A Study on Stress Relaxation Behavior of Isotropic Magnetorheological Elastomeric Composite

Experimental study and numerical investigation of stress relaxation behavior of isotropic magnetorheological elastomeric composite (MEC) were carried out in this article. The isotropic MEC was produced from silicone rubber reinforced with micro-sized carbonyl iron particles. The stress relaxation response of the isotropic MEC was investigated at different loading rates, constant strain levels, and under various electromagnetic fields through the single relaxation test with double-lap shear specimens. Research results indicated that the stress relaxation of the isotropic MEC depended slightly on the loading rate, but it was considerably dependent on the constant strain and the electromagnetic field. The shear stress and modulus of the MEC in the relaxation period enhanced with increasing the constant strain and electromagnetic field intensity as well. The stress relaxation of the isotropic MEC was examined numerically using the four-parameter fractional derivative viscoelastic Zener model. The studied fractional derivative viscoelastic model was fitted well to the measured relaxation modulus of the isotropic MEC. The calculated shear stresses of the isotropic MEC with long-term predictions agreed well with the measured ones. Therefore, the investigated fractional derivative viscoelastic model can apply to predict the long-term stress relaxation behavior of the isotropic MEC.