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Permeability characterization of porouspreform during VARTM using fractals

Adhikari, D and Gururaja, S (2019) Permeability characterization of porouspreform during VARTM using fractals. In: 18th European Conference on Composite Materials, ECCM 2018; Megaron Athens International Conference, 24-28th June 2018, Centre (MAICC)Athens; Greece.

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Abstract

Accurate characterization of permeability of the complex architecture of porous preform is the first step towards efficient and cost-effective resin impregnation to yield composite parts via vacuum assisted resin transfer molding (VARTM). Determination of preform permeability in different directions is inherently dependent on the available pore spaces in the complex labyrinth of the fabric layup. A major challenge is to understand the pattern of disordered complex microstructure and a quantitative description of permeability as a function of local porosities. Depending on the fiber alignment, several models have been developed to determine permeability as a function of fiber volume fraction by means of flow thorough ordered compacted parallel and perpendicular channels. It was observed that in most cases, experimentally determined permeability fitted well with the classical permeability porosity relation of Kozeny-Carman (KC) model with an empirical Kozeny constant as a fitting estimate. KC model shows that as the fiber volume fraction decreases the permeability increases; however, results indicate that in some cases, this behavior is not exhibited. Detailed permeability experiments conducted on carbon fiber preform YC200 (Fibertech Co. Ltd.) show that as the fiber volume fraction increases, the permeability along the fiber direction increases; the converse was found to occur for permeability experiments conducted on the fabric in the transverse direction. Once the fiber layups are stacked together, diameter of micro pores and capillary channels do not behave like perfectly aligned parallel micro channels. There is considerable disorder in the preform microstructure in terms of different capillary diameters, length of the tortuous capillaries between tows, spacing between individual filaments within a single tow, and the spacing between stitching threads of the fabric, etc. In the present study, two separate unit cell models have been developed with and without a combination of pore area fractal dimension and tortuosity. Predicted results a good agreement with the experimentally determined permeability in both the longitudinal and transverse directions.

Item Type: Conference Paper
Publication: ECCM 2018 - 18th European Conference on Composite Materials
Publisher: Applied Mechanics Laboratory
Additional Information: cited By 0; Conference of 18th European Conference on Composite Materials, ECCM 2018 ; Conference Date: 24 June 2018 Through 28 June 2018; Conference Code:155810
Keywords: Compaction PressureFractalsPermeabilityTortuosity
Department/Centre: Division of Mechanical Sciences > Aerospace Engineering(Formerly Aeronautical Engineering)
Date Deposited: 23 Jan 2020 09:24
Last Modified: 23 Jan 2020 09:24
URI: http://eprints.iisc.ac.in/id/eprint/64383

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