Magnetoactive elastomer composites

Abstract

This paper deals with the development of magnetoactive elastomers and the exploration of some of their potential applications. In the course of material development, samples of particle-filled silicone rubber were produced and their mechanical and magnetic properties were experimentally determined. The test specimens consisted of pure and filled silicone with randomly dispersed as well as aligned magnetizable particle chains. To align the embedded particles in the elastomer, cross-linking of the resin took place in a magnetic field. Composite elastomer samples with different types of micron-size particles and various volume fractions were tested. Through alignment of the embedded particles, relative to pure silicone, the tensile strength increased by 80%, the tensile modulus by 200%, and the compression modulus by more than 300%. The maximum tensile strain of filled samples was generally reduced; however, samples with longitudinally aligned particles retained a relatively high strain capability as in the pure silicone rubber. Furthermore, to determine the active response of the composite, magnetic tests and coupled mechanical-magnetic experiments were performed. The magnetoactive elastomer composites produced and tested in this work demonstrated certain actuator force properties. The equivalent magnetic force calculated on the basis of these experiments and the magneto-solid mechanics theory showed the dependence of the magnetic force on the distribution of the particles in the elastomer. The elasto-magnetic behavior of beam samples was investigated by exposing the filled elastomer to the action of a permanent magnet at various gap distances, which led to the determination of a so-called magnetic bending stiffness. Moreover, through these experiments the influence of the particle alignment on the critical gap distance of the elasto-magnetic instability of composite elastomer was quantitatively estimated. The compression tests on cylindrical samples in the absence and the presence of a magnetic field showed that the magnetic field would increase the stiffness of the material. These experiments lead to useful hints regarding the use of such elastomer composites as tunable force structural elements.