The automobile industry has strengthened requirements for lighter components with the aim of improving fuel efficiency and reducing environmental problems. These requirements have been addressed in a variety of studies. For example, vehicle components traditionally composed of metallic materials are being replaced by polymer composites like fiber reinforced plastics to fulfill the weight requirements. Polymer composites consist of a matrix such as thermoplastic or thermosetting polymer, and fiber inclusions made of such as glass or carbon. Glass fiber reinforced plastic composites, which are produced using the injection molding process, are widely used in the internal and external components of vehicle structures, due to their lightweight structure, high mechanical strength, excellent electrical insulation, easy molding and rapid manufacturing processes. Finite element method (FEM) is a numerical method for analyzing and predicting the mechanical behavior of materials realistically in various engineering fields. However, the approach using numerical analysis on glass fiber reinforced plastic composites makes it difficult to define material characteristics that are anisotropic with respect to fiber orientation.
In this study, Digimat, a multi-scale material modeling program based on mean-field homogenization methods to describe the mechanical properties of glass fiber reinforced plastic composites, was used. The fiber orientation tensors calculated from the injection analysis using Moldflow were transferred to structural FE models with the mapping process of Digimat-MAP. The coupled analysis, which reflected anisotropic behavior according to fiber orientation, with LS-DYNA and Digimat was able to more effectively verify and predict the tensile and fatigue properties of fiber reinforced polymer composites. Fatigue analysis took into account influence factors such as fiber orientation, relative stress gradient and mean stress that had an effect on the fatigue property of glass fiber reinforced plastic composites. Fatigue life was analyzed according to stress ratio and type of specimen using FEMFAT program consisting of material models applicable to these factors. The fatigue analysis of anisotropic linear material model used Neuber''s rule to study in low cycle fatigue where non-linearity occurs locally and was compared with the fatigue analysis of anisotropic and isotropic nonlinear material models. Consequently, an effective method using finite element analysis applicable to various components including glass fiber reinforced plastic composites was presented.