Phenomenological and Micromechanical Modeling of Anisotropic Effects in Hyperelastic Materials

Hyperelastic materials may exhibit anisotropic effects caused by fiber-reinforcement and filler-particles. In the latter case, anisotropy is induced by directional preconditioning during the production process where a microstructural rearrangement takes place. This behaviour is also known as Mullin's effect that can be treated phenomenologically by elastic damage models. In the framework of the present paper, we discuss a phenomenological approach to model anisotropic behaviour of rubberlike materials. Subsequently, we describe a method to simulate the damage evolution at the microscale where the anisotropy of the material is obtained in a natural way. The damaged material is represented by a soft inclusion embedded in an undamaged matrix material. The growth of the inclusion is formulated in terms of thermodynamic driving forces (also known as material forces) that define the direction of the evolution process.