Accuracy of the short fibers reinforced composite material plasticity models

Abstract

Composite materials reinforced with short high-strength fibers are used in the aerospace industry, due to their high specific stiffness and strength. The anisotropic nonlinear nature of a short fiber reinforced composites requires the usage of anisotropic plasticity model of the material representative volume mechanical characteristics to predict the stress-strain state of the molded products. In this work, was made a comparison of three models of binder hardening - power, exponential and linear-exponential laws. The models were built in the Digimat MF system. The models describe tension of ISO 527-2 samples of 50% short glass-fiber reinforced polyamide PA6, cut out from plate at angles of 0, 45 and 90 to the molding direction. The models parameters were identified by reverse engineering in the Digimat MX. The paper gives estimates of the accuracy of approximating the plasticity curve in each tension direction by the investigated models. The influence of the Mori Tanaka and the double inclusion homogenization schemes is investigated. It is shown that the exponential hardening law makes the best tension curve approximation with mean relative error less than 3.8% and maximum relative error less than 9.7%.