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Lecture 3: Fibre architecture Lecture 3: Fibre architecture

Lecture 3: Fibre architecture - PowerPoint Presentation

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Lecture 3: Fibre architecture - PPT Presentation

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 12012012 1 Composites properties are strongly dependant on the arrangement and the distribution of fibres ID: 282794

lecture fibre 2012 architecture fibre lecture architecture 2012 arrangements packing fibres fraction properties distribution weight length short orientation laminates

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Slide1

Lecture 3: Fibre architecture

At the end of this lecture you will have an understanding of:Distribution of fibresPacking arrangements of fibresOrientation of fibresLength of fibresDefects

12/01/2012

1Slide2

Composites properties are strongly dependant on the arrangement and the distribution of fibres:

Diameter and lengthVolume fraction Alignment Packing arrangement (distribution)

Lecture 3: Fibre architecture

12/01/2012

2Slide3

Volume fraction and weight fraction:

Depending on the property we want to discuss, we need to consider either type of descriptionVolume fraction is used for most physical properties (strength …)Weight fraction is used for properties such as densityLecture 3: Fibre architecture

12/01/2012

3Slide4

Volume fraction and weight fraction:

Vf = (wf/ρf)/(wf/ρf+ wm/ρm)wf =

vfρf

/(

v

f

ρ

f

+

v

m

ρ

m)With Vf , Vm, wf, wm, ρf, ρm, volume fraction, weight fraction, and density of fibre and matrix

Lecture 3: Fibre architecture

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4Slide5

Fibre packing arrangements:

In unidirectional lamina, fibres are aligned Two ideal models Hexagonal and square packingLecture 3: Fibre architecture

2R

2r

h

2R

2r

h

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5Slide6

Fibre packing arrangements:

Lecture 3: Fibre architecture

2R

2r

h

2R

2r

h

 

 

h

 

h

 

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6Slide7

Fibre packing arrangements:

these ideal arrangement do not occur usually and there is usually clustering of fibres.Properties are then affected because Vf is lowerFor a resin to penetrate a dense pack of fibres is difficult which leads to defects (voids) and lower propertiesLecture 3: Fibre architecture

12/01/2012

7Slide8

Fibre packing arrangements:

Lecture 3: Fibre architecture12/01/20128Slide9

Fibre packing arrangements:

Laminates:Set of plies stacked togetherGood properties within the plane of the pliesPlies can be arranged in a stack to make the properties isotrope

Lecture 3: Fibre architecture

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9Slide10

Fibre packing arrangements:

Laminates:Lecture 3: Fibre architecture

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10Slide11

Fibre packing arrangements:

Laminates are described by their stacking sequenceLecture 3: Fibre architecture

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11Slide12

Fibre packing arrangements:

Woven arrays of fibres:Lecture 3: Fibre architecture

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12Slide13

Fibre packing arrangements:

Knitted arrays of fibres:Lecture 3: Fibre architecture

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13Slide14

Fibre packing arrangements:

Braided arrays of fibres:Lecture 3: Fibre architecture

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14Slide15

Orientation of fibres:

Occurs often during processing Easier with short fibresDependant on strain, viscosity of matrix and fibre lengthLecture 3: Fibre architecture

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15Slide16

Short fibre arrangements:

Orientation is statistically measured by the texture of the composite (distribution of orientations)Lecture 3: Fibre architecture12/01/201216Slide17

Orientation of fibres:

Lecture 3: Fibre architecture12/01/201217Slide18

Short fibre arrangements:

Length is also a distributionLecture 3: Fibre architecture12/01/201218Slide19

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

Lecture 3: Fibre architecture

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19Slide20

Voids:

Appear during manufacturing process, or due to improper impregnation of the resin, orappear during deformation of the compositeMeasured either by direct observations, or by density measurements

Lecture 3: Fibre architecture

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20