Stretch induced anisotropy and fracture toughness: An experimental study on a silica- filled NBR compound

Anisotropic pre-stretching of a filled rubber compound is responsible for the anisotropic behaviour of the stretched material, which is commonly evidenced by evaluating only the tensile response of the prestretched material. In this work, an evaluation of the effects of stretch-induced anisotropy on the fracture behaviour of the material was also carried out. Preliminary pre-stretching of silica-filled SBR-based compounds was performed by deforming the material under uniaxial or equibiaxial tensile conditions or under pure shear deformation conditions, up to different strain levels. The tensile and fracture behaviour of the softened material was evaluated along two perpendicular directions and correlated with both the principal strains applied and the biaxiality index defined to characterize the anisotropy of preliminary stretching