The effect of extensional viscosity on the core structure of fiber orientation for injection-molded fiber composites

Abstract

Abstract The famous informed isotropic (IISO) viscosity successfully dominates the broader core structure of fiber orientation distributions for injection-molded long fiber composites, due to the flow-fiber coupling effect of stretching deformation. Recently, the GNF-X (Generalized Newtonian Fluid eXtended) constitutive equation of weighted shear/extensional viscosity has been shown to possess the potential to demonstrate the extension-induced corner vortex in the entry flow of a polymer melt. Using GNF-X, three-dimensional injection-molding flow simulations of a center-gated disk are, therefore, performed for verifying the effect of extensional viscosity on the core structure of fiber orientation, namely, the extension-induced fiber orientation. The equivalent of GNF-X and IISO is demonstrated for predicting fiber orientation distribution, while their primary parameter relationship is particularly found herein. It is significant to visualize dramatic patterns of extensional rate occurring in the center-gated disk simulation.