Microstructural behavior of magnetorheological elastomer undergoing durability evaluation by stress relaxation

Abstract

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.

Natural Weathering Effects on the Mechanical, Rheological, and Morphological Properties of Magnetorheological Elastomer (MRE) in Tropical Climate

“…Prior to the weather durability test, amorphous molecular structures of the matrix were formed, with initial cross-linkage positions generated after curing with the curing agent. The cross-linking produced by the process has a long and entangled amorphous structure that allowed it to be stretched to its maximum elongation [ 29 ]. As a result of its high elasticity, the SR sample exhibited the greatest elongation in its original state as shown in Figure 4 .…”

The Effect of Microparticles on the Storage Modulus and Durability Behavior of Magnetorheological Elastomer

“…The final stage will be the formation of shear bands as a result of localized strain. The process suffered the amorphous matrix and allows the molecular structure to undergo permanent deformation, a non-reversible change in shape in response to applied forces, at a continuously applied oscillating shear stress and constant strain [ 47 ]. The MRE’s proportionality behavior was slowly reduced as a result of the continuous applied stress at constant strain.…”

“…Figure 7 b, however, demonstrates the distinct feature of a shear band that has undergone stress relaxation. As more slippages at molecular structure level and cross-link losses occur in the MRE, the molecular structure becomes insufficiently reconfigurable, resulting in a permanent deformation (microplasticity or shear band) [ 47 ]. The image was taken from a similar MRE sample of 70 wt% CIP that was tested, and the resulting value is plotted in the graph in Figure 6 .…”

AC magnetorheology of polymer magnetic composites

“…The specific temperature profiles depend on the efficiency of AMF absorption of the CNP 14,15 Rheological studies can be conducted by dynamic mechanical analysis methods under static magnetic fields using commercial instruments, but these accessories do not allow AMF. [16][17][18][19][20][21] In case of commercial rheometers, static magnetic field is generated by an electro-magnetic coil located below the sample, which do not induce induction heating unlike alternating magnetic field. However, engineering to create a magnetic field that oscillates at 400,000 cycles per second (e.g 400 kHz AMF) is very different than that of static magnetic fields.…”