Numerical Simulation Of Dual-Scale Flow In 3D Interlock Fabrics With Consideration Of Capillary Effects
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In the field of composite materials manufacturing, the multi-scale structure of reinforcements used (3D interlock fabrics) involves dual-scale flows of a liquid polymer resin. A detailed understanding of these flows occuring both between and within homogenous equivalent porous yarns (bundle of fibres) is required to predict potential impregnation defects. Mesoscopic unit cells of the fabric are described by both yarn morphology and intra-yarn permeability field. This dual-scale nature has a significant impact on saturated fluid flows, influencing the fabric effective permeability. Furthermore, this effect is even more meaningful on unsaturated flows due to capillary phenomena within yarns. Capillary forces are modelled by a capillary pressure considered as a pressure discontinuity applied on the fluid front in fibrous media. Our aim is to develop a robust numerical framework to simulate fibrous media impregnation at mesoscopic scale. The fluid flow is modelled by Darcy equation within the porous yarns and by Stokes equation between the yarns. A monolithic approach is used to solve the Stokes-Darcy coupled FE problem with a mixed velocity-pressure formulation stabilised by a VMS method. A pressure enriched space is introduced at the fluid interface represented by a level set function in order to capture the pressure discontinuity in Darcy domains. Both convergence and implementation are first validated and then a comparison with experimental measurements shows a good agreement with numerical simulations.
