Fabric reinforcements

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Fabric reinforcements

• John Summerscales
• ACMC University of Plymouth

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Outline of this lecture

• Woven fabrics
• Braids
• Knitted fabrics
• Stitched fabrics (non-crimp fabrics)
• Bonded/felted fabrics

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Fabric description

• 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)

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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

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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

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Woven fabrics 2

• plain weave
• 2 orthogonal sets of fibres (?o 1/2)
• high crimp, hence out of plane orientation (??o
  lt 1/2)

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Woven fabrics 3 twill weave

• note the recurring diagonal pattern

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Woven fabrics 4 satin weave

• different fibre orientation on each face
• interlace position is irregular

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Woven fabrics 5 Flow-enhanced

• constrained tow (blue) creates flow space
• mechanical properties decrease

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Triaxial fabrics

• Triaxial (three directions in a single layer)
• usually -60/0/60
• Image from http//hexdome.com/weaving/triaxial/wea
  ving/index.php

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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/in
  fopattern/products/products.php?itemid75langen
  pageproductTree

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Braid

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

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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

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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/st
  ructures/mrw/sylvain.html
• http//cnknitting.en.alibaba.com/product/50139488/
  50653601/multiaxial_fiberglass_fabric/E_Glass_Tria
  xial_Fabric.html

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Bonded/felted fabrics

• chopped strand mat
• Unifilo continuous random swirl fibre mat
• bonding reinforcing scrims (e.g. Crenette)

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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

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Summary

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