Induced anisotropy by the Mullins effect in filled silicone rubber

This study is concerned with the experimental characterization of anisotropy induced by the Mullins effect in a particle-reinforced silicone rubber. Experimental data concerning the influence of type and direction of initial loading on the subsequent stress softening are quite scarce. In this scope, a set of experimental tests were carried out on a filled silicone rubber. Uniaxial tensile tests and bulge tests were used to precondition the samples, i.e., to induce some primary stress softening. In both cases, subsequent uniaxial tensile tests were conducted on preconditioned specimens. The first set of experiments consists of a uniaxial tension path followed by uniaxial tension along different directions. It appears that the stress softening varies from a maximum in the same direction load to a minimum in the orthogonal direction, with respect to the first tensile load direction. Next, the bulge test is proposed as an original way to yield very different biaxial tensile strain-histories for first loading path. The fact that the biaxiality ratio varies from the pole (uniaxial tension) until the bulge border (planar tension), permits to analyze second tensile load curves in a material that experienced a more complex first load path. These experimental data allow to discuss the most appropriate criteria to describe the strain-induced anisotropy phenomenon.

► Experimental study shows the strongly anisotropy induced by Mullins effect.
► Preconditioning tension in one direction causes weak softening in the perpendicular direction.
► Induced anisotropy by the biaxial pre-stretch is dependent on the biaxiality ratio.
► There is a part of the total strain energy that was not used in the stress softening process.