Magnetorheological Composites Research Articles

Experimental and theoretical investigation on magnetorheological elastomers containing carbonyl iron particles coated with silane coupling agent

Magnetorheological (MR) elastomer composites, comprising soft silicone rubber, various additives, and different weight fractions of carbonyl iron particles (CIPs) coated with silane coupling agent, are produced via a novel manufacturing process in an anisotropic state. This study encompasses both experimental and modeling investigations into the dynamic viscoelastic properties of magnetorheological elastomer (MREs) in shear mode under varying magnetic fields, displacement amplitudes, and frequencies. Two MRE vibration mitigation devices are fabricated to experimentally assess the shear storage modulus and the loss factor of MREs. The experimental findings reveal a pronounced MR effect in the MRE devices, where both the shear storage modulus and the loss factor increase with rising magnetic fields, frequencies, and particle weight fractions, yet decrease with higher displacement amplitudes. A modified fractional-derivative equivalent parametric model, grounded in a magnetic field- and frequency-dependent shear modulus model along with internal variable theory, is proposed to describe the effects of these key influencing factors on the MREs’ dynamic viscoelastic properties. Comparative analysis of experimental and numerical data demonstrates that this refined mathematical model can accurately represent the dynamic viscoelastic properties of MREs.

Adjusting dynamic and damping performance in fiber-reinforced magnetorheological elastomer composite conical shells subjected to compressive loads

This study explores the dynamic behavior of axially loaded conical shells composed of magnetorheological elastomer composites (MRECs). The investigation focuses on analyzing the impact of compressive loads on the frequencies and loss factors of these composites. The MRECs consist of laminates reinforced with fibers, enabling tunable viscoelastic properties through the utilization of magnetic fields. The equivalent mechanical characteristics of the MREC are calculated using the modified Voigt and Halpin–Tsai micromechanical rules. By employing the first-order shear deformation theory and Sanders-based strains, the kinematics of the conical shell are accurately modeled. A semi-analytical analysis, combining trigonometric expansion and the generalized differential quadrature (GDQ) methods, is employed to solve the system's highly coupled partial differential equations. Two consecutive analyses are performed. Firstly, the critical buckling load of the MREC conical shell is obtained through a stability analysis. Subsequently, the frequencies and loss factors of the shell in the pre-buckling zone are computed. Parametric analyses are conducted to study the impact of key factors, including magnetic field strength, compressive load magnitude, composite properties, geometric parameters, and boundary conditions. The proposed methodology is rigorously validated through meticulous accuracy and convergence analysis. The outcomes provide valuable insights into the dynamic response of axially loaded magnetorheological elastomer composite conical shells, highlighting their potential in adjustable dynamic and damping systems.

Tuning damping and dynamic response of smart MR cylindrical composite panels based on a higher-order shear deformation theory

This study delves into the dynamic analysis of magnetorheological elastomer composite (MREC) cylindrical panels with laminated construction. Magnetorheological elastomers (MREs) are viscoelastic materials that exhibit tunable properties when subjected to magnetic fields. By incorporating reinforcing fibers, a new class of materials, MRE Composites (MRECs), is formed, which not only inherits MRE properties but also enhances rigidity. The novelty of the present study resides in its comprehensive exploration of the vibration and damping characteristics inherent in deep laminated cylindrical shells composed of MRECs. The homogenization of this composite media is performed by employing the modified rule of mixture and Halpin-Tsai micromechanical rule. To achieve this, the Mechab theory, utilizing a high-order hyperbolic function, approximates the displacement field. The study employs the generalized Maxwell's constitutive model to describe the viscoelastic behavior of MRECs, and Hamilton's principle is used to derive the partial differential form of vastly coupled equations of motion. The 2-dimensional Chebyshev collocation method, a discretization method, is applied to solve these equations, allowing the determination of natural frequencies and loss factors. The investigation covers various parameters, including magnetic field strength, volume fraction of reinforcers, layering, and fiber angles, geometry, and boundary conditions, to understand their influence on the dynamic response of MREC cylindrical panels. The results provide valuable insights into the potential applications of these tunable materials in adjustable dynamic and damping systems, contributing to advancements in solid mechanics and materials engineering. Such knowledge opens up new possibilities for utilizing MRECs in diverse technological applications.

A novel parametric model for nonlinear hysteretic behaviours with strain-stiffening of magnetorheological gel composite

Magnetorheological (MR) gels are a new class of MR composite materials that can effectively address the issue of particle agglomeration in MR fluids, enhancing the controllability of materials in engineering applications. In this study, a novel parametric model was developed to track the nonlinear hysteretic behaviours with strain-stiffening of the MR gel. The model parameters were identified using the measurement data pertaining to five current levels (0A, 0.2A, 0.5A, 0.8A, and 1A) under a strain amplitude of 10% and a frequency of 0.1 Hz. The fruit fly optimisation algorithm (FOA) was used to determine the optimal solution for the model parameters. The model parameters were generalised with respect to the loading current, and the reliability of the generalised model was verified. The results of the study demonstrate that the proposed model outperforms two classical models, the Bouc–Wen model and viscoelastic–plastic model, in capturing the nonlinear and strain-stiffening behaviour of MR gels, particularly for higher current excitations. This study has potential applications in predicting the nonlinear hysteresis behaviour of automotive dampers, and provides a theoretical basis for the semi-active control of suspensions.

Performance Analysis of Magnetorheological Porous Fabric Composite

In this paper, magnetorheological (MR) porous fabric composites were prepared by using non-woven fabrics pretreated with lithium stearate. Due to the porous structure of non-woven fabric and the good stability of lithium stearate, the mechanical properties and sedimentation stability of the composite have been improved. The viscosity, shear stress and dynamic viscoelasticity of different samples were analyzed by rheological properties tests. The results indicate that the mechanical properties of the composite samples containing lithium stearate are improved compared with the MRF (magnetorheological fluid) sample, and its sedimentation stability under non-working conditions is also improved. However, with the increase of lithium stearate content, the improving effect of material performance gradually decreased. The experimental results show that when the magnetic flux density is 0.31 T, the shear stress of the MR porous fabric composite with 1 wt% lithium stearate is about 27 kPa, which increases by 51.1% compared with the MRF sample.

Strain dependent magneto-mechanical property of magnetorheological gel composite: Rheological measurement and model establishment

Controlled over an external magnetic field, rheological response of magnetorheological gel (MRG), a smart composite that could change according to a specific stimulation, could be reversible and adjustable. This paper sheds light on the large deformation-dependent magneto-mechanical property of MRG under different working mode, i.e. quasi-static and dynamic mode, which has rarely been systematically analyzed and compared. The viscoelastic and hysteretic properties of MRG were evaluated by three kinds of experiments that were conducted under different strain excitations—linearly monotonic and cyclic strain, and harmonically cyclic strain. The results reveal that shear stress and normal stress display opposite trend with the increase of strain under quasi-static monotonic loading. A simple parametric model is proposed to describe the shear stress of MRG under quasi-static loading. Furthermore, for quantitatively characterizing the Payne effect of MRG under dynamic loading, the classical Maier-Goritz model predicting the Payne effect of material was modified by introducing a magnetic dipole theory that considers the effect of magnetic field on Payne effect. The magnetic dipole theory is established based on triangular double-chain rather than the conventional single chain. Moreover, in the presence of a magnetic field, the hysteretic loop of MRG would occur a overshoot phenomenon under dynamic working mode, which could not been found under quasi-static cyclic mode. Also, dynamic loading, compared with quasi-static one, could enable MRG to dissipate more energy. This paper is possibly conducive to understanding the working mechanisms about microstructures of MRG and designing MRG-based vibration control devices.

Attenuation and rheological analysis of magnetic field-induced responsiveness for the magnetorheological elastomer-based composite

A novel self-supporting multi-layer magnetorheological elastomer-based (MRE-based) composite with large magnetic field-induced responsiveness has been designed and fabricated. We characterized its morphological properties, evaluated the impact of fabrication conditions on its field-induced responsiveness, investigated attenuation of its field-induced responsiveness under different storage temperatures along with time and analyzed this mechanism from the perspective of rheology. The results showed that the MRE-based composite had homogeneous dispersing of the magnetic fillers and a clear interface between different layers. The field-induced responsiveness of the MRE-based composite could be affected by the fabrication conditions, and it attenuated at different rates when subjected to different storage temperatures along with time; its attenuation period lasted a few days under room temperature while over one month under low temperature (4 °C). The rheological analysis results indicated a long-term cross-linking process over the storage period along with the attenuation of field-induced responsiveness, which might lead to increasing elasticity (indicated by the loss factor tan δ) and rigidity (indicated by the storage modulus G′) of the MRE-based composite along with the storage period. What’s more, emerging feature of Payne effect could be found on MRE-based composite during cyclic shear, which indicated decline of the mechanical properties due to strain-induced inherent friction. On the other hand, the iron fillers in MRE layer could enhance the shear modulus and lead to MR effect (up to 187%) for the whole composite, which benefits to the magnetic field-induced responsiveness, due to the relative strengthen of the MRE layer against the assist layer. This work presents a better understanding on the attenuation of the field-induced responsiveness, which is important for the future application of the MRE-based composite.

The Influence of Self-Heating Iron on the Thermal, Mechanical, and Swelling Properties of PDMS Composites for Organic Solvents Removal.

Volatile organic compounds pollute the environment and pose a serious threat to human health due to their toxicity, mutagenicity, and carcinogenicity. In this context, it is highly desirable to fabricate high-performance poly (dimethylsiloxane) (PDMS) composites to remove organic solvents from the environment using a simple technique. Therefore, in the present study, Fe-PDMS composites were fabricated using a technique based on magnetic induction heating with iron particles serving as a self-heating agent. Under an alternating magnetic field, the iron particles served as a thermal source that assisted in the progression of PDMS crosslinking. The influence of self-heating iron on the properties of the fabricated Fe-PDMS composites was also investigated. The hydrosilation reaction occurring during the crosslinking process was controlled using FT-IR. The heating efficiency of PDMS 1, PDMS 2, and PDMS 3 was studied as the function of induction time (0–5 min) and the function of iron content (0%, 1%, and 30% wt.%). The results revealed that the mechanical properties of the PDMS 2 composite were enhanced compared to those of the PDMS 1 and PDMS 3 composites. The mechanical properties of PDMS 3 were the least efficient due to cluster formation. PDMS 3 exhibited the highest thermal stability among all composites. Furthermore, the swelling behavior of different materials in various organic solvents was studied. PDMS was observed to swell to the greatest extent in chloroform, while swelling to a large extent was observed in toluene, pentane, and petroleum ether. PDMS swelling was the least in n-butanol. The elastomeric behavior of crosslinked PDMS, together with its magnetic character, produces stimuli-responsive magneto-rheological composites, which are quite efficient and suitable for applications involving the removal of organic solvents.

Living magnetorheological composites: from the synthesis to the in vitro characterization

A new type of magnetorheological (MR) material is reported that brings together conventional MR composites (MRCs) and biomaterials. Living MRCs based on carbonyl iron microparticles (CIPs) as magnetoactive filler, sodium alginate as elastomer and cells as biological components were prepared and characterized. The effect of CIPs concentration in isotropic alginate composites was examined by using thermogravimetric analysis, infrared spectroscopy, swelling and degradation tests in culture medium (Dulbecco’s Modified Eagle’s Medium, DMEM). To self-assemble the CIPs within the polymer matrix, the cross-linking process took place under an external magnetic field (24 mT). The cytotoxicity experiments were performed with human mesenchymal stem cells and human fibroblasts loaded inside of the hydrogel. It was demonstrated that the living MRCs supported cell survival and proliferation. The rheological response of the MRCs was evaluated in dynamic oscillatory tests in the absence and presence of magnetic fields. The viscoelastic response of the living MRCs improved when a magnetic field was applied. This work demonstrates the possibility to use CIPs in the fabrication of living composites with MR response. Results could be of interest in smart biomedical applications.

Magnetostriction-based force feedback for robot-assisted cardiovascular surgery using smart magnetorheological elastomers

Magnetorheological elastomer composites are a class of smart materials with controllable deformation by an external magnetic field. Recent studies have shown the feasibility of using magnetorheological composites for tactile feedback applications. In this study, a new haptic feedback system for regulating torque through contact friction was proposed, constitutively modeled, and experimentally validated. To this end, an analytical constitutive model for the composite was proposed and solved and was used to find the contact stress between the composite and a ferromagnetic shaft. Afterward, the proposed device was prototyped and a series of validation studies with three types of magnetorheological composites was performed. The validation studies showed that the analytical predictions for resistant torque were in fair agreement with the experimental results. Also, the proposed device was capable of generating and controlling a resistant torque of up to 115.5±0.7 mNm and haptic force of up to 5.77 N. The system showed favorable performance for haptic feedback applications in robot-assisted cardiovascular interventions.

Hybrid magnetic elastomers prepared on the basis of a SIEL-grade resin and their magnetic and rheological properties

Abstract Hybrid magnetic elastomers (HMEs) belong to a novel type of magnetocontrollable elastic materials capable of demonstrating extensive variations of their parameters under the influence of magnetic fields. Like all cognate materials, HMEs are based on deformable polymer filled with a mixed or modified powder. The complex of properties possessed by the composite is a reflection of interactions occurring between the polymer matrix and the particles also participating in interactions among themselves. For example, introduction of magnetically hard components into the formula results in the origination of a number of significantly different behavioral features entirely unknown to magnetorheological composites of the classic type. Optical observation of samples based on magnetically hard filler gave the opportunity to establish that initial magnetization imparts magnetic moments to initially unmagnetized grains, as a result of which chain-like structures continue to be a feature of the material even after external field removal. In addition, applying a reverse field causes them to turn into the polymer as they rearrange into new ring-like structures. Exploration of the relationship between the rheological properties and magnetic field conducted on a rheometer using vibrational mechanical analysis showed an increase of the relative elastic modulus by more than two orders of magnitude or by 3.8 MPa, whereas the loss factor exhibited steady growth with the field up to a value of 0.7 being significantly higher than that demonstrated by elastomers with no magnetically hard particles. At the same time, measuring the electroconductivity of elastomers filled with a nickel-electroplated carbonyl iron powder made it possible to observe that such composites demonstrated an increase of variation of the resistivity of the composite influenced by magnetic field in comparison to elastomers containing untreated iron particles. The studies conducted indicate that this material exhibits both magnetorheological and magnetoresistive effect and does indeed have the potential for use in various types of devices.

Hybrid Magnetorheological Composites for Electric and Magnetic Field Sensors and Transducers.

We present a simple, low-cost, and environmental-friendly method for the fabrication of hybrid magnetorheological composites (hMCs) based on cotton fibers soaked with a mixture of silicone oil (SO), carbonyl iron (CI) microparticles, and iron oxide microfibers (F). The obtained hMCs, with various ratios () of SO and F, are used as dielectric materials for manufacturing electrical devices. The equivalent electrical capacitance and resistance are investigated in the presence of an external magnetic field, with flux density B. Based on the recorded data, we obtain the variation of the relative dielectric constant (), and electrical conductivity (), with , and B. We show that, by increasing , the distance between CI magnetic dipoles increases, and this leads to significant changes in the behaviour of and in a magnetic field. The results are explained by developing a theoretical model that is based on the dipolar approximation. They indicate that the obtained hMCs can be used in the fabrication of magneto-active fibers for fabrication of electric/magnetic field sensors and transducers.

Tunability of Band Gaps in Two-Dimensional Phononic Crystals with Magnetorheological and Electrorheological Composites

The elastic wave propagation properties of phononic crystals (PnCs) composed of an elastic matrix embedded in magnetorheological and electrorheological elastomers are studied in this paper. The tunable band gaps and transmission spectra of these materials are calculated using the finite element method and supercell technology. The variations in the band gap characteristics with changes in the electric/magnetic fields are given. The numerical results show that the electric and magnetic fields can be used in combination to adjust the band gaps effectively. The start and stop frequencies of the band gap are obviously affected by the electric field, and the band gap width is regulated more significantly by the magnetic field. The widest and highest band gap can be obtained by combined application of the electric and magnetic fields. In addition, the band gaps can be moved to the low-frequency region by drilling holes in the PnC, which can also open or close new band gaps. These results indicate the possibility of multi-physical field regulation and design optimization of the elastic wave properties of intelligent PnCs.

Synergistic improvement of mechanical and magnetic properties of a new magnetorheological elastomer composites based on natural rubber and powdered waste natural rubber glove

Abstract Recycling of rubber waste and finding the effective methods to extend its use are one of major challenges nowadays. In the present study, waste natural rubber glove (wNRg) was used in an attempt to extend its use and create a value-added composite based on natural rubber (NR) and wNRg. Another interesting focus was to develop such material into a new Magnetorheological Elastomer (MRE). This MRE can be prepared by incorporating Ferromagnetic particles namely carbonyl iron (CI) to the rubber composite. Carbon black (CB) was also added to obtain MRE with remarkably mechanical properties. CI was fixed at 60 phr where the CB was varied from 10 – 30 phr. Higher thermal conductivity and magneticity in nature of CI had made the composites faster cure and higher magnetic strength. On the contrary, superior tensile strength, modulus and elongation at break were found in the presence of CB. From the experimental results, hybridization of 60/10 phr/phr of CI and CB is highly suggested to gain the synergistic strength and magneticity. This is expected to solve a big problem in the application of MRE.

Effects of Filler Distribution on Magnetorheological Silicon-Based Composites.

The smart materials subclass of magnetorheological elastomer (MRE) composites is presented in this work, which aimed to investigate the influence of filler distribution on surface morphology. Iron particles with sizes ranging from 20 to 150 µm were incorporated into the elastomer matrix and a 30% volume fraction (V%) was chosen as the optimal quantity for the filler amount in the elastomer composite. The surface morphology of MRE composites was examined by 3D micro-computed tomography (µCT) and scanning electron microscopy (SEM) techniques. Isotropic and anisotropic distributions of the iron particles were estimated in the magnetorheological elastomer composites. The filler particle distribution at various heights of the MRE composites was examined. The isotropic distribution of filler particles was observed without any influence from the magnetic field during sample preparation. The anisotropic arrangement of iron fillers within the MRE composites was observed in the presence of a magnetic field during fabrication. It was shown that the linear arrangement of the iron particle chain induced magnetization within the composite. Simulation analysis was also performed to predict the particle distribution of magnetization in the MREs and make a comparison with the experimental observations.

Scanning Probe Microscopy of Magnetorheological Elastomers

The shape and size distribution of micro- and nanoscale particles of a magnetoactive filler in an elastomeric matrix on the surface of a magnetorheological composite are determined by SEM and AFM methods. With the aid of AFM, the phenomena of the restructuring of particles of filler aggregates on the surface of elastomers under the action of a weak external constant magnetic field are directly visualized. A model is proposed for the interaction of the magnetoactive filler with the elastomeric matrix of a composite, which explains the observed experimental results.

Study of filler microstructure in magnetic soft composites

Electron and atomic force microscopy were used for the study of magnetoactive filler surface microstructure in a magnetorheological composite. The particles redistribution phenomena of filler aggregates on the surface of elastomers under the action of a small external applied constant magnetic field are visualized. A model is proposed for the interaction of a magnetoactive filler with an elastomeric matrix of the composite, which explains the observed experimental results.

Villari effect in silicone/FeGa composites

This paper presents the results of the Villari effect study in FeGa magnetorheological composites with very low stresses. The composites consist of a silicone matrix and Fe75Ga25 powder of size ranging from 50 to 100 $$\upmu \hbox {m}$$ . Two types of composites, one is with 45 wt% and the other one with 30 wt% of Fe75Ga25 powder have been manufactured. The Villari effect has been measured in both samples as-manufactured and in those in which a 1 T magnetic field has been applied after curing. The results indicate that the composites with an applied field of 1 T after curing show the greatest Villari signal even without any applied magnetic field. This fact allows a design of a low-cost force sensor and high performance. A simple model, based on the change in the cross-section of the composite, has been developed to explain the results obtained.

Reinforced, Extruded, Isotropic Magnetic Elastomer Composites: Fabrication and Properties

The study involves the development of isotropic magnetorheological elastomer composites (i-MREs) with improved mechanical properties, their preparations, and properties characterizations. The novelty of the research is the use of extrusion process in the preparation of composites containing two different fillers: carbonyl iron powder (CIP) as magnetic filler and carbon black (FEF, N550) as reinforcing one. So far, the process of extrusion has been used to prepare magnetic composites without filler that improve mechanical properties. It is worth mentioning that the polymer matrix (ethylene-octene copolymer, EOR) offers excellent performance in extrusion applications. In this research, two methods of magnetic composites preparation were reported: traditional, during two-roll mill, and a new one using extrusion process. It was found that the usage of new processing technology allowed forming more homogenous dispersion of particles in elastomer matrix and oriented polymer chains, resulting in an improved rheometric characteristic, increased crosslink density, and decrease of the storage modulus (Payne effect). Based on both static/dynamic mechanical properties and damping properties under the influence of compression stress, the positive influence of extrusion process on material characteristics was confirmed. Moreover, all composites proved very good magnetic properties and resistance to thermooxidative ageing.

The Magneto-Mechanical Behavior of Active Components in Iron-Elastomer Composite

The magneto-rheological effects in iron-elastomer composites (IEC) were investigated by simulation, surface topography, and 3D representation. The simulated behavior of magneto-rheological elastomeric composites in the presence of an external magnetic field was determined and the influence of magnetic intensity on the isotropic distribution of iron filler particles in IECs was investigated. The magnetic intensity distribution was analyzed from the edge of the surface towards the center of the IEC. The samples were characterized for microstructural images after experimental tests using both micro-computed tomography (µCT) and scanning electron microscopy (SEM). The adhesion of filler particles within the matrix of the magneto-rheological elastomer (MRE) composite and their distributions were also investigated. µCT showed the overall 3D representation of IEC and the inner distribution of filler particles revealed the presence of some porosity which may be due to bubbles and voids in the matrix of the composite. Finally, a mechanism was established governing particle–particle interactions on the basis of dipole–dipole interactions.