Original Article Journal of Intelligent Material Systems and Structures 1–15 Ó The Author(s) 2018 Article reuse guidelines: sagepub.com/journals-permissions DOI: 10.1177/1045389X18808393 journals.sagepub.com/home/jim Performance of natural rubber and silicone-based magnetorheological elastomers under large-strain combined axial and shear loading Siddaiah Yarra 1 , Faramarz Gordaninejad 2 , Majid Behrooz 2 and Gokhan Pekcan 1 Abstract This study presents an experimental investigation on large-strain behavior of natural rubber– and silicone-based magne- torheological elastomers within a larger scope of structural vibration mitigation due to wind, traffic and seismic events. Magnetorheological elastomer samples with different weight percentages of iron particles, additives, and elastomer matrix were fabricated. The microstructures of specimens were examined, and their mechanical properties were investi- gated by a unique electromagnetic double-lap shear experimental setup capable of applying simultaneous compression and shear loads. The experimental results demonstrated that the isotropic natural rubber–based magnetorheological elastomers exhibit about 30% magnetorheological effect under large strains, while they achieve a higher magnetorheolo- gical effect under the combined axial and shear loading. The magnetorheological effect was 92% and 33% for 10% and 100% shear strains when 100 psi axial stress was applied. A natural rubber–based magnetorheological elastomer was fur- ther investigated applying dynamic cyclic load with and without compression load for different strains, frequencies, and magnetic field intensities. It was observed that for higher frequency, magnetorheological effect was reduced. Magnetorheological effects were 73% and 29% for0.1 and 10 Hz frequencies, respectively, under 100 psi axial stress at 150% shear strain. The result of this study suggests that isotropic natural rubber–based magnetorheological elastomers may be suitable for high-demand-force applications, and in particular, in civil structures. Keywords Magnetorheological elastomers, natural rubber, carbon black, shear and compression loading Introduction Conventional (passive) elastomers, such as natural rub- ber, have been utilized in structures, vehicles, and other machineries to mitigate shock and vibration. Passive elastomeric layers have limitations in accomo- dating a wide range of operating conditions. Magnetorheological elastomers (MREs) are a class of materials whose monotonic (shear modulus) and dynamic (storage and loss moduli) properties can be tuned by an external magnetic field. For the fabrication of MREs, magnetically permeable particles are mixed with an elastomeric matrix. When the mixture is cured under a magnetic field, iron particles form chains. On the other hand, when the mixture is cured without a magnetic field, iron particles randomly scatter in elasto- mer and result in an isotropic MRE. Polyurethane-based anisotropic MRE showed 20% better magnetorheologi- cal (MR) effect than anisotropic natural rubber MRE (Shen et al., 2004). Gong et al. (2005) investigated the relation between microstructure and mechanical proper- ties of isotropic MREs and concluded that the isotropic MRE with 70%wt. iron particle showed 51% MR effect. Chen et al. (2007) reported 133% MR effect for the 80%wt. anisotropic natural rubber MRE. Lokander and Stenberg (2003) demonstrated that natural rubber–based isotropic MR material with irre- gularly shaped iron particles has a better MR effect than with carbonyl iron. However, MR effect was 1 Department of Civil and Environmental Engineering, University of Nevada, Reno, NV, USA 2 Department of Mechanical Engineering, University of Nevada, Reno, NV, USA Corresponding author: Faramarz Gordaninejad, Department of Mechanical Engineering, University of Nevada, Reno, NV 89557, USA. Email: faramarz@unr.edu