Large Deformation of Particle-Filled Rubber Composites

Soft materials such as rubber may be stiffened by mixing with high modulus particles. In order to investigate their large behaviors at large deformation, particle-filled silicone rubber (RTV) specimens are fabricated. Although there have been numerous experiments for composites, a limited number of tests exists for finite deformation investigation of composites filled with uniformly shaped particles. In the tests, two types of particles are used. One is uniform glass beads with about 55 mu m diameter and the other is spherical zirconia powder with diameters ranging from 30 to 80 mu m. The former composites showed initial stiffening but the effects were limited as debonding of particles from matrix rubber occurs at large stresses. The latter composites showed better bonding as their surfaces are rough. Specimens are loaded multiple times in tension and compression. Their nonlinear behaviors as well as the Mullins effects are analyzed. The observed experimental results were compared with 3D finite element calculations as well as various nonlinear constitutive models and the rule of mixture.