A computational investigation of the effective viscosity of short-fiber reinforced thermoplastics by an FFT-based method

Understanding the effective viscosity of fiber-filled polymer melts is essential for predicting the local fiber orientation of injection molded short-fiber reinforced components. To circumvent the intrinsic difficulties of experimentally determining the strongly anisotropic viscosity of such particle-reinforced melts, an FFT-based computational homogenization method for computing the effective quasi-static viscosity of a particle-suspended Newton fluid is introduced, based on a dual formulation. The dependence of the effective viscosity on microstructural parameters, like fiber volume fraction, fiber aspect ratio and fiber orientation are investigated by computational experiments on representative volume elements, and the results are compared to an analytical model for the effective viscosity. Based on the computational findings, a closed-form approximation for the effective viscosity is provided.