A composite material is made by combining two or more different materials so the product has better properties than either material alone. Examples include reinforced concrete, fibreglass, fibre optics, photochromic glass and superconductors, each chosen because it is stronger, lighter or more resistant than a single material.
This page covers one Form 4 content standard from the Manufactured Substances in Industry chapter: composite materials. The exam asks for a clear definition of a composite material, several named examples with their component materials and improved properties, and the reasoning for why a composite is better than its separate parts. It is a description-and-application topic, so precise examples score the marks.
What a composite material is
A composite material is a material made by combining two or more different materials, a main material (the matrix) and a reinforcing material, so that the resulting product has properties superior to those of the original materials on their own. The point of a composite is to bring together the best features of each part: for example, the strength of one material and the lightness of another.
Common examples and their properties
You should know these standard examples, their components, and the improved property each gains:
- Reinforced concrete, concrete strengthened with steel bars or mesh. Concrete is strong under compression but weak under tension; steel is strong under tension. The composite is strong under both, so it is used in buildings, bridges, pillars and beams.
- Fibreglass (glass-reinforced plastic), glass fibres embedded in plastic/polyester resin. It is light, strong and resistant to corrosion, so it is used for boat hulls, car body panels, storage tanks and helmets.
- Fibre optics, very fine strands of glass or plastic that carry information as pulses of light. They are used in telecommunications and medical instruments, because they transmit large amounts of data quickly with little loss.
- Photochromic glass, glass containing silver halide particles that darken in bright light and become clear again in dim light. It is used in spectacle lenses and car windscreens.
- Superconductor, a material that conducts electricity with almost no resistance at very low temperatures, used in powerful magnets and advanced electronics.
Why composites are used
A composite is chosen because it improves on a single material. The general reasons are that the composite is stronger, lighter, more resistant to heat, corrosion or wear, or able to do something no single material can, such as being strong under both compression and tension. When you justify a composite in an answer, name the property it improves and the use it makes possible.
Worked example
Question. A reinforced concrete beam has a total mass of 500 kg. It contains steel reinforcing bars of total mass 40 kg, and the rest is concrete. Calculate (a) the mass of concrete in the beam and (b) the percentage by mass of steel in the beam.
Step 1, Find the mass of concrete. Mass of concrete = total mass − mass of steel = 500 kg − 40 kg = 460 kg.
Step 2, Set up the percentage. Percentage by mass of steel = (mass of steel ÷ total mass) × 100.
Step 3, Substitute and calculate. = (40 kg ÷ 500 kg) × 100 = 0.08 × 100 = 8 %.
Answer. (a) The mass of concrete is 460 kg. (b) The percentage by mass of steel in the beam is 8 %.
Practice question
Question. (a) Define a composite material. (b) Reinforced concrete is a composite of concrete and steel. Explain, in terms of compression and tension, why it is better than concrete alone. (c) State one use of fibreglass and the property that makes it suitable.
Answer. (a) A composite material is made by combining two or more different materials so that the product has better properties than the original materials on their own. (b) Concrete is strong under compression but weak under tension, while steel is strong under tension; combining them gives a material that is strong under both compression and tension, so it does not crack easily when loaded. (c) Fibreglass is used for boat hulls (or car body panels) because it is light, strong and resistant to corrosion.
Exam tip
Two things earn the marks here: the definition (“two or more materials combined to give better properties”) and, for each example, the pairing of component materials with the improved property. For reinforced concrete, always mention compression and tension, that contrast is the marking point. When asked to justify a composite for a use, do not just name it; state the property (light, strong, corrosion-resistant) that suits it to the job. Avoid vague words like “better” on their own, say why it is better.
Reasoning about composites in the exam
Many composite questions give you a situation and ask which material to choose. The method is the same each time: identify the demands of the use, then pick the composite whose improved property meets them. A boat hull must be light and must not corrode in water, so fibreglass fits. A bridge must carry heavy loads without cracking, so reinforced concrete fits. Spectacle lenses that should darken in sunlight point to photochromic glass. By reasoning from the required property rather than trying to recall a fixed list, you can handle unfamiliar contexts, and you naturally include the justification that higher-mark questions demand. It also helps to remember that a composite is a physical combination, not a chemical compound, the separate materials keep their own identities within the product.
Where this fits
This is content standard 8.4 of the Manufactured Substances in Industry chapter, sitting alongside alloys as another way of engineering better materials. Reinforce it with the chapter revision notes and practise the definition and application questions in the worked examples. In our online 1-to-1 SPM Chemistry lessons, taught in English, from RM50/hr, with a paid one-hour trial, our teachers make sure each composite is paired with its property and use, because that pairing is what earns full marks in 4541.
Quick recap
- A composite combines two or more materials to give better properties than either alone.
- Reinforced concrete = concrete + steel; strong under compression and tension.
- Fibreglass = glass fibre + plastic; light, strong, corrosion-resistant.
- Fibre optics carry data as light; photochromic glass darkens in bright light.
- Always justify a composite by naming the improved property and its use.
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