Fabric reinforcements John Summerscales ACMC University of Plymouth

Outline of this lecture 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 fabrics are designated by areal weight normally grams/square metre (gsm) Weft in weave Course in knit Warp in weave Wale in knit

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

Woven fabrics 1: weave styles Plain o high crimp, poor mechanical properties Twill o intermediate properties Satin o low crimp, good mechanical properties o but beware of orientation of each face also matt, leno, flow-enhancement …

Woven fabrics 2 plain weave 2 orthogonal sets of fibres (η o = 1/2) high crimp, hence out of plane orientation (  η o < 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

Three-dimensional fabrics 3-D weaving o usually multi-layer  3D angle interlock (shown)  3D orthogonal (90° binder) o used for preforms Image from 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), Tex Inc

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)braid calculator image from o Videos: o Braiding the A-pillar for the Lexus LFA sports car Braiding the A-pillar for the Lexus LFA sports car o Overbraiding at Eurocarbon (72 second 7 MB MPEG) Overbraiding at Eurocarbon (72 second 7 MB MPEG)

Knitted fabrics knitting is intermeshing of loops of yarn Marvin ( ) 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

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

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 o allow to warm up to avoid condensation o out-life should be recorded

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