An FE-based orientation averaging model for elasto-plastic behavior of short fiber composites

A new micro-mechanical model for predicting the non-linear elasto-plastic behavior of short fiber reinforced composites is presented. The model is developed based on a two-step Orientation Averaging method, and is capable of accommodating a wide variety of micro-structural parameters. In the first step, Finite Element Analyses are performed on a unit cell (single fiber surrounded by matrix). Then, the unit cell response is up-scaled by calibrating its response to an elasto-plastic surrogate constitutive model. In a subsequent second homogenization step, a self-consistent interaction scheme is proposed. The predictive capability of the resulting two-step homogenization scheme is then evaluated, next to versions that adopt more traditional averaging schemes (Voigt and Reuss, providing upper and lower bounds, respectively), through comparisons to experiments and direct numerical simulations of realistic Representative Volume Elements. Results show that the model gives fairly good predictions. It is emphasized that the model is capable of accommodating any desired fiber orientation distribution, very large ranges of fiber aspect ratios and fiber volume fractions. Also, the model is computationally very efficient compared to the RVE computational homogenization approach, and thus, it could be conveniently used in applications possessing different fiber orientations at different points of a component.