ABSTRACT
Fiber-reinforced or calendered elastomers are characterized by anisotropy which should be taken into account in the constitutive modeling. This chapter proposes a class of polyconvex anisotropic strain energy functions. A material is said to be orthotropic if it is characterized by symmetry with respect to three mutually orthogonal planes, by reflections from which material properties remain unchanged. The material parameters included in the polyconvex model have been evaluated on the basis of experimental results on calendered rubber sheets. The fitting of the model has been achieved by means of the least squares method where the objective function has been minimized with the aid of a LevenbergMarquardt-type algorithm. Due to the polyconvexity, the proposed model is very suitable for the solution of boundary value problems since the existence of the global minimizer of the total elastic energy of the body is guaranteed. The polyconvexity also ensures ellipticity of constitutive equations.
