Textile Structures for
Composites
Objectives
 After studying this chapter, you should be able
to:
Describe major textile preform structures used in
composites including their advantages and
disadvantages, and how they are made.
Calculate theoretical volume fractions for
selected types of preforms.
Select right type of preform for a particular end
use.
Explain qualitatively the effect of fiber orientation
and fiber volume fraction on composite
mechanical properties.
Textile Structures for Composites
Reading assignment:
Text book, Chapter 3;
Dow, N.F. and Tranfield, G., Preliminary investigation of
feasibility of weaving triaxial fabrics (Doweave), Textile
Research Journal, 40, 986-998 (November, 1970).
Mohamed, M., Three dimensional textiles, American
Scientist, 78, 530-541(November-December, 1990).
Popper, P., Braiding, International Encyclopedia of
Composites, Vol. 1, Edited by Lee, S.M., VCH Publishers,
New York, 130-147 (1990).
Jones, F.R., Handbook of Polymer-Fiber Composites,
Section 1.12. Knitted reinforcements
How Nonwovens Are Made
Textile Structures for Composites
Unidirectional
Laminae (ply)
Laminates: a stack of laminae
Textile Structures for Composites
Two dimensional (Laminates)
 Nonwoven:
• short fibers and continuous fibers, plates,
• particulates
 Woven
•
•
•
•
Biaxial
Triaxial
Knitted
Braided
Textile Structures for Composites
Three dimensional
 Nonwoven
 Woven
•
•
•
•
Orthogonal
Multi-directional
Knitted
Braided
 Combination
Structure property relations of composites
System
Picture
Property
Strength(MPa)
Modulus(GPa)
Strain(%)
isotropic
64 - 83
2.1
4-6
isotropic
62 - 72
10.3
2 - 2.5
Short fibers
planar
isotropic
38
9.6
0.4
Short fibers
planar
isotropic
270
32
0.6 - 1.0
Conti.
fibers
planar
isotropic
28
12.4
0.4
Conti.
fibers
planar
isotropic
890
43.4
2.0
Resin
Bead filled
Textile Structures for Composites
Unidirectional and 2-D preforms
Laminates
From lamina to laminate
 Lamina: unidirectional, woven, knitted, braided or
nonwoven
 Laminate
Factors effecting laminate properties





Fiber and matrix properties
Interface properties
Fiber volume fraction
Fiber/lamina Orientation
Fiber length
Orientation of short fiber composites
 Fiber orientation determines the mechanical
properties
 Important for non-woven and sheet molding
compound
 Orientation characterized by normalized
histograms (in plane)
Image analysis of a photograph
Directions divided into number of “bins”
The radius of each bin proportional to fraction of
fibers oriented in that direction
Nonwoven preforms

Nonwoven web-forming processes:




Wet laying
Dry laying
Other Methods
Nonwoven bonding methods:
Latex bonding (2D)





Saturation bonding
Gravure printing
Screen printing
Spray bonding
Foam bonding
Nonwoven preforms
Nonwoven bonding methods
 Mechanical bonding (3D)
Needle punching
 Spunlacing (water jets)
 Stitch bonding
 Knitting through

 Thermal
bonding (2D)
Through-air bonding
 Calender bonding

Three dimensional textiles
3D woven fabrics
Structure
Weaving processes
Performance
Shear strength: 300%
Interlaminar tensile strength: 200%
Flexure strength: 65% higher
Failure mode: micro-buckling of fibers
Three dimensional textiles
Knitted and braided forms
Weft knitting
Warp knitting
with weft insertion
 multiaxial warp knitting

3D braiding
Braiding
 Braiding process and
terminology
Braiding yarns
Axial yarns
Core yarns
Mandrel
Carrier
Horn gears
Convergence zone
Braiding angle θ
Pick
Width or diameter
Braiding
 Machines
 Circular 144 carriers, <400 ppm
 Grouped carrier <1200 ppm
 Jacquard: enables connected sets of yarns to braid
different patterns
 Special pattern
 Solid rope: all carriers move around a horn gear in
one direction
 Packing braider <230 ppm, solid square cross-section
 3D: >2000 carriers circular
>12000 carriers rectangular
3D-Braiding
4-Step Braiding
• Step 1
 Original
• Step 2
• Step 3
• Step 4
Braiding
Unique features:
 Fabric can be formed over a complex
shaped mandrel
 Yarns feed on demand
 Yarn and elements insertion possible
 Possible to change the sequence of
interlacing
 Improved fracture toughness
 Decreased sensitivity to holes
Braiding
Limitations




Move entire supply of braiding yarns
Machine >> product
Moderate aspect ratio only
Fiber orientation angle varies arbitrarily
Comparison of textile structures for composites
Fiber orientation
Structural integrity
interlaminar connection
broken ends,
resin pocket,
formation of holes, inclusion of elements etc.
Comparison of textile structures for composites
Fiber volume fraction
Productivity
formation of the fabric,
easiness to handle,
formation of composites
Comparison among 1-D, 2-D and 3-D
1D: Unidirectional laminates
Advantages:
 Highest productivity for preforms
 Highest strength and modulus in fiber oriented
direction
 Highest fiber volume fraction.
Disadvantages:
 Poor strength and modulus in off-axis directions
 Poor compression properties
 Delamination possible
Comparison among 1-D, 2-D and 3-D
 2D: Woven fabrics, Nonwovens, laminates
with differently oriented laminas
Advantages:
 High productivity.
 Better properties (tensile strength and modulus)
in both X and Y directions or even diagonally.
Disadvantages:
 Poor interlaminar properties and properties in
thickness directions (tensile, shear).
 Delamination possible.
 Lower fiber volume fraction than 1D.
Comparison among 1-D, 2-D and 3-D
3-D: (Woven, Nonwoven)
Advantages:
 High strength and modulus in all three directions
 No delamination
 Good structural integrity (not many broken fiber ends)
Disadvantages:
 Low productivity
 Low fiber volume fraction
Comparison: Woven versus nonwoven
Woven
Nonwoven
Anisotropic
Planar Isotropic
High strength and modulus in fiber Low strength and modulus in all
oriented directions
directions
Low strength in off-axis directions
Strength is the same in all
directions
Relatively low productivity
High productivity
High fiber volume fraction
Low fiber volume fraction
Comparison of Woven Fabrics
Properties
Woven
Knitted
Braided
Fiber orientation
Orthogonal
Varies
Varies
Dimensional
stability
Good
Poor
Poor
Structural
versatility
Poor
Moderate
Good
Productivity
High for 2D
High
High for 2D
Low for 3D
Low for 3D
Fiber volume fraction calculation
Unidirectional composites
use the equations described earlier in the
chapter for theoretical calculation
use photomicrographic method
3D composites
Fiber volume fraction calculation
2D composites
Three D woven composite
“ PERFECT” 3D ORTHOGONAL WEAVE
Top view
Side view
Multilayer fabrics
Warp interlock
3D orthogonal
z
Warp (x)
Angle interlock
Filling (y)
2d woven fabrics
二维正交
二维三向
3D - shaped weft-knitted fabrics for preforms
Altering the number of operating needles from course to course
HELMET FORM
3D Theoretical form
2D pattern
Knitted fabric
(Aramid fiber)
2d braiding
3d braiding