Fibre Arrangement

Question 1

What does lamina mean?

Answer 1

Individual layer (normally unidirectional).

Question 2

What does Laminate mean?

Answer 2

Material made of stacked lamina.

Question 3

What does Roving mean?

Answer 3

Bundle of fibres held together (normally by weak resin)

Question 4

What does Bundle size mean?

Answer 4

Number of fibres per roving (often 2k, 4k up to 12k)

Question 5

What does unidirectional mean?

Answer 5

• All fibres are parallel (in practise less regular).
• Can idealise arrangement as square of hexagonal array.

Question 6

What does Stacking of Laminates mean?

Answer 6

• Notation used for laminates
• Denoted by angle at which fibres run e.g. 0, 90, +45, -45.
• With some stitched and woven fabrics (0 = 90, +45 = -45)
• Notation: [0/90]3s
  (3 is number of layers, in 1 half if symmetrical; s symmetrical about
  mid-plane)

Question 7

What are woven rovings?

Answer 7

• Bundle of fibres woven together.
• Allows handling fabrics.
• Allows draping into non-planar surfaces.

Question 8

Type of weaving?

Answer 8

• Plain
• Twill
• Satin
• Basketweave

Question 9

Properties of plain weaving?

Answer 9

Stability: Good
Drape: Poor
Surface Smoothness: Poor
Mechanical Properties: Moderate
Symmetry: Yes

Question 10

Properties of twill weaving?

Answer 10

Stability: Moderate
Drape: Good
Surface Smoothness: Moderate
Mechanical Properties: Good
Symmetry: Yes

Question 11

Properties of satin weaving?

Answer 11

Stability: Poor
Drape: Very good
Surface Smoothness: Very good
Mechanical Properties: Very good
Symmetry: No

Question 12

What does spread-tow technology and why is it good?

Answer 12

• Spreading fibres into very flat bundles.
• Reduced fibre bend.
• Increase bundle size.
• Keeps fabric weights low.
• Can lead to mechanical improvement for lower weight.

Question 13

What are the advantages of spread tow technology?

Answer 13

1. The spread tow structure makes it possible to achieve thinner laminates.
2. Straighter fibres with reduced crimp optimise and strengthen the composite.
3. Lower crimp reduce the amount of excess plastic, thereby minimising weight.

Question 14

What is stitch bonded fabrics?

Answer 14

• Weaving imposes considerable bend on fibres.
• Leads to rubbing contact and dry spots.
• Using non-woven rovings, held together by thin (polyester) stitching helps.
• Can give increase in strength.
• Often called “Non-crimp fabric (NCF)”

Question 15

What is chopped-strand mat?

Answer 15

• Chopped roving held together by weak resin.
• Lower properties than woven or stitch-bonded.
• Lower fibre volume fractions.
• Lower cost.

Question 16

What is 3d Weaving and Braiding?

Answer 16

• Aims to give less directional properties, with fibres in all direction.
• Still very complex.
• Costly.
• Becoming slightly more common.