Numerical study on air retention in fibrous media with dual-scale structure by a PF-LB model

Abstract

Defects often occur due to air retention and poor infiltration in resin filling process in resin transfer molding (RTM). Investigating the characteristics of resin filling and the mechanism of air retention for dual-scale variables in a fiber preform is crucial for reducing the defects in composites. A phase-field lattice Boltzmann (PF-LB) model for immiscible multiphase flows with large density and viscosity ratios is built to simulate resin filling process in RTM. Two cases are used to verify the validity and feasibility of the PF-LB model. Basing on the improved PF-LB model, we simulate two-phase flow within dual-scale fiber bundles and predict the air retention rate. The numerical results reveal that the geometry variables perpendicular to the flow direction determine air retention process. The micro-scale variables have greater impact on the resin filling process than the meso-scale variables. A new empirical relationship of air retention rate related two-scale structural variables and modified capillary number is proposed.