WHAT IS A COMPOSITE?
A composite material or a composite is a combination of two or more materials which enhance the properties of the individual components. Today, the most common composites are generally a combination of high strength fibers and plastic. Composite products combine the high strength fibers with a lightweight matrix, creating materials with high specific properties. Through careful selection of fiber length, material, architecture and polymer matrix, a wide range of engineering materials can be created.
Fibers provide the mechanical strength of the assembly, while the matrix formed by the polymeric material keeps them fixed in position and direction, fully coating them and protecting them from the external environment. The polymer matrix thus transmits the external loads to the fibers through the surface of the interface, which must have sufficient adhesion so that the relative sliding does not occur.
The graph below illustrates the relationship between the stress and the strain of the reinforcement, the matrix and the compound obtained from the combination of both. Clearly the reinforcement has a much greater mechanical strength than the matrix, so that the bond between them generates a material (composite) of intermediate mechanical properties.
Composites are anisotropic materials so they must have stiffness and resistance through proper arrangement and alignment of the fibers. The fibers must be located in the directions in which are more effective, anticipating all the stresses that can occur in different circumstances, to make the most of the mechanical properties of the composite.
The fiber-reinforced composites have the following characteristics, which can be observed in the graph below:
- Lower weight than metallic alloys to equal resistance
- Higher resistance than common polymers
- Higher Young’s Modulus than polymers
- High cost of processing (currently)
Source: Spanish Association of Composites
