A novel continuum mechanical framework for decoupled material behavior in thickness and in-plane directions

A novel continuum mechanical framework for decoupling the material behavior in in-plane and thickness directions is presented that is motivated by the macroscopic behavior of paper and paperboard. Due to the manufacturing process of these composite materials and the underlying microstructure resulting thereof, the material response is highly anisotropic and can be divided into in-plane and out-of-plane behavior that is independent of each other. This decoupling is mostly incorporated in existing material models by setting the corresponding material parameters to zero which limits the models to an extension to nonlinear problems and is restrictive from a continuum mechanical point of view.