Intro to Composites wk 1/2

Question 1

What is a composite

Answer 1

” or more physically distinct and mechanically separable materials are mixed to achieve optimal properties of each component

Question 2

what are the 2 phases of a composite

Answer 2

Matrix - continuous
Reinforcement - dispersed

Question 3

What are the properties of the matrix and the reinforcement (generally)?

Answer 3

Matrix - Relatively compliant and tough
Reinforcement - Relatively stiff and brittle

Question 4

What is the function of the Reinforcement?

Answer 4

Bear load in tension

Question 5

What is the function of the Matrix?

Answer 5

• Keeps the reinforcement together and maintains shape
• Transfer stress onto reinforcement
• Protects reinforcement
• Improves properties

Question 6

What are applications of composites?

Answer 6

Aircraft
Wind turbines
Motorsports
Everything

Question 7

What is the Modulus range of Glass-fibre reinforced polymers and where are they used?

Answer 7

10Gpa-40Gpa (tough)
car bodies/bathtubs/boats/cubicles

Question 8

What is the modulus range of Carbon-fibre reinforced polymers and where are they used?

Answer 8

80GPa - 200Gpa (somewhat brittle)
Aircraft/expensive cars/ satelites

Question 9

What is the modulus range for kevlar reinforced ploymers

Answer 9

50Gpa - 140Gpa (very tough)
Bullet proofing/ abrasion protection

Question 10

Summarise injection moulding?

Answer 10

short fibres
better properties than unfilled thermoplastic
Used to make engineering parts

Question 11

Summarise compression moulding?

Answer 11

long or short fibres
thermally shapeable and re-shapeable
not as strong or stiff as thermosetting

Question 12

What are the properties of ceramic matrix composites and applications?

Answer 12

Brittle matrix
Less brittle fibres/particles
amout/brakes for planes and high performance cars

Question 13

What are the properties and applications of metal matrix composites?

Answer 13

Ductile matrix
Brittle high modulus fibres/particles
Carbide tools, armour, brake components

Question 14

What are the 3 types of Composites?

Answer 14

Particulate-reinforced
Fibre-reinforced
Structural

Question 15

What are particulate-reinforced composites?

Answer 15

can be aligned in plane or random
Larger particles on the micron-scale
Smaller particles on the nano-scale

Question 16

What are Fibre-reinforced composites?

Answer 16

Discontinuous or short fibres can be aligned in plane or random
Continuous or long fibres are always aligned

Question 17

What are structural composites?

Answer 17

Laminates
Sandwich panels

Question 18

What are the 6 particulate aspects that effect composite properties?

Answer 18

1. Size
2. Shape (AR)
3. Orientation
4. Volume fraction
5. Distribution and Dispersion
6. Surface treatment

Question 19

How does particulate volume fraction affect stiffness?

Answer 19

a higher volume fraction leads to a higher stiffness
- particulates are almost always stiffer than the matrix

Question 20

What is meant but critical fibre length for effective reinforcement?

Answer 20

• below critical length, the stress never reaches maximum possible
• above critical length, fibres used efficiently
  generally 1mm

Question 21

What is the aspect ratio of short and long fibres?

Answer 21

<15 - short fibres
>15 - long fibres

Question 22

How does fibre allignment affect composite properties?

Answer 22

aligned - Good properties along fibre direction
Random - equal properties all directions