What are modern composites and smart materials, and why are they used?
Composites (GRP, CFRP) and modern/smart materials (shape-memory alloys, thermochromics, piezoelectrics) and their applications.
A CCEA A-Level Technology and Design answer on composite materials such as GRP and carbon-fibre-reinforced polymer, and modern and smart materials including shape-memory alloys, thermochromic and photochromic pigments and piezoelectric materials, with their applications.
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What this dot point is asking
CCEA wants you to explain composites (matrix plus reinforcement) with examples such as GRP and CFRP, and to describe modern and smart materials that change reversibly with a stimulus, naming applications. Expect a definition-plus-application question.
The answer
Composites
Why composites are used
Smart and modern materials
Worked example: choosing a smart material for a function
Examples in context
Example 1. Wind-turbine blades. Made from GRP (and carbon for the spar) because the blade must be light, very long and stiff yet weatherproof for decades, a job no single material does well, which is the case for a composite.
Example 2. Gas-hob igniter. Pressing the knob squeezes a piezoelectric crystal, generating a high voltage that sparks the gas, a direct everyday use of stress-to-voltage conversion in a smart material.
Try this
Q1. Name the two parts of a composite material. [2 marks]
- Cue. A matrix (binder) and a reinforcement (fibres/load-carrying phase).
Q2. Give one advantage and one disadvantage of CFRP for a racing bicycle. [2 marks]
- Cue. Advantage: very high stiffness-to-weight, so it is light and responsive. Disadvantage: expensive and hard to recycle (or can fail suddenly).
Q3. Describe how a photochromic material behaves. [2 marks]
- Cue. It darkens in UV/bright light and returns to clear when the light is removed, a reversible change.
Exam-style practice questions
Practice questions written in the style of CCEA exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
CCEA 20206 marksExplain what is meant by a composite material, using carbon-fibre-reinforced polymer as an example, and give two reasons composites are chosen for sports equipment.Show worked answer →
A composite combines two or more different materials so that the result has properties superior to those of the constituents on their own. It has a matrix (a binding material) and a reinforcement (a stronger, stiffer phase). In carbon-fibre-reinforced polymer (CFRP) the matrix is an epoxy (thermosetting) resin and the reinforcement is carbon fibres: the fibres carry the load (very high strength and stiffness) while the resin holds them in place, transfers load between them and protects them.
Two reasons composites suit sports equipment: (1) an excellent strength-to-weight (and stiffness-to-weight) ratio, so a racing bike, tennis racket or hockey stick is light yet stiff for fast response; and (2) the ability to tailor properties directionally by aligning the fibres along the lines of stress, and to mould complex aerodynamic shapes in one piece.
Markers reward the matrix-plus-reinforcement definition, the correct constituents of CFRP, and two valid, explained reasons (strength-to-weight and tailorable/mouldable being the strongest).
CCEA 20184 marksDescribe one smart material and explain how its property change could be used in a product.Show worked answer →
A shape-memory alloy (SMA) such as Nitinol (nickel-titanium) can be deformed when cool but returns to a pre-set "remembered" shape when heated above a transition temperature. Use: in a fire-safety sprinkler or a thermostatic valve, the SMA element changes shape at a set temperature to open or close the flow automatically; or in spectacle frames, it springs back after being bent.
Alternatively: a thermochromic pigment changes colour with temperature (used in a kettle or baby-bath strip that shows when water is too hot); a photochromic pigment darkens in UV (sunglasses); a piezoelectric material generates a voltage when stressed (sensors, igniters).
Markers want one smart material correctly described (the reversible stimulus-response) and a sensible product application that exploits the change.
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Sources & how we know this
- CCEA GCE Technology and Design specification — CCEA (2016)