Multiscale CFD Simulation of Impregnation Die for Unidirectional Composites Production: Velocity Coupling Strategy Between Meso- and Macro- Scales

The permeability of a porous bundle of carbon fibers and impregnation rate are important factors of impregnation process of uni-directional carbon fiber composites (UD-CFC). Although the permeability of a porous medium is theoretically determined by Darcy’s law , there is a lack of knowledge for multiscale interactions of a moving porous medium system in the UD-CFC impregnation process. In order to analyze the effects of the microscale structure and moving speed of carbon fiber in the presence of initial volatile material and polymer matrix on permeability and impregnation rate, a multiscale computational fluid dynamics (CFD) model including a microscopic 3D CFD model of a representative volume of tow segment with the real dimension of carbon fibers, and a macroscopic 3D CFD model for the whole dimension of the impregnation die was proposed. A moving frame reference approach for the tow domain was used in the macroscopic CFD model. The anisotropic and homogeneous permeability of the porous tow was calculated from the microscopic CFD model. The penetration velocity at the macroscopic CFD model was chosen as a convergence criterion for the multiscale iterations. Finally, a converged solution for permeability and impregnation rate of the porous CF bundle was obtained.