AQA GCSE Engineering: Engineering materials, a complete overview of metals, polymers, composites and selection

What the engineering materials topic demands

Engineering materials is the foundation of the whole qualification: every product is made from a material chosen for a reason. AQA tests two linked skills here. First, precise recall of the property words and the common materials. Second, the ability to apply that knowledge by matching a material to what a product must do and justifying the choice. This overview ties together the five dot-point pages in the topic.

Categories and properties

Engineering materials are grouped into metals, polymers, ceramics and composites. We compare them using three families of property. Mechanical properties describe how a material behaves under force: strength (resisting breaking), hardness (resisting scratching and wear), toughness (absorbing impact), ductility (drawn into wire), malleability (pressed into sheet), stiffness and elasticity. Physical properties describe the material on its own: density, electrical and thermal conductivity, melting point and corrosion resistance. Aesthetic properties cover colour, texture and finish. The recurring exam skill is naming the right property and linking it to a product's job.

Metals and alloys

Metals split into ferrous (contain iron, usually rust) and non-ferrous (no iron, resist rust). Learn a few of each with a property and a use: mild steel (tough, cheap, rusts, used for car bodies), cast iron (hard but brittle, engine blocks), aluminium (light, corrosion resistant, drinks cans) and copper (excellent conductor, wiring). An alloy mixes a base metal with other elements to improve a property: stainless steel resists corrosion, brass is hard and attractive, and bronze is tough.

Polymers and composites

Thermoplastics soften and reshape when reheated and can be recycled. Thermosetting polymers set permanently when first cured and cannot be re-melted. A composite combines a reinforcement (strong fibres) with a matrix (a bonding resin) so the result outperforms either part; GRP and CFRP are the key examples, prized for a high strength-to-weight ratio.

Smart, modern and selected materials

Smart materials change a property in response to a stimulus: shape memory alloys (heat), thermochromic and photochromic pigments (heat and light) and piezoelectric materials (pressure). Modern materials such as graphene come from new processing. Finally, material selection pulls it all together: list the product's requirements, match properties, then balance cost, availability, sustainability and aesthetics to justify the best choice.

Check your knowledge

A mix of recall and application questions covering the engineering materials topic. Attempt them under timed conditions, then check against the solutions.

1. Name the four main categories of engineering material. (4 marks)
2. State the difference between hardness and toughness. (2 marks)
3. Explain what an alloy is and give one example with the property it improves. (3 marks)
4. State one difference between a thermoplastic and a thermosetting polymer. (2 marks)
5. Name the two parts of a composite material and say what each does. (2 marks)
6. Name a smart material and state the stimulus it responds to. (2 marks)
7. Give two factors, besides properties, that affect material selection. (2 marks)