What are the four main classes of engineering materials?

Four Main Classes of Engineering Materials

1. Metals

   • Structure: Crystalline, usually FCC, BCC, or HCP.

   • Properties: High strength, ductility, toughness, good thermal & electrical conductivity.

   • Examples: Steel, Aluminum, Copper, Titanium.

   • Applications: Construction, automotive, aerospace, electrical wires, machinery.

2. Ceramics

   • Structure: Mostly crystalline, ionic & covalent bonding.

   • Properties: Hard, brittle, high melting point, good wear & corrosion resistance, electrical insulators.

   • Examples: Glass, Alumina, Silicon Carbide, Bricks.

   • Applications: Cutting tools, aerospace tiles, glass windows, electronic insulators.

3. Polymers

   • Structure: Long chain molecules with covalent bonding along chains, van der Waals between chains.

   • Properties: Lightweight, low strength compared to metals, corrosion resistant, low conductivity, easily moldable.

   • Examples: PVC, Nylon, Teflon, Polyethylene.

   • Applications: Packaging, pipes, medical devices, textiles.

4. Composites

   • Structure: Combination of two or more materials (matrix + reinforcement) to improve properties.

   • Properties: Tailored properties, high strength-to-weight ratio, corrosion resistance.

   • Examples: Fiberglass (glass + polymer), Carbon Fiber Reinforced Polymer (CFRP), Concrete (cement + aggregates + steel).

   • Applications: Aircraft bodies, sports equipment, construction, automotive.

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✅ Short Revision Answer (3–4 lines):
The four main classes of engineering materials are Metals, Ceramics, Polymers, and Composites. Metals are strong and conductive, ceramics are hard but brittle, polymers are lightweight and corrosion-resistant, and composites combine materials to achieve superior, tailored properties.