Material Designer determines homogenized linear elastic material properties using a micro-mechanical model, either an analytical model or one based on finite elements. On the other hand, it employs a phenomenological model to predict the nonlinear deformation behavior of short fiber reinforced composites. In this approach, the material is considered directly from a macroscopic point of view. A suitable constitutive model is assumed, and its parameters are determined using experimental data.
More specifically, Material Designer models the nonlinear response of short fiber reinforced composites using an anisotropic Hill plasticity model combined with an isotropic hardening law. In doing so, the following assumptions are made:
Viscoelastic effects are neglected.
Strain rate dependence (visco-plasticity) is not considered in the plasticity model– that is, the resulting material model is suitable for simulations in quasi-static conditions.
The yield surface is considered anisotropic, while the hardening law is assumed to be isotropic.
For a detailed experimental characterization of this kind of composite, see for example [Launay, 2011] and [Dillenberger, 2020].