What are composites, smart materials and modern materials, and why are they chosen?
The structure and selection of composite materials (matrix and reinforcement, for example GRP, CFRP, concrete, plywood), the behaviour of smart materials that respond reversibly to a stimulus (shape memory alloys, thermochromic and photochromic pigments, piezoelectric materials, electroluminescent and quantum tunnelling materials), and modern or technical materials developed for new functions (graphene, Kevlar, Gore-Tex, precious metal clay, nanomaterials, technical textiles).
A focused answer to the Edexcel 9DT0 content on composites, smart materials and modern or technical materials, covering matrix-and-reinforcement structure (GRP, CFRP), reversible smart behaviours (shape memory alloys, thermochromics, piezoelectrics) and modern materials such as graphene, Kevlar and Gore-Tex.
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What this dot point is asking
Edexcel wants you to explain the structure of composites (a reinforcement in a matrix) and why they are selected, the reversible behaviour of smart materials that respond to a stimulus, and the modern or technical materials engineered for new functions, with real product examples for each.
The answer
Composites: matrix and reinforcement
Common composites:
- GRP (glass reinforced plastic): glass fibre in polyester resin; boat hulls, car body panels, water tanks, light and corrosion resistant.
- CFRP (carbon fibre reinforced polymer): carbon fibre in epoxy; bike frames, aircraft parts, very light and stiff but expensive.
- Reinforced concrete: steel bars in concrete, adding the tensile strength concrete lacks.
- Plywood and MDF: timber-based composites of veneers or fibres bonded with resin.
Smart materials respond reversibly to a stimulus
- Shape memory alloy (Nitinol): deformed when cool, it returns to a remembered shape when heated past a transition temperature; used in spectacle frames, stents and actuators.
- Thermochromic pigment: changes colour with temperature; used in mood toys, battery testers, kettles and hot-drink warnings.
- Photochromic pigment: darkens in ultraviolet light; used in self-tinting glasses.
- Piezoelectric material: produces a voltage when squeezed and changes shape when a voltage is applied; used in lighters, microphones, knock and impact sensors.
- Electroluminescent material: emits light when a voltage is applied; used in safety strips and displays.
- Quantum tunnelling composite (QTC): insulates until compressed, then conducts; used in pressure-sensitive switches.
Modern and technical materials
Examples in context
Boat builders mould hulls in GRP for a light, watertight, corrosion-free shell, and aircraft and Formula 1 teams use CFRP to cut weight while keeping stiffness on the main load paths. Smart materials appear in everyday safety and convenience: thermochromic warnings on kettles and baby spoons, photochromic self-tinting glasses, and piezoelectric igniters in gas lighters. Technical materials solve specific problems, Gore-Tex jackets keep rain out while letting sweat escape, Kevlar protects against cuts and ballistic impact, and graphene is being developed for stronger, lighter and more conductive products, illustrating how material innovation drives new product functions.
Try this
Q1. State the two parts of a composite and what each does. [2 marks]
- Cue. A reinforcement (fibres or particles) that carries the load, held in a matrix (binder) that bonds it and transfers stress.
Q2. Explain what makes a material "smart". [2 marks]
- Cue. It responds reversibly to an external stimulus (such as heat, light or force) and returns to its original state when the stimulus is removed.
Q3. Give one product use of a shape memory alloy and the stimulus involved. [2 marks]
- Cue. Spectacle frames or stents, which return to their remembered shape when heated above a transition temperature (the stimulus is heat).
Exam-style practice questions
Practice questions written in the style of Pearson Edexcel exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
Edexcel 20204 marksCarbon fibre reinforced polymer (CFRP) is a composite. Explain what is meant by a composite and why CFRP is used for racing bicycle frames.Show worked answer →
Award up to two marks for the meaning of a composite and up to two for justified reasons linked to the frame.
A composite combines two or more different materials, a reinforcement (carbon fibres) held in a matrix (epoxy resin), so that the result has properties superior to either material alone; the fibres carry tensile load and the matrix bonds them, transfers stress and resists compression.
CFRP is used for racing frames because it has an extremely high strength-to-weight ratio and high stiffness, giving a very light yet rigid frame for efficient pedalling, and the lay-up can be tailored so fibres run along the main load paths. Markers reward the matrix-plus-reinforcement idea and a property (strength-to-weight or tailored stiffness) tied to the cycling context.
Edexcel 20226 marksDiscuss how a smart material could improve a product of your choice, explaining how the material responds to its stimulus and the benefit to the user.Show worked answer →
Extended-response item marked on levels (correct smart-material behaviour, a sensible application and a clear user benefit).
A valid answer names a smart material, states the reversible response to a stimulus, and links it to a real benefit. For example, thermochromic pigment in a baby's feeding spoon changes colour above a set temperature, warning a parent the food is too hot, then reverts when it cools; the response is reversible and needs no power.
Alternatively, a shape memory alloy (Nitinol) in spectacle frames returns to its original shape after bending because heat (body or warm water) triggers a reversible phase change, so the frames resist permanent damage. Or piezoelectric material in a sensor generates a voltage when squeezed, used in an impact or knock sensor.
A strong response is specific about the stimulus (heat, force, light) and the reversibility, and judges the benefit (safety, durability, convenience) rather than just naming the material.
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Sources & how we know this
- Pearson Edexcel A-Level Design and Technology: Product Design (9DT0) specification — Pearson Edexcel (2017)