Composites

Question 1

Describe the 3 main types of composite.

Answer 1

Particulate - particles of material dispersed within the matrix material.
Fibre - Fibres dispersed within the matrix material.
Laminate - Sheets of material laminated together.

Question 2

Describe the difference between anisotropic and isotropic.

Answer 2

Anisotropic - Properties differ depending on the direction the force is applied in.
Isotropic - Properties of material are the same in all directions.

Question 3

What is the formula for specific strength?

Answer 3

Specific strength = Tensile strength/ Density = Tensile strength/ Specific gravity

Question 4

What is the formula for specific modulus?

Answer 4

Specific modulus = Elastic modulus / density = Elastic modulus / specific gravity.

Question 5

Are narrow or thick fibres preferable in terms of supporting high stress, and why?

Answer 5

Narrower fibres because there are less defects in narrow fibres.

Question 6

What properties will the matrix material of a composite have?

Answer 6

Low cost.

relatively poor specific properties.

Question 7

What is the purpose of the matrix material?

Answer 7

Transfer load to fibres.
Holds fibres in place.
Prevents corrosion or other damage like scratches to the fibres.

Question 8

What are 3 methods of bonding fibre and matrix?

Answer 8

Mechanical, adhesive and reaction.

Question 9

Is the fibre material strong and brittle or weak and ductile?

Answer 9

Strong and brittle.

Question 10

What is the equation for critical fibre length?

Answer 10

Critical fibre length = Fibre strength * Fibre diameter / 2 * Strength of join between fibre and matrix