Investigation of the mechanical properties of anisotropic elastomer composites reinforced with carbon black particles of different brands showed a significant difference in the behavior of samples for both strength characteristics and degree of softening. Cross-shaped samples were subjected to uniaxial tension in two orthogonal directions on the Zwick biaxial testing machine. Anisotropy of the mechanical properties is strongly marked for samples, which have larger hysteresis loop during the first loading-unloading cycle.Numerical simulation of the loaded segment of small volume from filled elastomer showed that values of the total strain energy accumulated during deformation along different axes are substantially different from each other. This difference was obtained due to the elastoplastic behavior of the interface layer, where the accumulation of residual strain occurs differently in different directions of loading.