A Numerical Analysis of Resin Flow in Woven Fabrics: Effect of Local Tow Curvature on Dual-Scale Permeability

Abstract

Permeability is a crucial flow parameter in liquid composite moulding (LCM), which is required to predict fibre impregnation, void formation and resin back flow. This work investigates the dual-scale (micro- and meso-) nature of permeability during resin infusion into woven fabric by incorporating the intra tow flow where the degree of local tow curvature (tow/yarn undulation) is taken into account. The mesoscopic permeability of a dual-scale porous media in a unit cell is estimated using Darcy’s law, where the Gebart analytical model is applied for the intra tow flow in longitudinal and transverse directions with respect to distinct fibre packing arrangements. The results suggest that for a low fibre volume fraction (≤42%), the degree of local curvature at the mesoscale can be neglected. However, for a high fibre volume fraction (>42%) and a higher fibre bundle curvature, the proposed model should be adopted, since the resin flow is affected by a mesoscopic tow curvature that could result in around 14% error in predicting permeability. It is shown that the permeability results of the current study are in good agreement with and in the range of the retrieved available experimental data from the literature.

Numerical Investigation of Multi-scale Characteristics of Single and Multi-layered Woven Structures

“…A porous model is one of these offered tools, during which an additional source term is added to the N-S equations. This allows modelling inter-tow flow together with intra-tow flow [19][20][21]. The conservation of momentum and mass (continuity) equations for laminar viscous flows in an inertial frame of reference (a stationary frame) is presented below:…”

“…This has motivated researchers to investigate permeability and porosity phenomena in single-or dual-scale fibrous media. A considerable amount of contributions have been made to this field in terms of experiments [8][9][10][11], analytical models [12][13][14][15][16], and numerical simulations [17][18][19][20][21]. In terms of numerical approaches, there has been numerous work using finite element, finite volume, finite difference, and Lattice Boltzmann methods that are sufficient in modelling creeping/viscous flow problem in fibrous porous media [17][18][19][20][21].…”

Review on Manufacture of Military Composite Helmet

“…The pores, fibre orientation and fibre volume fraction distribution inside these fabric types present various interconnections and patterns, giving different fluid flow resistance. Besides, the crimps (curvature) level determines the suitability for ballistic application, simultaneously influencing the flow pattern [34] in later resin filling process or response to compression force. These structural heterogeneities lead to scatter in permeability and composite thickness, having further impact in process-induced defects.…”

“…Like that in the thermo-mechanical forming, the frictional interaction between yarns and plies, or preforms and tools, in LCM will take place subjecting to vacuum before or during resin filling, having a significant effect on wrinkles formation [97]. Nesting phenomenon and geometrical variants [34] are induced by compaction in thickness direction. The compaction from vacuum will also get the pore pattern inside the structure changed and the permeability of fabric vary that will add uncertainty to the part quality.…”

“…it presented non-linear when shear angles over 20° [100]. More fluid flowing models have been reviewed in [34].…”