Constitutive modelling of calendering induced anisotropy in rubber sheets

In experiments, calendered rubber sheets reveal an anisotropy and in particular transverse isotropy with respect to the calendering direction ( Diani et al. 2002 ). In the present contribution this anisotropy is taken into account by means of a generalized hyperelastic orthotropic model ( Itskov 2001 ). The model is based on the St.Venant-Kirchhoff stored energy function formulated in terms of the generalized strain measures. These strain measures are approximated by tensor power series with the arbitrary number of terms and associated material constants. With the aid of the least-squares method these constants are evaluated in order to fit the model to the experimental data mentioned above. A good agreement in the wide range of deformations is observable.