Composites

Composite materials are constructed from two or more constituent materials with significantly different physical or chemical properties.
When combined, these materials produce a ‘composite’ that has characteristics different from the individual components.
The individual components remain distinct within the finished structure, providing a composite with unique synergistic properties.
Components typically involve a reinforcing material and a binding material, commonly referred to as a matrix.
Composite materials can be designed to be strong in tension (a pull), compression (a push), or shear (a slide), depending on the reinforcement and matrix used.

Fibre-reinforced composites (FRCs) have a fibrous material providing strength, bound together by a matrix. Glass fibre and carbon fibre are common reinforcements, with plastics often used as the matrix.
Polymer Matrix Composites (PMCs) are composites with a polymer-based matrix. An example would be carbon-fibre reinforced plastic, where the carbon fibre provides strength and rigidity, and the plastic acts as the binder.
In Metal Matrix Composites (MMCs), a metal is used as the matrix to bond together reinforcement materials, which could be silicon carbide particles or aluminium oxide fibres.
Ceramic Matrix Composites (CMCs) are designed to maintain strength at high temperatures where metals would fail. These are typically used in the engine parts of aeroplanes or in space shuttles.

Composite materials can be moulded into complex shapes, offering advantages over traditional materials in terms of design flexibility.
Layering is a common technique in composites, allowing designers to tailor the properties to specific requirements or directions.
Although composites can offer superior mechanical properties and resilience, they can also be challenging to repair if damaged.
The production and disposal of some composite materials can have significant environmental impact, which should be considered in their use.

The choice of matrix, reinforcement, and manufacturing process can create composites suited to a wide range of applications.
Carbon-fibre reinforced plastics are used in high-performance products like bicycles, boats, and sports cars due to their high strength-to-weight ratio.
Fibreglass is commonly found in boat hulls, swimming pool linings, and panels for vehicles due to its strength, low cost, and resistance to water.
Architectural and infrastructure applications can use composites, such as in bridge construction, where the materials can offer resistance to weathering and heavy loads.
The aerospace industry utilises composites extensively in the construction of both civil and military aircraft. Return to the bullet points on the ‘Ceramic Matrix Composites (CMCs)’ for a reminder of their heat resistant properties.