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Textile Reinforcements for Composites Lecture

Detailed overview of woven, braided, knitted, stitched, and bonded fabrics used for composites reinforcement by John Summerscales from the University of Plymouth. Includes fabric types, weave styles, fabric properties, and 3D fabrics.

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Textile Reinforcements for Composites Lecture

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  1. Fabric reinforcements John Summerscales University of Plymouth

  2. Outline of this lecture • woven fabrics • braids • knitted fabrics • stitched fabrics (non-crimp fabrics) • bonded/felted fabrics

  3. Fabric description Weft in weave Course in knit Warp in weave Wale in knit • warp fibres picks (shots) run full length of the fabric • weft fibres (shuttle direction in weaves) ends run across the fabric • fabrics are designated by areal weight normally grams/square metre (gsm)

  4. Balanced fabric • a balanced fabric would have • equal numbers of equal weight tows/metre in both warp and weft • Crimp • crimp ratio = yarn length/cloth length

  5. Woven fabrics 1: weave styles • plain • high crimp, poor mechanical properties • twill • intermediate properties • satin • low crimp, good mechanical properties • but beware of orientation of each face • also matt, leno, flow-enhancement …

  6. Woven fabrics 2 • plain weave • 2 orthogonal sets of fibres (ηo = 1/2) • high crimp, hence out of plane orientation (ηo < 1/2)

  7. Woven fabrics 3: twill weave • note the recurring diagonal pattern

  8. Woven fabrics 4: satin weave • different fibre orientation on each face • interlace position is irregular

  9. Woven fabrics 5: Flow-enhanced • constrained tow (blue) creates flow space • mechanical properties decrease

  10. Triaxial fabrics • Triaxial (three directions in a single layer) • usually -60°/0°/+60° • Image from http://hexdome.com/weaving/triaxial/weaving/index.php

  11. Three-dimensional fabrics • 3-D weaving • usually multi-layer • 3D angle interlock (shown) • 3D orthogonal (90° binder) • used for preforms Image from http://www.designscopecompany.com/en/infopattern/products/products.php?itemid=75&lang=en&page=productTree Layer to layer interlock weave Angle interlock weave Orthogonal non-crimp interlock weave Images from AE Bogdanovich and MH Mohamed (3Tex Inc), SAMPE Journal, 2009, 45(6), 8-28.

  12. Braid • interlacing three or more threads to producea tubular reinforcement with fibres at ±45° to the principal axis of the tube • braid calculator (A&P Technology) • image from • eurocarbon.com/overbraiding.htm(NLA) • Videos: • Braiding the A-pillar for theLexus LFA sports car • Overbraiding at Eurocarbon(72 second 7 MB MPEG)

  13. Knitted fabrics • knitting is intermeshing of loops of yarn • Marvin (1961-69) knitted rocket nose cones • can form complex shapes or create a matrix for aligned fibres: • WIWK = weft-insertion warp knit or = warp-insertion weft knit • image from http://en.wikipedia.org/wiki/Knitting

  14. Stitched (non-crimp) fabrics detail of the stitch photo of real fabric cross-section of laminate • unidirectional layers stitched together • Beware!stitch fibre may be incompatible with the matrix • images from http://www.aer.bris.ac.uk/research/structures/mrw/sylvain.html http://cnknitting.en.alibaba.com/product/50139488/50653601/multiaxial_fiberglass_fabric/E_Glass_Triaxial_Fabric.html

  15. Bonded/felted fabrics • chopped strand mat • Unifilo continuous random swirl fibre mat • bonding reinforcing scrims (e.g. Crenette)

  16. Pre-impregnated fabrics “prepreg” • pre-impregnated fibres/fabrics (lecture C8) • pre-pregs • resin film infusion (lecture C7) • thick sheet of B-stage • both systems have a limited shelf-life • usually stored in freezer to retard cure • allow to warm up to avoid condensation • out-life should be recorded

  17. Summary • woven fabrics • braids • knitted fabrics • stitched fabrics (non-crimp fabrics) • bonded/felted fabrics

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