Constitutive modeling of injection-molded short-fiber composites: Characterization and model application

A previously developed constitutive model for short-fiber reinforced thermo- plastics is applied to an injection-molded component with a complex geometry and microstructure. This macro-scale continuum-based model is able to cap- ture the anisotropic viscoelastic-viscoplastic response of the material. In injection-molded short-fiber composites, the anisotropic mechanical properties depend strongly on the fiber orientation distribution, which generally displays a marked variation throughout the product. This makes the material charac- terization and model application challenging. In this article, two characteriza- tion and model application strategies are proposed. These techniques, together with the developed constitutive model provide a strong tool for reliable predic- tion of the mechanical response of an injection molded product, where inputs to the finite element analysis are obtained directly from a numerical simula- tion of the injection molding process. In this article, from the output provided by an injection molding process simulation software such as Moldflow, the dis- tribution of anisotropic elastic and plastic properties throughout the compo- nent is found and the data is imported to the finite element mesh. Mechanical tests are performed on a validation product and results are compared with model predictions from finite element simulations. Through this comparison, the performance of the constitutive model and also proposed procedures for characterization and model application are investigated.