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Lecture 3: Fibre architecture. At the end of this lecture you will have an understanding of: Distribution of fibres Packing arrangements of fibres Orientation of fibres Length of fibres Defects. Lecture 3: Fibre architecture.

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lecture 3 fibre architecture
Lecture 3: Fibre architecture
  • At the end of this lecture you will have an understanding of:
  • Distribution of fibres
  • Packing arrangements of fibres
  • Orientation of fibres
  • Length of fibres
  • Defects
slide2

Lecture 3: Fibre architecture

  • Composites properties are strongly dependant on the arrangement and the distribution of fibres:
    • Diameter and length
    • Volume fraction
    • Alignment
    • Packing arrangement (distribution)
slide3

Lecture 3: Fibre architecture

  • Volume fraction and weight fraction:
    • Depending on the property we want to discuss, we need to consider either type of description
      • Volume fraction is used for most physical properties (strength …)
      • Weight fraction is used for properties such as density
slide4

Lecture 3: Fibre architecture

  • Volume fraction and weight fraction:
  • Vf = (wf/ρf)/(wf/ρf+wm/ρm)
  • wf= vfρf/(vfρf+ vmρm)
  • With Vf , Vm, wf, wm, ρf, ρm, volume fraction, weight fraction, and density of fibre and matrix
slide5

Lecture 3: Fibre architecture

  • Fibre packing arrangements:
    • In unidirectional lamina, fibres are aligned
    • Two ideal models Hexagonal and square packing

2R

2R

2r

2r

h

h

slide6

Lecture 3: Fibre architecture

  • Fibre packing arrangements:

2R

2R

2r

2r

h

h

h

h

slide7

Lecture 3: Fibre architecture

  • Fibre packing arrangements:
    • these ideal arrangement do not occur usually and there is usually clustering of fibres.
    • Properties are then affected because Vf is lower
    • For a resin to penetrate a dense pack of fibres is difficult which leads to defects (voids) and lower properties
slide8

Lecture 3: Fibre architecture

  • Fibre packing arrangements:
slide9

Lecture 3: Fibre architecture

  • Fibre packing arrangements:
    • Laminates:
      • Set of plies stacked together
      • Good properties within the plane of the plies
      • Plies can be arranged in a stack to make the properties isotrope
slide10

Lecture 3: Fibre architecture

  • Fibre packing arrangements:
    • Laminates:
slide11

Lecture 3: Fibre architecture

  • Fibre packing arrangements:
    • Laminates are described by their stacking sequence
slide12

Lecture 3: Fibre architecture

  • Fibre packing arrangements:
    • Woven arrays of fibres:
slide13

Lecture 3: Fibre architecture

  • Fibre packing arrangements:
    • Knitted arrays of fibres:
slide14

Lecture 3: Fibre architecture

  • Fibre packing arrangements:
    • Braided arrays of fibres:
slide15

Lecture 3: Fibre architecture

  • Orientation of fibres:
    • Occurs often during processing
    • Easier with short fibres
    • Dependant on strain, viscosity of matrix and fibre length
slide16

Lecture 3: Fibre architecture

  • Short fibre arrangements:
    • Orientation is statistically measured by the texture of the composite (distribution of orientations)
slide17

Lecture 3: Fibre architecture

  • Orientation of fibres:
slide18

Lecture 3: Fibre architecture

  • Short fibre arrangements:
    • Length is also a distribution
slide19

Lecture 3: Fibre architecture

  • Short fibre arrangements:
    • Length is also a distribution and often described by 2 averages:
      • Length number average: Ln=ΣNiLi/ΣNi
      • Length weight average: Lw=ΣWiLi/ΣWi
slide20

Lecture 3: Fibre architecture

  • Voids:
    • Appear during manufacturing process, or
    • due to improper impregnation of the resin, or
    • appear during deformation of the composite
    • Measured either by direct observations, or by density measurements