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The characteristics and behaviors of magnetorheological elastomer (MRE) within the elastic region are significantly important to demonstrate potentiality toward infinitesimal deformation in various applications. As MRE dynamically shears within an elastic region at constant small deformation, its significant consequence has long been a pending topic, hampered partly by the lack of empirical evidence. Therefore, this paper aimed to investigate the onset microscopically transformation of the MRE sample precipitated to storage modulus behavior under stress relaxation conditions. To achieve the aim, MRE with 70 wt% carbonyl iron particles was dynamically sheared at 1 Hz frequency and 0.01% strain for a designated period of test duration. The morphology evaluation of the sheared sample disclosed the development of permanent microplasticity in a very narrow region of shear bands. The deformation adequately reduced the storing energy ability of the MRE at a dominantly elastic behavior. The results revealed that the ability of MRE to store deformation energy slightly reduced by 0.3%–0.5% for the 2000 s test interval. This interesting onset phenomenon was successfully achieved, and the establishment of this early-stage deformation was undeniably important as preliminary data for catastrophic investigation at a longer duration. [ABSTRACT FROM AUTHOR]

Magnetorheological (MR) foam, which is comprised of magnetic particles inside the matrix phase, is capable of changing its physical and rheological properties corresponding to the applied magnetic field. However, the performance of this material seems unsatisfactory due to the nonuniform distribution of magnetic particles throughout the composite area resulting in uneven magnetic properties. Since uniform magnetic properties are significant regarding MR foam, in situ fabrication using a polyvinyl chloride mould can be used to achieve the targetted improvement. MR foam was prepared with various amounts of carbonyl iron particles (CIPs), 0, 35, 45 and 55 wt%, and investigated at three different positions (top, middle and bottom parts) with a vibration sample magnetometer. The results showed that the hysteresis loop at all CIP concentrations of 35, 45 and 55 wt% exhibited superparamagnetic properties with magnetic saturation. The Ms of the top, middle and bottom positions were almost the same with a small standard deviation below 2 Am2 kg–1. Moreover, it is observed that the effect of porosity results in the enhancement of the magnetic saturation and remanence values. These results reveal the promising uniform magnetic properties of MR foam, which can benefit the industry by helping produce a consistent MR foam. [ABSTRACT FROM AUTHOR]

This study focused on the effect of manganese substituted cobalt ferrite (MnxCo1–xFe2O4) nanoparticles with different mole ratios (x = 0, 0.25 and 0.5) in magnetorheological fluids (MRF). The nanoparticles were synthesized using co-precipitation method. The irregularly–spherical form of the nanoparticles was observed/confirmed using a field emission scanning (FESEM) microscope. The vibrating sample magnetometer (VSM) was performed to analyze the effect of nanoparticles in MRF on their magnetic properties. The VSM test results show that the nanoparticles have a negative effect on the magnetic properties of MRF. The higher magnetic saturation of nanoparticles will reduce more magnetic saturation in MRF. This phenomenon shows that the direction of the magnetic field from the cobalt manganese ferrite has the opposite direction to MRF. It is also identified that the field-dependent rheological properties of MRF show that the addition of nanoparticles increases the yield stress of MRF results except for Mn0.5Co0.5Fe2O4 which leads to the reduction of the yield stress of MRF. [ABSTRACT FROM AUTHOR]

In this study, magnetorheological elastomer (MRE) was fabricated using an electromagnetic device with a new configuration mold at the orientation of 0°, 45° and 90°. This new curing concept enhanced the alignment of carbonyl iron particles (CIPs) within the silicone matrix in the presence of silicone oil (SO) during solidifying, by eliminating air gaps to prevent magnetic flux losses. Using a mold made of steel, which is a magnetic material, the mold functions as a guide for concentrated magnetic flux of 0.315 T to pass through the MRE sample. Scanning electron microscopy (SEM) was used to observe the surface morphology of the fabricated MRE samples particularly the alignment of the CIPs. The field-dependent dynamic properties of the MREs were measured using a rheometer. The analysis implied that the effectiveness of the MRE operating under shear deformation with this curing concept provided the highest magneto-induced modulus of 1.01 MPa when a 45° orientation mold is used, with relative magnetorheological (MR) effect value up to 918%, followed by 0° mold orientation with 0.79 MPa magneto-induced modulus and 646% relative MR effect. The high modulus properties offered by this MRE are believed to be potentially useful in industrial applications where a high range of stiffness is required particularly in the shear direction. [ABSTRACT FROM AUTHOR]

Magnetorheological (MR) material is a type of magneto-sensitive smart materials which consists of magnetizable particles dispersed in a carrier medium. Throughout the years, coating on the surface of the magnetic particles has been developed by researchers to enhance the performance of MR materials, which include the improvement of sedimentation stability, enhancement of the interaction between the particles and matrix mediums, and improving rheological properties as well as providing extra protection against oxidative environments. There are a few coating methods that have been employed to graft the coating layer on the surface of the magnetic particles, such as atomic transfer radical polymerization (ATRP), chemical oxidative polymerization, and dispersion polymerization. This paper investigates the role of particle coating in MR materials with the effects gained from grafting the magnetic particles. This paper also discusses the coating methods employed in some of the works that have been established by researchers in the particle coating of MR materials. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The diverse applications of magnetorheological elastomer (MRE) drive efforts to understand consistent performance and resistance to failure. Stress relaxation can lead to molecular chain deterioration, degradation in stiffness and rheological properties, and ultimately affect the life cycle of MRE. However, quantifying the energy and molecular dynamics during stress relaxation is challenging due to the difficulty of obtaining atomic-level insights experimentally. This study employs molecular dynamics (MD) simulation to elucidate the stress relaxation in MRE during constant strain. Magnetorheological elastomer models incorporating silicone rubber filled with varying magnetic iron particles (50-80 wt%) were constructed. Experimental results from an oscillatory shear rheometer showed the linear viscoelastic region of MRE to be within 0.001-0.01% strain. The simulation results indicated that stress relaxation has occurred, with stored energies decreased by 8.63-52.7% in all MRE models. Monitoring changes in energy components, the highest final stored energy (12,045 kJ) of the MRE model with 80 wt% Fe particles was primarily attributed to stronger intramolecular and intermolecular interactions, revealed by higher potential energy (3262 kJ) and van der Waals energy (- 2717.29 kJ). Stress relaxation also altered the molecular dynamics of this MRE model as evidenced by a decrease in kinetic energy (9362 kJ) and mean square displacement value (20,318 Å 2 ). The MD simulation provides a promising quantitative tool for elucidating stress relaxation, preventing material failure and offering insights for the design of MRE in the nanotechnology industry., (© 2024. The Author(s).)

It is well known in the field of materials science that a substance's longevity is significantly influenced by its environment. Everything begins with the initial contact on a material's surface. This influence will then deteriorate and have an extended negative impact on the strength of the material. In this study, the effect of natural weathering in tropical climates on magnetorheological elastomer (MRE) was investigated through microstructural evaluation to understand the aging behavior of the environmentally exposed MRE. To understand and elucidate the process, MREs made of silicone rubber and 70 wt% micron-sized carbonyl iron particles were prepared and exposed to the natural weathering of a tropical climate for 90 days. The MRE samples were then mechanically tensile tested, which revealed that Young's modulus increased, while elongation at break decreased. Surface degradation due to weathering was suspected to be the primary cause of this condition. Using scanning electron microscopy (SEM), the degradation of MRE was investigated as a function of morphological evidence. Upon examination through SEM, it was noted that the weathering effects on the morphology of the exposed samples showed distinct characteristics on the degraded surfaces of the MRE, including numerous microvoids, cavities, and microcracks. While these features were not prominent for the MRE itself, they bear resemblance to the effects observed in similar materials like rubber and elastomer. An atomic force microscope (AFM) is used to investigate the surface topography and local degradation conditions. This observation revealed a distinctive degradation characteristic of the MRE in connection to natural weathering in tropical climates. The surface damage of the MRE samples became severe and inhomogeneous during the environmental aging process, and degradation began from the exposed MRE surface, causing the mechanical characteristics of the MRE to significantly change., (© 2024. The Author(s).)

This paper aims to investigate the mechanical and rheological properties of magnetorheological elastomer (MRE) in marine ecosystems. The prepared samples comprised silicone rubber (SR) and 70 wt% micron-sized carbonyl iron particles (CIPs), immersed in an artificial marine ecosystem using salt water (Natrium Chloride) for 30 days. The mechanical properties of MRE samples were evaluated using hardness and quasi-static tensile tests. While the rheometer was used to investigate the rheological properties of their storage modulus condition with magnetic field stimulation. Further analysis of the defects and damages caused by salt water ageing was done through morphological observation using scanning electron microscope (SEM) technology. The results showed that the hardness and tensile strength of MRE samples that were soaked in salt water were affected over time. Lower values of hardness and tensile strength were obtained after 30 days due to the presence of Na + and Cl - , which acted as an accelerator to the hydrolyzation process of the MRE. The process then, enhanced the water ingress capability into the matrix to cause the molecular changes. Interestingly, for rheological properties, 30 days of salt water ageing allowed the water molecules to move the MRE matrix molecular chains apart, a process known as plasticization and thus increasing the MR effect. Furthermore, morphological evidence was established to determine the MRE changes during salt water ageing. The research findings should greatly contribute to a better understanding of the effect of salt water on the performance of MRE., (© 2023. The Author(s).)