Most composite materials have two components:
The table shows some examples of composite materials.
|Fibreglass||Glass fibres||Polymer resin|
|Carbon fibre reinforced polymer||Carbon fibres||Polymer resin|
|Chipboard||Wood chips||Resin glue|
It is often possible to separate the reinforcement from the matrix by physical processes. For example, concrete can be broken up using machinery. This is one stage in recycling the components of concrete.
The properties of concrete can be improved by reinforcing it with steel rods or mesh. The compressive strength of concrete is higher than its tensile strength, but the tensile strength of steel is higher than its compressive strength. The combination of the two creates a material that is strong in tension and in compression. This allows reinforced concrete to be strong and slightly flexible, which is important when constructing large buildings and structures.
Fibres are embedded in a polymer matrix. The fibres can be made of glass (fibreglass), aramid (Kevlar) and carbon (graphite). These composites are often used for sporting equipment such as tennis rackets and hockey sticks.
The fibres in these composite materials have a low density. They are strong in tension, so they are not easily stretched, but they are flexible. The polymer resin, which binds the fibres together, is not strong but it is stiff. The composite materials show a combination of these properties. They are strong, stiff and lightweight.