TABLE OF CONTENTS Composite materials or more simply composites can be defined as materials resulting from the association of a continuous phase known as a matrix and a dispersed phase called strengthening, directed in a specific manner and mainly contributing mechanically. Thus wood may be considered as a natural example of a composite, lignin matrix strengthened with cellulose fiber.
The matrix is meant to ensure the cohesion of the material on its whole, i.e.:
to maintain the bond between the strengthening agent and their respective positions;
to protect them with respect to the external environment: humidity, chemical attacks, abrasion and in that case, if it refers to a viscoelastic material such as in the case of organic polymers, to limit the risk of damage by the absorption of energy received and delayed restitution;
to distribute stress and give the external shape to the part.
Matrices could be mineral (ceramic, mortar, concrete), metal (aluminium for example) or organic in nature. In the latter case, we can distinguish between flexible matrix composites (thermoplastic resins, elastomers, bitumen modified or not by polymers) and rigid matrix composites (thermosetting resins or thermosets; see section 1.4.1).
In everyday language, when we speak of composite without specifying the nature of the matrix, we generally refer to organic matrix composites [DAV 87].
The strengthening agent essentially plays a mechanical role. It brings rigidity and mechanical strength and can be set as per preferred orientation (it could be one, two...
