An armouring is applied to a material with the aim of improving its mechanical properties. The armoured material obtained is then a composite. As an example, we mention iron reinforcement in concrete. In plastics, glass fibres are often used to arm the plastic. This makes the material stronger, which means an increase in tensile strength and thus the maximum stress the material can bear. Glass fibres are characterised by a very high tensile strength, but are also ductile. Moreover, the fibres are resistant to high temperatures.