Directional model for anisotropic hyperelastic rubber-like materials

A material direction-dependent constitutive model has been formulated for large deformation of anisotropic rubber-like materials. Anisotropic behavior has been observed in calendered plates of filled elastomers. Strain energy density functions characterizing rubber-like material behavior are usually dependent on the principal stretch ratios and are unable to take into account anisotropy. The proposed strain energy density depends on material directions and accounts for anisotropy. Model material directions have simply been chosen using existing macromolecular model chains geometry. The material strain energy density is given as the sum, over all material directions, of the elementary directional strain energy density. This elementary strain energy is determined by analogy with chain entropy of macromolecular models using the Langevin statistics. To evaluate the effectiveness of the proposed model, it is compared to uniaxial tension experimental data of anisotropic hyperelastic rubber-like materials.