What is a composite material?
A composite material is made by combining two or more different materials to produce a new material with improved properties — properties that are better than those of the individual components. The materials do not dissolve or merge into each other; each keeps its own identity but works together.
Most composites have two parts: a matrix (the continuous material that holds everything together) and a reinforcement (fibres or particles that give strength). The reinforcement carries the load while the matrix protects it and holds it in shape.
Key idea
A composite combines the best of each part: for example strong but brittle fibres in a flexible matrix give a material that is strong, light and tough — better than either material alone.
Common examples
| Composite | Made from | Improved property |
| Reinforced concrete | Concrete + steel bars | Withstands both compression and tension |
| Fibreglass | Glass fibre + plastic | Strong, light, does not rust |
| Photochromic glass | Glass + silver compounds | Darkens in bright light |
| Fibre-reinforced polymer | Carbon/glass fibre + polymer | Very strong and very light |
Why composites are useful
Plain concrete is strong when squeezed (compression) but weak when stretched (tension), so it cracks. Adding steel bars, which are strong in tension, makes reinforced concrete that resists both forces — perfect for bridges and buildings. Fibreglass and carbon-fibre composites are used in boats, cars and aircraft because they are strong yet light and do not corrode.
Worked example
Why is steel added to concrete? Concrete is strong in compression but weak in tension. Steel is strong in tension. Combining them gives reinforced concrete that is strong under both compression and tension, so beams and pillars do not crack under load.
Remember
- A composite = two or more materials combined for better properties.
- Reinforced concrete = concrete (compression) + steel (tension).
- Fibreglass and carbon fibre = strong, light and corrosion-free.