Lecture 1

Question 1

What is a composite material?

Answer 1

A combination of two or more distinct materials to enhance properties. Constituents have different properties and presence. Reinforcement and matrix are separated by a distinct interface.

Question 2

What is a fibre reinforcement layer made up of?

Answer 2

A single layer either continuous or discontinuous fibre.

Continuous can be unidirectional, bidirectional or woven.

Discontinuous can be random orientation or preferred orientation.

Question 3

What is the 3 different scales in composites?

Answer 3

Micromechaincs: fibre to matrix 110^-6 to 110^-5 metres

Macromechanics: Ply to lamina 110^-4 to 110^-2 metres

Mechanics: Structural parts to aircraft 110^-1 to 110^3 metres

Question 4

How is the strength of brittle materials determined?

Answer 4

They are dominated by “Griffith Flaws”: ultimate strength is proportional to the square root inverse of the crack length a.

Question 5

What are the different types of carbon fibres?

Answer 5

PAN and PITCH

PAN has higher strength and failure strain.

PITCH has higher modulus and zero thermal expansion along the fibre direction.

Question 6

What are the six advantages of composites?

Answer 6

Good properties (Light Weight, Strength, Stiffness)
Anisotropic (Opportunity to tailor material)
Electrical and thermal insulation
Good durability (Corrosion resistant)
Dimensional stability (Maintains shape when heated or wet)
Easily shaped (Manufacturable)