Dry Fabric Forming Analysis Considering the Influence of Tensions on In-plane Shear Behavior

Abstract

In this study, we propose a FE model for dry fabric forming simulation that can express the tension dependent shear behavior in order to predict the wrinkles, one of the major forming defects. Automakers are gradually using more carbon fiber reinforced plastic (CFRP) in mass production cars, because the development of resin transfer molding (RTM) have reduced its cycle time to less than 10 minutes. Finite element analysis (FEA) is essential to the vehicle design process, so numerical simulation of CFRP is strongly desired today. Forming simulation is especially important, because the performance of the final composite part strongly depends on changes in fiber orientation during the preforming. Moreover wrinkle is one of the major defects in preforming. RTM usually involves fabric reinforcement. During forming of fabric, large in-plane shear deformations typically occur. The reason for this is that the shear resistance is very low at the initial stage, because the deformation is governed by yarn contact friction at the cross-sections. Accurately expressing the in-plane shear behavior of fabric is very important for accurate forming simulation. In most simulation models the shear resistance of fabric is assumed to be independent from the tension along the yarn. However, meso-model predictions of the picture frame and bias-extension tests suggest this to be an invalid assumption. In this study, a micromechanical model that introduces the stress component due to the yarn rotational friction is adapted to the dry fabric forming simulation. In other words, this can express the shear behavior that depends on the tensions in the yarns. The results using this micromechanical model are in good agreement with the meso-model results in the various boundary conditions.