Engineering Materials Classification

Introduction

• 5 classifications of engineering materials: metals, ceramics, polymers, composites, and advanced materials
• Focus on metals, ceramics, polymers, and composites

1. Metals

• Types:
  • Metallic elements: Pure metals (e.g., copper, aluminium, iron, titanium, silver, gold)
  • Metal alloys: Mixtures of metals or metal and non-metal
    • Examples: Brass (copper + zinc), Bronze (copper + tin), Steel (iron + carbon)
  • Ferrous vs Non-ferrous:
    • Ferrous metals: Contain iron (e.g., cast iron, steel, stainless steel)
    • Non-ferrous metals: Do not contain iron (e.g., copper, aluminium, tin, brass, bronze)

2. Ceramics

• Classification: Oxides, nitrides, and carbides
  • Oxides: Silicon oxide (e.g., glass)
  • Nitrides: Silicon nitride (e.g., bearings)
  • Carbides: Silicon carbide (e.g., grinding discs)

3. Polymers

• Often referred to as plastics
• Composition: Chains of hydrocarbons (hydrogen + carbon)
• Types:
  • Thermoplastics: Can be melted and reformed (recyclable, e.g., plastic bottles)
  • Thermosetting plastics: Cannot be remelted once formed (e.g., electrical socket fascias)

4. Composites

• Combination of two or more materials to combine properties
• Examples:
  • Reinforced concrete: Concrete + steel reinforcement
  • GFRP: Glass fibre reinforced polymer
  • CFRP: Carbon fibre reinforced polymer
  • Kevlar composite: Used in body armor, resistant to penetration

General Properties of Material Classes

Metals

• Low elasticity/high stiffness
• High strength
• Malleable and ductile
• High density
• Good conductors of heat and electricity
• High magnetic permeability

Ceramics

• Low elasticity
• High strength
• Very hard but brittle
• High melting points
• Low heat and electrical conductivity (insulators)

Polymers

• High elasticity
• Low strength
• Low density and weight
• Low melting points
• Insulators of electricity and heat
• Highly unreactive

Composites

• Properties depend on parent materials
• High strength-to-weight ratio (e.g., GFRP, CFRP, Kevlar composite)

Conclusion

• Overview of five material classifications and their properties
• Future exploration of chemical bonding and material structures