In this work, we simulate numerically the filling stage of the injection molding process to predict the orientation of fiber. The suspension simulated consists of rigid glass fibers of 0.5 mm length (aspect ratio of 100) in a polypropylene matrix. An extended Doi model was used to describe the behavior of the highly concentrated fiber in the suspension while a Phan-Thien/Tanner model was used to describe the viscoelastic behavior of the matrix. The suspension was simulated in 2D flow for simple injection moldings (end gate plaque and a center-gated disk) which include a moving front that advances in time.

The numerical technique consists of a standard finite element approximation for the equations of motion and mesh and a discontinuous Galerkin finite element method for the constitutive equations. The typical simulations in the literature to this date have been performed using the Hele-Shaw flow simplification (lubrication approximation), where the front flow is ignored, and the flow and fiber orientation calculations are decoupled. In this work, we present the results of a simulation considering Hele-Shaw flow approximation to compare our results with the values from the literature in which the fiber orientation is postcalculated. We also compare our predictions of the fiber orientation with experimental results. In order to show a more realistic simulation, the preliminary predictions of fiber orientation for a problem considering front flow will be shown.