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The existing mold concept of fabricating magnetorheological elastomer (MRE) tends to encounter several flux issues due to magnetic flux losses inside the chamber. Therefore, this paper presents a new approach for enhancing particle alignment through MRE fabrication as a means to provide better rheological properties. A closed-loop mold, which is essentially a fully guided magnetic field inside the chamber, was designed in order to strengthen the magnetic flux during the curing process with the help of silicone oil (SO) plasticizers. The oil serves the purpose of softening the matrix. Scanning electron microscopy (SEM) was used to observe the surface morphology of the fabricated MRE samples. The field-dependent dynamic properties of the MREs were measured several ways using a rheometer, namely, strain sweep, frequency sweep, and magnetic field sweep. The analysis implied that the effectiveness of the MRE was associated with the use of the SO, and the closed-loop mold helped enhance the absolute modulus up to 0.8 MPa. The relative magnetorheological (MR) effects exhibited high values up to 646%. The high modulus properties offered by the MRE with SO are believed to be potentially useful in industry applications, particularly as vibration absorbers, which require a high range of stiffness.

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The widespread use of magnetorheological elastomer (MRE) materials in various applications has yet to be limited due to the fact that there are substantial deficiencies in current experimental and theoretical research on its microstructural durability behavior. In this study, MRE composed of silicon rubber (SR) and 70 wt% of micron-sized carbonyl iron particles (CIP) was prepared and subjected to stress relaxation evaluation by torsional shear load. The microstructure and particle distribution of the obtained MRE was evaluated by a field emission scanning electron microscopy (FESEM). The influence of constant low strain at 0.01% is the continuing concern within the linear viscoelastic (LVE) region of MRE. Stress relaxation plays a significant role in the life cycle of MRE and revealed that storage modulus was reduced by 8.7%, normal force has weakened by 27%, and stress performance was reduced by 6.88% along approximately 84,000 s test duration time. This time scale was the longest ever reported being undertaken in the MRE stress relaxation study. Novel micro-mechanisms that responsible for the depleted performance of MRE was obtained by microstructurally observation using FESEM and in-phase mode of atomic force microscope (AFM). Attempts have been made to correlate strain localization produced by stress relaxation, with molecular deformation in MRE amorphous matrix. Exceptional attention was focused on the development of molecular slippage, disentanglement, microplasticity, microphase separation, and shear bands. The relation between these microstructural phenomena and the viscoelastic properties of MRE was diffusely defined and discussed. The presented MRE is homogeneous with uniform distribution of CIP. The most significant recent developments of systematic correlation between the effects of microstructural deformation and durability performance of MRE under stress relaxation has been observed and evaluated.

Carbon-based particles, such as graphite and graphene, have been widely used as a filler in magnetorheological elastomer (MRE) fabrication in order to obtain electrical properties of the material. However, these kinds of fillers normally require a very high concentration of particles to enhance the conductivity property. Therefore, in this study, the nanosized Ni-Mg cobalt ferrite is introduced as a filler to soften MRE and, at the same time, improve magnetic, rheological, and conductivity properties. Three types of MRE samples without and with different compositions of Mg, namely Co0.5Ni0.2Mg0.3Fe2O4 (A1) and Co0.5Ni0.1Mg0.4Fe2O4 (A2), are fabricated. The characterization related to the micrograph, magnetic, and rheological properties of the MRE samples are analyzed using scanning electron microscopy (SEM), vibrating sample magnetometer (VSM), and the rheometer. Meanwhile, the effect of the nanosized Ni-Mg cobalt ferrites on the electrical resistance property is investigated and compared with the different Mg compositions. It is shown that the storage modulus of the MRE sample with the nanosized Ni-Mg cobalt ferrites is 43% higher than that of the MRE sample without the nanomaterials. In addition, it is demonstrated that MREs with the nanosized Ni-Mg cobalt ferrites exhibit relatively low electrical resistance at the on-state as compared to the off-state condition, because MRE with a higher Mg composition shows lower electrical resistance when higher current flow occurs through the materials. This salient property of the proposed MRE can be effectively and potentially used as an actuator to control the viscoelastic property of the magnetic field or sensors to measure the strain of the flexible structures by the electrical resistance signal.

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This study proposes the design and fabrication of a natural rubber-based magnetorheological elastomer (NR-MRE) engine mount as a new device in absorbing the vibration originated from the automotive engine. The conceptual design was performed through a simulation process by Finite Element Method Magnetics to analyze the magnetic field distribution. The simulation result had indicated that the device was capable of generating an equivalent magnetic field density of 0.31 T at the effective area. The MRE was prepared by utilizing 60 wt% of carbonyl iron particles (CIPs), and the cavity was filled by compression molding. The MRE compound was tested based on its basic mechanical properties, while the MRE engine mounts were tested under a static compression load at off- and on-state conditions. It was observed that the compound possessed a good tensile strength for a load bearer matrix with an average of 12.65 MPa. Subsequently, the results of the static compression load had showed that the MRE engine mounts recorded an increase of 12% in the force generated as compared to conventional engine mounts at an off-state condition. Meanwhile, at an on-state condition of 2.4 A, the MRE engine mounts recorded an increase in the force generated with 106%. The study has demonstrated that the proposed device can be one of the potential candidates for vibration control applications due to its stiffness controllability.

In this work, carbonyl iron particles (CIP) was grafted with polystyrene coating on its surface via polymerization method, and the coated-CIPs were then embedded into a silicone rubber with the ratio of 70:30 of CIP to silicone rubber in order to enhance the rheological properties of magnetorheological elastomer (MRE) in terms of lower initial storage modulus and higher MR effect. By using field emission scanning electron microscopy (FESEM) that is equipped with the energy dispersive X-ray spectroscopy for elemental analysis, it was observed that elements of C, N, O, Si, Fe, Br, Cu, and Sn were detected, confirming that the coating layer has been successfully developed on the CIP.Additionally, the investigation of the rheological characteristics was conducted at 25 C with three different sweep conditions using rheometer MCR 302.Firstly the strain amplitude was swept from 0.001% to 10% strain with 1 Hz frequency. Then, the frequency was varied from 1 Hz to 100 Hz under 0.01% strain at an applied current of 0-5 A. Lastly, the current was swept from 0 to 5 A under 0.01% strain amplitude and 1 Hz excitation frequency. It was discovered that the storage modulus of the polystyrene-coated CIP MRE is lower than that of uncoated-CIP MRE in all three sweep profiles. Advantageously, the magnetorheological (MR) effect of the coated-CIP MRE sample is higher than that of the uncoated-CIP MRE by 28.04%. Moreover, it was found that the coated-CIP MRE exhibited higher damping behavior with more than 0.14 loss factor than 0.12 loss factor of the uncoated sample. The dimensional stability of polystyrene coating on the CIP was an attributing factor to this enhanced damping behavior of the coated-CIP MRE. Thus, it became clear that the polystyrene-coated CIP embedment in MRE is more desirable than that of MRE with uncoated CIP.