2.3 Composite materials
A composite material is made from more than one material component combined together to achieve mechanical properties more desirable than those of either material when used alone. Composites are usually formed by embedding small pieces of one material (reinforcement) into a matrix formed of another material. For example, fibreglass is a composite material consisting of glass fibres embedded in a matrix of polymer resin. Other common fabricated composites are concrete – stone particles in a cement matrix – and plywood – wooden layers in a glue matrix with the grain of the wood in alternating layers crossed.
The reinforcing component in a composite material is often fibrous and is typically used to improve the strength and toughness of the composite. Incorporating the fibres into the matrix in sheets allows the orientations of the fibres within the matrix to be controlled and, coupled with the availability of many different types of fibre, this means that the final product can have a wide range of properties.
However, recent developments in the mass manufacture of composites based on carbon fibres, known collectively as Carbon Fibre Reinforced Polymers (CFRP), have had a massive impact in the aerospace, automotive, marine and sports goods industries as well as the toy industry. This is mainly due to the exceptionally high strength-to-weight ratio of CFRP of around 2457 kN m kg−1, while that for steel is typically 254 kN m kg−1.
The evolution of ultra high-strength sports goods (see Figure 12) and airborne toys, such as drones, is partly due to the recent development of extremely light and yet very strong composite materials like CFRP.