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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.

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objectives
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 composites1
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 composites2
Textile Structures for Composites
  • Unidirectional
    • Laminae (ply)
      • Laminates: a stack of laminae
textile structures for composites3
Textile Structures for Composites
  • Two dimensional (Laminates)
      • Nonwoven:
        • short fibers and continuous fibers, plates,
        • particulates
      • Woven
        • Biaxial
        • Triaxial
        • Knitted
        • Braided
textile structures for composites4
Textile Structures for Composites
  • Three dimensional
      • Nonwoven
      • Woven
        • Orthogonal
        • Multi-directional
        • Knitted
        • Braided
      • Combination
textile structures for composites5
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
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 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 preforms1
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
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 textiles1
Three dimensional textiles
  • Knitted and braided forms
    • Weft knitting
    • Warp knitting
      • with weft insertion
      • multiaxial warp knitting
    • 3D braiding
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
braiding1
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
3D-Braiding
  • 4-Step Braiding
    • Original
  • Step 1
  • Step 2
  • Step 3
  • Step 4
braiding2
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
braiding3
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
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 composites1
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
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 d1
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 d2
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
fiber volume fraction calculation
Fiber volume fraction calculation
  • Unidirectional composites
    • use the equations described earlier in the chapter for theoretical calculation
    • use photomicrographic method
  • 3D composites
multilayer fabrics
Multilayer fabrics

Warp interlock

3D orthogonal

z

Warp (x)

Angle interlock

Filling (y)

2d woven fabrics
2d woven fabrics

二维正交 二维三向

slide33

3D - shaped weft-knitted fabrics for preforms

Altering the number of operating needles from course to course

HELMET FORM

Knitted fabric

(Aramid fiber)

3D Theoretical form

2D pattern

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