XCT-scan assisted flow path analysis and permeability prediction of a 3D woven fabric

Compaction response and resin flow through a fabric are key characterization parameters in Liquid Composite Molding (LCM) processes. In this study, we present a detailed flow path analysis of a complex 3D woven angle interlock fabric using an in-situ X-ray micro computed tomography (XCT) experimental set-up. The set-up is used to obtain the reinforcement compaction response and three principle permeability values at different thicknesses in a single experiment. The compaction provides real-time features of inter-tow gaps, as well as elongation/spreading of weft and warp tows associated with a through-thickness deformation of the binder yarn. The reduction of the pore network during compaction is analyzed through pore size distribution using a granulometry and percolation path analysis. The resin flow path and reinforcement permeability in principle directions are predicted through vigorous digital flow simulations using several computational unit cells extracted from the reconstructed 3D models from XCT scans. The resin flow paths and principle permeability values show a very strong dependence on the solid volume fraction of the scanned images. A relationship between the solid volume fraction and permeability is developed using a modified Kozeny-Carman relation. The predicted permeability values were found to be in good agreement with traditional benchmark experimental data, highlighting the utility of this novel technique.