Scrim (textile technology)

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A scrim is a flat structure that consists of one or more layers of parallel, stretched threads . The threads are usually fixed at the crossing points. The fixation takes place either by material connection or mechanically by friction and / or form fit . The following types of thread layers exist:

  • monoaxial or unidirectional, which are created by fixing a group of parallel threads
  • biaxial, in which two sets of parallel threads are fixed in the direction of two axes
  • multiaxial: several sets of parallel threads are fixed in the direction of different axes.

The thread layers in multi-layer fabrics can all have different orientations, also consist of different thread densities and different thread counts. Compared to woven fabrics , non-woven fabrics have better mechanical properties as reinforcement structures in fiber-plastic composites , since the threads are in a stretched form and therefore there is no additional structural stretch and the orientation of the threads can be specifically defined for the respective application. Because of this elongated shape, a scrim is called non-crimp fabric (NCF) in the English-speaking world and also in international trade.

Manufacturing

Outline sketch of a forfeited multiaxial fabric

For the production of non- woven fabrics, rovings made from man-made fiber filaments (especially made of glass , carbon , aramids ), multifilament yarns made from the same raw materials, but also made from high-strength polyester, and spun yarn made from man-made fibers and natural fibers are used. Rovings, multifilament yarns and staple fiber yarns are also referred to as threads and, accordingly, the scrims produced from them are usually scrims.

The systems for the production of scrims integrate the formation of the scrim structure by means of special thread laying devices as well as the direct connection of the laid threads within a thread layer, if intended, and between the different thread layers, which can reach up to seven layers in multiaxial scrims. The individual layers differ in the thread orientation, the orientation of which is specified with an angle to the production direction (production direction: 0 ° position). There are single-layer, uniaxial fabrics both in the 0 ° and in the 90 ° direction, which are usually directly reinforced with mats or fleeces. There are also two-layer or three-layer (two in the same direction with a differently directed intermediate layer) biaxial scrims in which the threads are usually aligned at 0 ° and 90 ° (but also + 45 ° / -45 °). Multi-layer, multiaxial scrim, with a layer orientation z. B. 90 °, −45 °, 0 °, + 45 ° (four layers), but also other orientation relationships are possible in order to adapt them to the special load conditions in use.

The fixing of the lay threads to one another, particularly in the case of lattice structures, is primarily carried out by special binders applied to at least one thread system or by heat setting when using bicomponent filaments. The mechanical strengthening has prevailed, however, since several thread systems can be connected with it at the same time and free mobility of the lay threads is maintained at the crossing points. The mechanical fixation can be carried out with special embroidery machines, warp knitting machines or sewing machines. The production speed of glass fiber processing multiaxial warp knitting machines is around 6 m / min.

Areas of application

Areas of application in which composite components reinforced with fabrics are used include: a .:

  • Boat and yacht building
  • vehicle construction
  • Rail technology
  • Large container construction
  • Sports equipment
  • Automotive engineering
  • Aircraft construction

Furthermore, clutches come u. a. before in:

Individual evidence

  1. ↑ Walter Loy: Chemical fibers for technical textile products . 2nd, fundamental revised and expanded edition. Deutscher Fachverlag, Frankfurt am Main 2008, ISBN 978-3-86641-197-5 , p. 144.
  2. ↑ Chokri Cherif (Ed.): Textile materials for lightweight construction - Techniques - Process - Materials - Properties . Springer-Verlag, Berlin / Heidelberg 2011, ISBN 978-3-642-17991-4 , p. 293.
  3. ↑ DIN EN 13473-1: 2001-11: Reinforcements - Specification for multiaxial fabrics - Part 1: Designation
  4. ^ Fabia Denninger: Lexicon of technical textiles . Deutscher Fachverlag, Frankfurt am Main 2009, ISBN 978-3-86641-093-0 , p. 150.
  5. ↑ AR Horrocks, SC Annand (Ed.): Handbook of Technical Textiles . Woodhead Publishing, Cambridge 2000, ISBN 1-85573-385-4 , p. 277.
  6. ↑ Burkhard Wulfhorst: Textile Manufacturing Processes - An Introduction . Carl Hanser Verlag, Munich / Vienna 1998, ISBN 3-446-19187-9 , p. 207.
  7. ↑ Walter Loy: Chemical fibers for technical textile products . 2nd, fundamentally revised and expanded edition. Deutscher Fachverlag, Frankfurt am Main 2008, ISBN 978-3-86641-197-5 , p. 144.
  8. ↑ Chokri Cherif (Ed.): Textile materials for lightweight construction - Techniques - Process - Materials - Properties . Springer-Verlag, Berlin / Heidelberg 2011, ISBN 978-3-642-17991-4 , p. 298.