Micromechanical validation of a mesomodel for plasticity in composites

In this paper, the performance of a recent homogenized orthotropic plasticity model for fiber reinforced composites (Vogler et al. (2013)) is investigated by comparing the model response against a micromechanical model. It is assumed that the micromechanical model which contains a recent plasticity model for polymers (Melro et al. (2013a,b)) offers a realistic representation of the plastic deformation of composite materials. Under that assumption, the performance of the homogenized model can be assessed based on the question how well it reproduces micromechanical results. Improved consistent tangent formulations for both plasticity models are presented and a study into the representative volume element size for elasto-plastic micromechanical analysis is performed. Micromechanical simulations of basic load cases are used to generate input for the homogenized model. Next, the response of the two models is compared for a range of different load cases. The loss of accuracy due to necessary simplifications in the homogenized model is quantified in the comparison. These simplifications in the mesomodel include ignoring the stress in fiber direction, disregarding the influence stress orientation under combined longitudinal shear and transverse loading, and the use of a single constant plastic Poisson ratio.