Conference Paper

Permeability Prediction Using Porous Yarns in a Dual-Scale Simulation with Openfoam

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Abstract

Experimental permeability test benches are state of the art. The main reason for the use of these test benches is the easy flow monitoring, the reproducibility and the analogy to simple geometries. Such test benches can only be used to approximate LCM processes used in real production cycles. The authors assume that there are three main areas where discrepancies can occur between experimental test and reality: 1) Experimental set-up 2) Complexity & Effort 3) Applicability for real production To avoid such discrepancies a near-net-shape virtual permeability determination can be used. In this paper a simulation approach with porous yarns will be presented to predict dual-scale flow permeabilities in 3D textile preforms. The transfer of permeability values to commercial FEM-filling tools will be shown. First of all, a triaxial braided 12K RVE model, the fibre architecture and the import of porous yarns to the OpenFOAM CFD software tool will be presented. In a second stage, microscopic simulations on filament level for yarn permeabilities will be discussed and implemented into the overall 3D dual scale flow simulation. In the next stage the permeability prediction will be explained using the CFD flow conditions and a modified Darcy’s law for RVE level and a near-net-shape braided tube. Challenges will be illustrated and possible solutions will be discussed. In a final step the permeability prediction of the different simulation approaches will be compared.

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... Most of them are based on the assumption of parallel filaments with circular crosssections. Structural simulations and steady-state flow simulations with such idealised RVEs show reasonable results [1] [3]. However, yarns with higher yarn counts show a strong deviation from circular cross-sections and mean diameter (cf. ...
Conference Paper
Full-text available
Introduction Microscopic flow and structural simulations are used for virtual material characterisation. Several well described methods to generate representative volume elements (RVE) of yarns are already published [1] [2]. Most of them are based on the assumption of parallel filaments with circular cross-sections. Structural simulations and steady-state flow simulations with such idealised RVEs show reasonable results [1] [3]. However, yarns with higher yarn counts show a strong deviation from circular cross-sections and mean diameter (cf. fig. 1). To reach a RVE, which is as realistic as possible, different new aspects such as non-circular cross sections and bundles within the RVE are taken into account. The aim of the described approach is, to get a RVE that enables the virtual characterisation for filling and forming simulations as accurate as possible.
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