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Fabric reinforcements

Fabric reinforcements. John Summerscales University of Plymouth. Outline of this lecture. woven fabrics braids knitted fabrics stitched fabrics (non-crimp fabrics) bonded/felted fabrics. Fabric description. Weft in weave Course in knit. Warp in weave Wale in knit.

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Fabric reinforcements

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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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