A ONE-WAY COUPLED APPROACH FOR MULTISCALE CHARACTERIZATION OF FILLING OF DUAL-SCALE FIBROUS REINFORCEMENTS CONSIDERING AIR COMPRESSIBILITY AND DISSOLUTION IN LUMPED FASHION

Abstract

The filling characterization of dual-scale fibrous reinforcements is challenging due to the presence of subdomains with dissimilar permeabilities, existence of wicking effects, and combination of air compressibility and dissolution phenomena. These factors cause flow imbalances inside the representative unitary cell (RUC), which lead to void formation and influence the behavior of macroscopic field variables, affecting the parts manufacturing by liquid composite molding (LCM). Here, the filling characterization of woven fabrics used in LCM is done using one-way coupled simulations. Once RUC geometry is characterized by scanning-electron microscopy (SEM), and stereomicroscopy, standard thickness test, and resin viscosity are measured, the multiphase finite volume method-volume of fluid (FVM-VOF) model of ANSYS Fluent is used for the three-dimensional filling of the RUC, incorporating an experimentally calibrated air entrapment parameter (λ) to consider air compressibility and dissolution; then, a lumped function for the coupling term with macroscopic equations is obtained in terms of volume-averaged variables. This function is used in the equivalent Darcy macroscopic model, which is solved using a dual-reciprocity boundary element method (DR-BEM) algorithm. By considering a single value of λ during the simulation, neglecting wicking effects, and normalizing physical variables, unified injection pressure-independent results for the local tows saturation and normalized pressure fields at mesoscopic scale were obtained, as well as for global tows saturation and normalized pressure and fluid front profiles at macroscopic scale, thus simplifying the filling characterization of reinforcements. Numerical results are coherent with unidirectional injection experiments at both scales.