Influence of interfacial adhesion on the mechanical response of magneto-rheological elastomers at high strain

This work investigates the interfacial adhesion between the iron fillers and the silicone matrix in magneto-rheological elastomers (MREs) at high strain. Carbonyl iron powder, composed of mechanically soft spherical particles with a median size of 3.5 μm and a volume fraction of 3.5 and 30 %, was mixed in a soft silicone matrix; the compound was then degassed and cured under temperature. The presence of a homogeneous magnetic field of 0.3 T during the curing process allowed the formation of particle chains. Tensile tests of these samples were conducted under scanning electron microscope to simulate and observe interfacial debonding between the two phases. To improve interfacial adhesion, a silane primer was applied to the iron particles, following two different procedures, before the mixing and crosslinking process, thus giving two additional types of samples for each volume fraction. In-situ scanning electron microscope measurements during tensile tests showed that a more elaborated particle–matrix interface was obtained with the primer additive. Furthermore, the structural response of the different types of samples were compared in tensile testing lengthwise to the particle alignment with engineering strains up to 150 %. An enhanced adhesion of the iron fillers to the silicone matrix resulting in a largely increased stiffness at high strain could be observed with the application of the primer. It was observed that the effect of the primer on the debonding of the particles from the silicone matrix has an impact on the macroscopic behavior of the composite only after 80 % deformation in the case of the 30 % volume fraction MRE.