Transcript Training - Plymouth University

Fabric reinforcements
John Summerscales
ACMC University of Plymouth
Outline of this lecture
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Woven fabrics
Braids
Knitted fabrics
Stitched fabrics (non-crimp fabrics)
Bonded/felted fabrics
Fabric description
• warp fibres
picks (shots) run full length of the fabric
• weft fibres (shuttle direction in weaves)
ends run across the fabric
Weft in weave
Warp in weave
Course in knit
Wale in knit
• fabrics are designated by areal weight
normally grams/square metre (gsm)
Balanced fabric
a balanced fabric would have
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equal numbers of
equal weight tows/metre
in both warp and weft
Crimp
crimp ratio = yarn length/cloth length
Woven fabrics 1: weave styles
• Plain
o
high crimp, poor mechanical properties
• Twill
o
intermediate properties
• Satin
low crimp, good mechanical properties
o but beware of orientation of each face
o
• also matt, leno, flow-enhancement …
Woven fabrics 2
• plain weave
• 2 orthogonal sets of fibres (ηo = 1/2)
• high crimp, hence
out of plane orientation (ηo < 1/2)
Woven fabrics 3: twill weave
• Note the recurring diagonal pattern
Woven fabrics 4: satin weave
• different fibre orientation on each face
• interlace position is irregular
Woven fabrics 5: Flow-enhanced
• constrained tow (blue) creates flow space
• mechanical properties decrease
Triaxial fabrics
• Triaxial (three directions in a single layer)
o
usually -60°/0°/+60°
o
Image from http://hexdome.com/weaving/triaxial/weaving/index.php
Three-dimensional fabrics
• 3-D weaving
o
usually multi-layer
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
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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.
Braid
• interlacing three or more threads to produce
a tubular reinforcement
with fibres at ±45° to the principal axis of the tube
• braid calculator
(A&P Technology)
• image from
o
http://www.eurocarbon.com/overbraiding.htm
• Videos:
Braiding the A-pillar for the
Lexus LFA sports car
o Overbraiding at Eurocarbon
(72 second 7 MB MPEG)
o
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
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
Bonded/felted fabrics
• Chopped strand mat
• Unifilo continuous random swirl fibre mat
• Bonding reinforcing scrims (e.g. Crenette)
Pre-impregnated fabrics “prepreg”
• Pre-impregnated fibres/fabrics (lecture C8)
o
pre-pregs
• Resin film infusion (lecture C7)
o
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
o out-life should be recorded
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Summary
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Woven fabrics
Braids
Knitted fabrics
Stitched fabrics (non-crimp fabrics)
Bonded/felted fabrics