Anisotropic Magnetorheological Elastomers Research Articles

Mechanical Properties Comparison of Isotropic vs. Anisotropic Hybrid Magnetorheological Elastomer-Fluid.

Magnetorheological (MR) materials are smart materials that can change their rheological characteristics when exposed to a magnetic field. Such rheological properties include viscosity and dynamic modulus. MR materials have emerged as one of the most efficient smart materials that can modify mechanical and viscoelastic characteristics. Depending on the medium used, MR materials can be classified into two types: magnetorheological fluids (MRFs) and magnetorheological elastomers (MREs). MREs are classified as isotropic or anisotropic based on CIP distribution inside the elastomer matrix. A unique hybrid material incorporating MRE and MRF is constructed in this work to investigate, compare, and the dynamic properties of isotropic, anisotropic, hybrid isotropic, and hybrid anisotropic MREs under various magnetic fields (0, 104, and 160.2 mT). The created samples are subjected to extensive testing, including static and dynamic evaluations. In the static tests, experiments use a compression linear displacement mode with a fixed maximum gap change of 3 mm. The temperature is maintained at a constant level of 24 °C throughout the 40 s test duration for each test, and the magnetic field is incrementally increased by varying the number of magnets, ranging from 0 to 160.2 mT for dynamic qualities using compression oscillations on a dynamic mechanical analyzer (DMA), including frequency and strain-dependent data. These experiments, carried out using sinusoidal shear movements, include an excitation frequency range of 0.1 Hz to 15 Hz while preserving, with a fixed shear strain of 2%.

Tensile Properties of Isotropic and Anisotropic Magnetorheological Elastomer With and Without Magnetic Field Application

In this study, two variations of magnetorheological elastomer (MRE) tensile specimens were fabricated, differing in their isotropic and anisotropic configurations. The isotropic MRE exhibited randomly dispersed carbonyl iron particle (CIP), whereas the anisotropic featured longitudinally aligned CIP particles along the gauge length of the tensile sample. The formation of the anisotropic MRE involved utilizing an electromagnetic curing chamber, which facilitated the alignment of CIP particles during the elastomer curing process. A mold was specifically designed to produce samples conforming to the dimensions outlined in ASTMD412-F. Subsequently, a Finite Element Method Magnetics (FEMM) analysis was conducted to examine the magnetic flux within the curing device for the anisotropic MRE. Uniaxial tensile tests were conducted on both MRE types, both in the absence and presence of a 30 mT magnetic field applied transversely to the direction of CIP alignment. Results indicated that without a magnetic field, the anisotropic sample exhibited a slightly higher tensile strength, lower elongation, and higher modulus at 100% strain. However, when a magnetic field was introduced, the isotropic sample demonstrated a more pronounced increase in tensile strength, showing an 18.4% improvement compared to the 5.6% increase observed in the anisotropic sample. Similar trends were observed in the reduction of elongation, with a 14% decrease for isotropic and a 7% decrease for anisotropic samples. Additionally, the data on modulus at a 100% strain revealed a 22.3% increase in stiffness for the isotropic sample, while the anisotropic sample showed a 10.6% increase.

Experimental characterization and fractional modelling of anisotropic magnetorheological elastomers under the influence of temperature and magnetic fields.

The multifaceted influence of combined variables on the mechanical-magnetorheological properties of isotropic and anisotropic MREs in a shear state is probed in this research. Specifically, the effects of preparation magnetic field, magnetic field intensity during rheometric testing, temperature, shear strain, angular frequency, and angle of structural matrix chains were examined. The viscoelastic properties of seven distinct MREs prepared in different pre-configuration settings were analysed by subjecting them to dynamic shear-rotational deformation at different temperatures and magnetic fields. A novel magneto-viscoelastic model was formulated for both isotropic and anisotropic MREs within the realm of linear viscoelasticity. The efficacy and robustness of this model were substantiated, offering a predictive framework for the materials' behavior. This comprehensive model explains the viscoelastic response of magnetorheological elastomers to shear loading, accounting for factors encompassing the preparation magnetic field, magnetic field intensity and temperature during testing, angular frequency, shear strain, and the orientation of the column-like matrix. Empirical findings underscored noteworthy trends, indicating that elevated temperatures led to a reduction in viscoelastic modulus, whereas increased magnetic field intensity resulted in its augmentation. Simultaneously, temperature and magnetic field intensification amplified the MR effect. Additionally, heightened preparation fields correlated with increased shear modulus, whilst variations in temperature and both magnetic fields induced noticeable changes in the Payne effect.

Magnetorheological effect and sensing performance of graphite sheet filled PDMS based magnetorheological elastomer under compression

In order to study the effect of large-sized graphite (Gr) sheet on the magnetorheological (MR) effect and sensing characteristics of MR elastomer (MRE), isotropic and anisotropic Gr-filled MRE samples with different carbonyl iron powder (CIP) contents were fabricated. The effect of Gr sheet on the microstructure, MR effect and sensing characteristics of the MRE samples were experimentally tested, and the mechanisms behind discussed. The results show that in the anisotropic MRE samples, the addition of Gr sheets results in the short particle chains formed between Gr sheets, thus leading to the high MR effect and low resistivity than those of isotropic counterparts. The non-monotonic resistivity responses of the Gr-filled MRE samples during compression were observed owing to the interlayer separation of Gr sheets and the reconstruction of conductive network. A higher piezoresistive response was observed from the isotropic Gr-filled MRE sample filled with the CIP content below the percolation threshold. The resistivities of the Gr-filled MRE samples decline with increasing the applied magnetic field. The isotropic sample filled with lower CIP content shows the higher magnetoresistive effect from the view point of absolute change in resistivity. While for the relative change in resistivity, the anisotropic sample filled with the higher CIP content has the higher magnetoresistive effect.

Enhanced viscoelastic magneto-mechanical properties for off-axis anisotropic magnetorheological elastomers: Experiment and modelling

In this study, the microstructure of tilt angle magnetic chains is adopted to construct off-axis anisotropic magnetorheological elastomers (MREs) for tailoring viscoelastic magneto-mechanical properties. The magnetorheological behaviour of anisotropic MREs is investigated using magneto-controlled smart devices to achieve dynamic mechanical response. The viscoelastic behaviour is modelled by fractional derivative (FDM) and extended Kelvin-Voigt model (EKVM), the viscoelastic properties of anisotropic MREs are characterized by experimental and theoretical methods. Meanwhile, a magneto-induced mechanical model is established to reveal the influence of the tilt angle of the magnetic chain, the prestrain, the mass fraction of carbonyl iron particles (CIPs), and the magnetic flux on the magneto-induced mechanical properties. First, the complex moduli of anisotropic MREs with 25% and 40% mass fractions containing 0°, 15°, and 25° magnetic chains were experimentally characterized under shear mode using excitation frequency (1–100 Hz) and flux densities (300mT). The nonlinear robustness method is used to identify the parameters of the storage modulus and loss modulus functions from the experimental results in the viscoelastic theoretical models. The error analysis of anisotropic MREs for complex moduli between the theoretical and experimental solutions is evaluated at different tilt angles and CIPs contents. Finally, magnetorheological tests on anisotropic MREs verified the theoretical results on the magneto-induced elastic modulus influenced by tilt angle, magnetic particle content and flux density. The description of the storage modulus in EKVM, with an error of less than 3%, is superior to that in FDM, with an error of less than 8.1% in the frequency domain. The loss modulus of anisotropic MREs in FDM for different tilt angles and mass fractions, was accurately evaluated at low frequency compared to the EKVM solution.

Properties and influence of magnetic fields on iron particles of anisotropic magnetorheological elastomers

The magnetorheological elastomer (MRE) is an intelligent material whose mechanical properties can be rapidly adjusted under a magnetic flux density. This material’s mechanical properties change due to the interaction between the iron particles inside the material. Understanding the influence of magnetic flux on iron particles in MRE materials is essential. Studies have proven that the distance and angle of inclination between iron particles significantly affect the magnetic flux density and the interaction force between the particles. Therefore, the distribution of iron particles substantially affects the material’s properties. However, understanding magnetic flux through magnetic particles is necessary to improve the material’s mechanical properties and to design magnetic field systems in systems using the materials. This study maps three problems affecting magnetic flux density to the properties of MRE. First, the mechanical characteristics of the MRE were presented in the frequency, amplitude, magnetic flux density, and magnetic flux inclination domains relative to the particle chain. Next, the influence of the magnetic flux on the particle chain was investigated based on the dipole interaction model and the magnetic force on iron particles. The finite element method also explored the magnetic flux distribution in the MRE material. Finally, the response of the single-degree-of-freedom damping system is tested experimentally. The results show that the influence of the magnetic flux on the iron particles in the MRE material is significant. The research results aim to improve the mechanical properties of MRE materials.

Microscopic double-chain sawtooth model and macroscopic four-parameter fractional-order derivative viscoelastic model based on magnetorheological elastomers

In order to restore the distribution of ferromagnetic particles in magneto-rheological elastomers to the greatest extent, the magnetotropic effect of magneto-rheological elastomers is more accurately represented, and the dynamic mechanical properties of magneto-rheological elastomers are more accurately reflected. In this paper, based on the dipole theory, a new microscopic model of magnetorheological elastomer, the double chain sawtooth model, is proposed based on the chain model and the main chain adsorption model, and a macroscopic viscoelastic mechanical model of magnetorheological elastomer, the four-parameter fractional order derivative improvement model, is proposed based on the classical macroscopic mechanical parametric model and the fractional order derivative model. A microscopic model of magnetorheological elastomer was combined with a macroscopic model to describe its mechanical properties. Isotropic and anisotropic magnetorheological elastomers with different mass fractions and different silicone oil contents were prepared using silicone rubber as the matrix and carbonyl iron powder as the filling phase, and dynamic shear tests were conducted to verify the validity of the model.

Magneto-mechanical properties of anisotropic magnetorheological elastomers with tilt angle of magnetic chain under compression mode

Characterization of mechanical properties of magnetorheological elastomers (MREs) is essential for the design of smart materials and devices with customized features and functionalities. While the properties of MREs under shear mode have been extensively researched, MREs with tilt angle under compression mode have been less exploited. In this study, a magneto-mechanical model of anisotropic MREs is established based on magnetic dipole theory and energy method considering the reconfiguration effect of compressive strain on the microstructure of the magnetic chain. This leads to the provision of a dynamic magneto-mechanical model of the anisotropic MREs, incorporating the magneto-induced mechanical model, by using the robust fitting method. Experiments were conducted to assess the force–deflection (stress–strain) characteristics of MREs with tilt angle under compression mode, subject to the regulation of the tilt angle of magnetic chain, magnetic flux density, and mass fraction of magnetic particles. The magnetic-induced modulus, obtained from the theoretical model, is experimentally verified through magneto-mechanical testing, alongside an analysis on the dynamic mechanical properties under different dynamic strain amplitudes and frequencies. The mean square error (MSE) in terms of magneto-mechanical storage modulus in the robust fitting ranges from 2.73% to 10.86%. Experimental results also show that the range of magneto-induced stress (typically from 178 KPa to 74.6 KPa) decrease when the tilt angle of the magnetic chain increases (from 15° to 25°) corresponding to 60% mass fraction. The compression strain of the anisotropic MREs, affecting both the spacing of adjacent magnetic particles and the tilt angle of magnetic chain, causes significant changes in the magnetic-induced modulus. In addition, the hysteresis loops under different deformation (Mullins effect) show an increasing energy dissipation with decreasing tilt angle.

Surface modification of carbonyl iron particles using dopamine and silane coupling agent for high-performance magnetorheological elastomers

Magnetorheological elastomers (MREs) are smart materials whose mechanical properties can quickly respond to changes in the external magnetic field. This phenomenon is known as the magnetorheological (MR) effect and is the key to the application of magnetorheological elastomers. Previous studies have found that the interface between magnetic particles and elastomers is a critical factor that influencing the MR effect of MREs. To improve the interfacial interaction between silicone rubber (SR) and carbonyl iron (CI) particles, in the MREs considered in this work, CI particles were subjected to surface modification through polydopamine (PDA) deposition and n-dodecyltrimethoxysilane (DTMS) grafting. X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) confirmed the successful deposition of PDA@DTMS coating layer with a thickness of about 30.6 nm. The tensile strength of anisotropic MREs increased by 31.5% after surface modification of CI particles. The study of magnetic field induced changes in viscoelastic properties showed that CI-PDA@DTMS based MREs exhibited a superior MR effect to the CI-based MREs.

Heat build-up and dynamic compressive behavior of anisotropic magnetorheological elastomer

Heat build-up and dynamic compressive behavior of anisotropic magnetorheological elastomer

Giant magnetostriction in low-concentration magnetorheological elastomers

Magnetorheological elastomers (MREs) are smart composite materials that can vary their mechanical properties under the influence of an external magnetic field. In the present work, we report the giant magnetostriction of low-concentration isotropic and anisotropic MREs, by combining a soft elastomer matrix with helicoidal-shaped particles. Magnetic characterization has shown high magnetic sensitivity of the anisotropic MREs near H ≅ 0, which can be up to 400% larger comparing to the isotropic counterparts. The determination of tensile elastic modulus (E) of the MREs indicates that the anisotropic samples become softer when the magnetic field is increased from H = 0 to H = 200 Oe. Due to the higher field sensitivity of the anisotropic composites, the magneto-induced elongation contributes to the increase in the overall strain when measuring the elastic modulus at low deformation. This compliance of the MRE explains the decrease in E from H = 0 to H = 200 Oe. Magnetostriction measurements were performed and giant strain values up to 3731 ppm were obtained for isotropic samples with 3.4 vol% of Hiperco particles under a field of H = 3500 Oe. This result stands out from the literature due to the giant induced elongation, with reduced volume fraction of particles. The developments of this work are a step forward on improving smart and efficient composites, that can have many applications, such as switches, controllable valves, and vibration attenuators.

Dynamic characterization of the magnetomechanical properties of off axis anisotropic magnetorheological elastomer

Abstract The use of magnetorheological elastomers in the mechanical and acoustic fields, by the automotive, aeronautical, and building industries, is currently developing strongly and rapidly. The perfect understanding of the capacity of smart insulation based on the absorption of the vibratory waves by magnetorheological elastomers materials passes by the knowledge of their dynamic mechanical behavior. In this present work, we have characterized the dynamic mechanical properties of the magnetorheological elastomer off axes anisotropy by the inclination, of different angles (15°, 30°, and 45°), of the pseudo-fibers of the iron particles formed by the application of a magnetic field at different intensities using an optimal loading rate of 30%. The rubber specimens were prepared by mixing micron-sized iron particles dispersed in room temperature vulcanized (RTV) silicone rubber by solution mixing. The experimental results obtained show a clear dependence of the effect of inclusion of ferromagnetic chains on the magnetomechanical properties. It is observed that the mechanical properties are better when applying a magnetic field of 0.6 T with an angle of inclination of 45°. The improvements added in this work could be useful in several industrial applications, such as automotive, aeronautic through adaptive control of damping and vibration level.

Effect of Cyclic Shear Fatigue under Magnetic Field on Natural Rubber Composite as Anisotropic Magnetorheological Elastomers.

With the development and wide applicability of rubber materials, it is imperative to determine their performance under various conditions. In this study, the effect of cyclic shear fatigue on natural-rubber-based anisotropic magnetorheological elastomer (MRE) with carbonyl iron particles (CIPs) was investigated under a magnetic field. An anisotropic MRE sample was prepared by moulding under a magnetic field. Cyclic shear fatigue tests were performed using a modified electromechanical fatigue system with an electromagnet. The storage modulus (G′) and loss factor in the absence or presence of a magnetic field were measured using a modified dynamic mechanical analysis system. Under a magnetic field, fatigue exhibited considerable effects to the MRE, such as migration and loss of magnetised CIPs and suppressed increase in stiffness by reducing the energy loss in the strain cycle. Therefore, the G′ of the MRE after fatigue under a magnetic field was lower than that after fatigue in the zero field. The performance of the MRE, such as absolute and relative magnetorheological effects, decreased after subjecting to cyclic shear fatigue. In addition, all measured results exhibited strain-dependent behaviour owing to the Payne effect.

Effect of lubrication on the mechanical behavior of magnetorheological elastomers in compression mode

The effect of the lubrication on the mechanical behavior of magnetorheological elastomers (MREs) in compression mode is experimentally studied. According to ISO 7743, there are two procedures to characterize specimens in compression mode. Differences in the properties of these materials between lubricated and non-lubricated conditions must be considered if devices such as vibration absorbers and isolators are to be developed. With lubrication, compression is said to be uniaxial and homogeneous, thus material properties can be obtained. Without lubrication, tests are easier to perform but results are strongly dependent on the piece shape. In this study isotropic and anisotropic MREs with iron particle volume concentrations of 10, 20, 30 and 40% are tested under different strain amplitudes, prestrain and magnetic fields for a frequency range up to 300 Hz, with and without lubrication. Important design parameters like amplitude, frequency and magnetic field dependency are showed to be dependent on lubrication.

Nanoparticle-Based Magnetorheological Elastomers with Enhanced Mechanical Deflection for Haptic Displays

Haptics allows tactile interactions between humans and digital interfaces. Magnetorheological elastomers (MREs) constitute a promising candidate material for creating the tactile interface of the future─one able to recreate 3D shapes that can be sensed with touch. Furthermore, an MRE formed by using nanoparticles, as opposed to previously used microparticles, is necessary to generate a variety of shapes involving sharp curvatures over small, micrometer-scale horizontal distances to pave the way for haptic displays with microtexture resolution. Here we fabricated both isotropic and anisotropic MREs with different concentrations (2-8 vol % nanoparticles) of soft, low-remanence ferromagnetic nanoparticles. When placed in a magnetic field gradient, isotropic MREs, nonintuitively, show higher deflection than anisotropic MREs, with the former achieving displacement on the order of a millimeter at just 100 mT. This enhanced performance in the isotropic case is explained based on the soft magnetic nature of the nanoparticles. We show that performance improves with magnetic content up to a composition of 6 vol %, where it plateaus. This behavior is attributed to the stiffness of the composite material increasing at a faster rate than the magnetization as the rigid magnetic nanoparticles are added to the elastomeric matrix. Moreover, 6 vol % microparticle-based isotropic and anisotropic MREs were fabricated and compared with the nanoparticle-based MREs. Anisotropic nanoparticle-based films show higher deflection when compared with their microparticle-based counterparts. The latter is only able to match the nanoparticle film deflection at higher applied fields of almost 300 mT. This performance difference between nanoparticle and microparticle-based films is attributed to the increased anisotropic film stiffness resulting from the larger micrometer-size particles. Finally, the optimally designed nanoparticle-based isotropic film was utilized to create a programmable and real-time reconfigurable braille-inspired interface.

Dynamic mechanical properties of magnetorheological polyurethane elastomers in comparison to existing antivibration rubbers

ABSTRACT This article primarily focused on dynamic mechanical analysis over a frequency range (0.1 to 140 Hz), temperature range (−100 to 50°C) and strain amplitude (0.1 to 5 percent). During hysteresis testing, the damping coefficient (Tanδ) and energy dissipation of isotropic and anisotropic magnetorheological elastomers with iron nanoparticles in a polyurethane rubber matrix to existing antivibration rubber were compared. Under tensile loading, energy dissipation was measured using universal testing. Different percentages of carbon black (CB) filler (30 phr, 50 phr and 70 phr) in a polyurethane matrix were selected for anti-vibration rubber comparison. During hysteresis testing, energy absorption has been found to be greater in CB Magnetorheological Elastomers(MREs) than in isotropic and anisotropic MREs, owing largely to the inclusion of CB in the formulation. CB additives were also tested on materials that were like anisotropic MREs. Relative comparative samples with the same percentage concentration of CB mixed with iron nanoparticles have greater damping characteristics and energy absorption. However, at the glass transition temperature (Tg), certain trends in energy absorption have shifted because segment flow motion of rubber chains has the greatest impact on energy absorption at glass transition temperature.

Development of New Phenomenological Models for Predicting Magnetic Permeability of Isotropic and Anisotropic Magneto-Rheological Elastomers

Designing smart devices based on magneto-rheological elastomers (MREs) is a quite challenging task due to the inherent nonlinear behavior of MREs in the presence of an applied magnetic field. In the early stage of the design process, the magnetic circuit parameters need to be optimized either via analytical approaches or FE simulations. These require a precise nonlinear magnetic permeability model (B-H curve formulation) of MREs. The model should consider the effect of essential design factors (particle volume fraction and anisotropy) and loading conditions (magnetic field and pre-strain). The main contribution of the present study is to formulate a field-dependent novel and reliable nonlinear B-H relation for MREs as functions of the basic design and loading factors. Three batches of isotropic and anisotropic MRE samples were fabricated with different particle volume fractions (15%, 30%, and 45%). Subsequently, a simple methodology was presented to determine the magnetic permeability and then the nonlinear B-H curves of the MREs considering wide variations in pre-strain (0, 12.5%, 25%, 37.5%, and 50%) as well as coil current, ranging from 0.2 A to 8 A. Experimental results showed that the relative magnetic permeability of both types of MREs increased with increasing pre-strain. Phenomenological-based models were consequently developed to estimate the nonlinear B-H curves of the isotropic and anisotropic MREs accurately and efficiently over the entire design and loading conditions considered. The proposed model can be effectively utilized for modeling and design optimization of MRE-based smart devices.

Manufacture and Reaction Replication of Unstructured and Restructured Elastomeric and Elastomeric Utilizing Steel Net

The magneto-rheological (MR) elastomeric material has developed addicted to a powerful and cutting-edge smart substance which adjusted and quickly acted upon in relations of mechanical belongingsusing or deprived of the usage of a magnetic flux. They are made of elastomeric materials with Feelements incorporated into the medium. Based on the application of a magnetic field during the fabrication process, isotropic and anisotropic MR elastomers are divided into various groups. An elastomer's matrix contains magnetizable particles that are distributed in a highly controlled and kind-organized manner. After observing the structural and behavioral alterations of MREs, another fabrication was made by layering a steel net between elastomeric mediums to replicate the behavior of MREs. Their performance was shown via a Fast Fourier Transform (FFT) analysis. Due to their exceptional mechanical properties, they can be used in a range of applications, including seismic devices, vibration absorbers, and isolators.

The influence of particle chain-magnetic field spatial location, frequency, dynamic strain amplitude and the prestrain on the mechanical performance of anisotropic magneto-rheological elastomer

Although there are literatures to characterize the properties of anisotropic magneto-rheological elastomer (MRE), more attention is paid when the particle chain is parallel to the applied magnetic field. However, in prospective of modeling and application design, mechanical characterization of anisotropic MRE under other particle chain-magnetic field spatial locations is needed. Herein, mechanical properties of anisotropic MRE with four kinds of particle chain-magnetic field spatial locations under varies frequencies, strain amplitudes and prestrains are tested. It shows that even the particle chain is perpendicular to the magnetic field, there exists an obvious MR effect. Besides the attraction of adjacent magnetized particles, the Maxwell stress tensor also contribute to the MR effect. Furthermore, an obvious strain amplitude dependent viscoelastic behavior is exhibited for anisotropic MRE. Moreover, the MR effect and the loss factor decrease as the increase of prestrain. The investigation contributes to the designing, modeling and applications of anisotropic MRE.

Declining Performance of Silicone-Based Magnetorheological Elastomers after Accelerated Weathering.

Magnetorheological elastomers (MRE)-based products are usually located in an area directly exposed to sunlight and rain. However, there is no specific research on the behavior of MRE after accelerated weathering. Therefore, in this study, the changes to the chemical and rheological properties of both isotropic and anisotropic MRE after accelerated weathering were examined. Treated and untreated specimens were compared. MRE specimens with 40% by weight CIP were prepared with no current excitation and another sample was prepared with 1.5 T of magnetic flux density. Each specimen was treated in an accelerated weathering machine, Q-Sun Xe-1 Xenon Test Chamber, under a UV light exposure cycle and water spray. A material characterization was carried out using FTIR and a rheometer to determine the changes to the chemical and rheological properties. The morphological analysis results showed that after the weather treatment, the surface was rough and more cavities occurred. The rheometer test results showed a significant decrease in the storage modulus of each treated MRE specimen, unlike the untreated MRE specimens. The decrease in the storage modulus value with currents of 0, 1, 2, and 3 Amperes was 66.67%, 78.9%, 85.2%, and 80.5%, respectively. Meanwhile, FTIR testing showed a change in the wave peak between the untreated and treated MRE specimens. Thermogravimetric analysis (TGA) also showed a decrease in MRE weight for each specimen. However, for both treated and untreated MRE specimens, the decrease in TGA was not significantly different. In all the tests carried out on the MRE samples, weather acceleration treatment caused significant changes. This is an important consideration for developers who choose silicone as the MRE matrix.