Lecture 4

Question 1

Metals

Answer 1

• Opaque, high reflectivity
• Ductile, malleable
• Prone to fatigue
• Strong
• High densities
• Poor corrosion resistance
• Prone to oxidation

Question 2

Ceramics

Answer 2

• Crystalline
• Strong in compression
• High modulus
• High hardness
• Good abrasion (wear) resistance
• High melting points
• Electrical insulators
• Good corrosion resistance
• Oxides prone to oxidation

Question 3

Glasses

Answer 3

• Amorphous
• Relatively low melting points
• Relatively low melting points

Question 4

Polymers

Answer 4

• Low moduli
• High strengths
• Low- medium toughness
• Low densities
• Creep
• Properties are temperatures dependent
• Thermal and Electrical Insulators
• Non-magnetic
• Corrosion resistant
• Low friction coefficients

Question 5

Elastomers (rubbers)

Answer 5

-Elastic deformation

Question 6

Composites

Answer 6

• Low density
• High modulus
• High strength
• High toughness
• Difficult to form and join
• Can be anisotropic
• Predominantly polymer matrix and ceramic reinforcement

Question 7

Densities

Answer 7

Solid ranges from 1-20 Mg m-3
Metals have the highest
Ceramics are quite low
Polymers are the lowest

Question 8

Melting temperature

Answer 8

Metals and ceramics have high melting temperatures
Polymers are low
Some composites are high
Creep becomes problematic above around 0.4 Tm

Question 9

Modulus

Answer 9

Ceramics have the highest moduli (20-1000 GPa)
Metals are comparable
Polymers are lower (80 MPa - 20 GPa)
Elastomers and foams are the lowest (1-30 MPa)

Question 10

Strength

Answer 10

Ceramics have a high strength in compression (1000-45000 MPa)
Metals are lower and comparable to polymers and composites (10-2000 MPa)

Question 11

Toughness

Answer 11

Metals have a high toughness (1-1000 kJ m-2)
Ceramics have very low toughness (1-1000 J m-2)
Polymers (0.1-10kJ m-2)
Composites show a range (0.2 -1000 kJ m-2)