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Volume 15, Issue 3, 2006
ON-SURFACE FIBRE-FREE ZONES AND IRREGULARITY OF PIERCING PATTERN IN STRUCTURALLY STITCHED NCF PREFORMS
Vitaly Koissin1,*, Andreas Ruopp2, Stepan V. Lomov1, Ignaas Verpoest1,
Volker Witzel2, Klaus Drechsler2
1Dept. of Metallurgy and Materials Engineering, Katholieke Universiteit Leuven,
Kasteelpark Arenberg 44, B-3001 Leuven, Belgium
2Institute of Aircraft Design, University of Stuttgart, Pfaffenwaldring 31, D-70569 Stuttgart, Germany
* Author to whom correspondence should be addressed, E-mail: Vitaly.Koysin@mtm.kuleuven.be
Received 6/06; accepted 6/06
ABSTRACT
The paper addresses the surface imperfections (openings in fibrous plies) and irregularity of the piercing pattern in structurally stitched multilayer carbon-fibre preforms. Each layer is a multiaxial multiply non-crimp fabric (NCF) with a non-structural stitching. The term “structural” presumes here that the stitching yarn does not only consolidate the plies (as the non-structural one does) but forms also a through-the-thickness (3D) reinforcement. Four stitching methods are studied: ordinary CNC-sewing, tufting, dual-needle, and curved needle techniques with multifilament yarns: aramide (60 or 120 tex) or glass (204 tex). In total, 14 stitching cases are investigated experimentally. It is observed that a non-negligible variability exists in the meso-level geometry of the reinforcement. The geometrical characterization provides important input data for analysis of the permeability and mechanical properties of the preforms.
KEYWORDS:textile composite, NCF, structural stitching, geometrical characterisation, quality analysis.
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