application fields for such materials.

Enhancement of radio-absorbing properties and thermal conductivity of polysiloxane-based magnetorheological elastomers by the alignment of filler particles

A design for the fabrication of more effective, thin, light-weight radio-absorbers (RAs) based on magnetorheological elastomers (MREs) is demonstrated. Carbonyl iron (CI) particles were incorporated into polydimethylsiloxane matrix either homogeneously (isotropic) or with preferential orientation into chain-like structures (anisotropic). The reflection coefficient (R) of MRE-based single-layer metal-backed RAs was calculated on the basis of transmission line theory. The results show that the orientation of CI particles strongly enhances the permittivity of the systems, while preserving their permeability, which ultimately manifests itself in enhanced absorption of electromagnetic (EM) energy and reduced thickness of RAs. Thus, RAs based on anisotropic MREs are characterized by superior EM shielding capability in the microwave frequency range compared to their isotropic analogues, which offers great practical as well as economic advantages. Moreover, the thermal conductivity of both types of RAs was investigated, since efficient energy dissipation is important to prevent heat build-up under a radio-absorbing shield and thus to extend the service life of the protected device.

Tunable friction performance of magneto-rheological elastomer induced by external magnetic field

In order to investigate the magnetic-induced friction properties of magneto-rheological elastomers, isotropic and anisotropic magneto-rheological elastomers are fabricated, tribological testing setup is built, and the friction experiment is carried out. The experimental results show that the isotropic magneto-rheological elastomer has a decreasing friction coefficient with magnetic field applied, which is also affected by particle volume fraction. The influence of magnetic field on friction coefficient of the anisotropic magneto-rheological elastomers is not monotonic. The experimental results also show that the friction coefficient of magneto-rheological elastomers decreases with the increase in load for both isotropic and anisotropic magneto-rheological elastomers in most circumstances. The volume fraction of carbonyl iron powders being around 10% is the best for magneto-rheological elastomers in tuning friction. The tunable range of friction could be as high as 25% under a magnetic field of 0.25 T. Images of the magneto-rheological elastomer interfaces show that the surface roughness is reduced by about 20.7% when a magnetic field of 0.5 T is applied. The aggregation phenomenon is observed on the surface of the magneto-rheological elastomer under a magnetic field. On the basis of three-dimensional surface topography, a preliminary model for the aggregation of micro asperities on the surface of the magneto-rheological elastomer is built to interpret the influence of the magnetic field on the tribological properties of magneto-rheological elastomers.

Fabrication and characterisation of anisotropic magnetorheological elastomer with 45° iron particle alignment at various silicone oil concentrations

In this study, anisotropic magnetorheological elastomers with 0% and 15% weight fractions of silicone oil were fabricated under a magnetic field that was rotated with a 45° angle so that the iron particle alignment inside the magnetorheological elastomer was 45° to the direction of flat magnetorheological elastomer. Scanning electron microscopic images confirmed the aligned structure of iron particles and showed that the sample with 15% silicone oil contribution resulted in a less volume fraction of iron particles. The magnetorheological elastomers were then tested in an oscillatory pure shear mode at different shear strain amplitudes under different magnetic flux densities to measure their dynamic viscoelastic properties. The testing results showed that the magnetorheological elastomer with 15% silicone oil had lower zero-field storage and loss moduli and also had higher maximum magnetorheological effect than the magnetorheological elastomer with 0% silicone oil. Because of the 45° iron particle alignment, the storage modulus of the magnetorheological elastomers had a higher value in a particular direction than its contrary direction. These unique properties made the magnetorheological elastomers with 45° iron particle alignment to be potentially used in industry where extra support is needed in a particular direction.

Formation of core–shell structured complex microparticles during fabrication of magnetorheological elastomers and their magnetorheological behavior

To improve mechanical and magnetorheological properties of magnetorheological elastomers (MREs), a facile method was used to fabricate high-performance MREs which consisted of the core–shell complex microparticles with an organic-inorganic network structure dispersed in an ethylene propylene diene rubber. In this work, the proposed magnetic complex microparticles were in situ formed during MREs fabrication as a result of strong interaction between matrix and CIPs using carbon black as a connecting point. The morphology of both isotropic (i-MREs) and anisotropic MREs (a-MREs) was observed by scanning electron microscope (SEM). The effects of carbonyl iron particle (CIP) volume content on mechanical properties and hysteresis loss of MREs were investigated. The effects of CIP volume content on the shear storage modulus, MR effect and loss tangent were studied using a modified dynamic mechanical analyzer under applied magnetic field strengths. The results showed that the orientation effect became more pronounced with increasing CIPs in the a-MREs, whereas CIPs distributed uniformly in the i-MREs. The tensile strength, tear strength and elongation at break decreased with increasing CIP content up to 40 vol.%, while the hardness increased. It is worth noting that the tensile strength of i-MREs and a-MREs containing 40 vol.% CIPs still had high mechanical properties as a result of good compatibility between complex microparticles and rubber matrix. The MR performance of shear storage modulus and damping properties of MREs increased remarkably with CIP content due to strong dipole–dipole interaction of complex microparticles. Besides, the hysteresis loss increased with increasing CIP content as a result of magnetic field induced interfacial sliding between complex microparticles.

The conductive three dimensional topological structure enhanced magnetorheological elastomer towards a strain sensor

Conductive magnetorheological elastomers (MREs) consisting of carbonyl iron particles (CIPs), polydimethylsiloxane matrix and carbon nanotube (CNT) covered polyurethane sponge (PUS) were developed. The CIPs were linearly orientated within the porous PUS and the magnetic saturation modulus of PUS-reinforced anisotropic MRE was 1.3 MPa when CIPs content was 70 wt%. This MRE presented typical magnetorheological (MR) effects and the shear storage modulus increased from 0.49 MPa to 0.64 MPa after reinforcing the anisotropic MRE with PUS. Owing to the presence of the CNTs on the PUS networks, the final MRE was conductive. The electrical resistance of the MRE increased with increasing tensile strain, ranging from 27.5 kΩ to 30.5 kΩ at various tensile rates (50, 100, 150, 200, 250 and 300 mm/min respectively). As a result, the smart MRE was effective in a flexible, sensitive and reversible strain sensor.

Magnetorheological elastomer based on silicone rubber, carbonyl iron and Rochelle salt: Effects of alternating electric and static magnetic fields intensities

A mixture consisting of silicone rubber, carbonyl iron, Rochelle salt powder and catalyst is pressed between two plane electrodes until it reaches a thickness of 0.62mm. The polymerization of the mixture is performed in a transverse magnetic field, and a membrane based on an anisotropic magnetorheological elastomer is obtained. We study the influence of the effective intensity of an alternating electric field superimposed in the direction of static magnetic field intensity, on the relative electrical resistance, deformation and tension fields, and respectively on the elastic constant of the membrane. We present and discuss the obtained results.

The effect of silane coupling agent on the dynamic mechanical properties of iron sand/ natural rubber magnetorheological elastomers

Isotropic and anisotropic magnetorheological elastomers (MREs) containing unmodified and silane modified iron sand particles in a natural rubber matrix were prepared. Tan δ and the amount of energy dissipated during cyclic deformation were used as the parameters to assess damping. Tan δ was measured through dynamic mechanical analysis over a range of frequency (0.01–130 Hz), strain amplitude (0.1–4.5%) and temperature (−100–50 °C). Energy dissipated was measured using a universal tester under cyclic tensile loading. The silane coupled improved the amount of energy dissipated during hysteresis tests as well as tan δ over the range of frequency and strain amplitude explored and tan δ increased with increasing magnetic field up to a saturation point at 600 mT. However, the presence of coupling agent and formation of different lengths of aligned particles did not strongly affect the value of Tg and maximum tan δ at Tg. Evidence from scanning electron microscopy (SEM) supported that the use of modified iron sand does not interfere with the formation of magnetic particles chains in the matrix during curing and the chains became longer and more aligned as the magnetic field strength increased.