Textile structures for composites
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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




    PERFECT” 3D ORTHOGONAL WEAVE

    Top view

    Side view


    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


    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


    2 d braiding
    2d braiding



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