Composites or fiber-reinforced composites consist of at least two macroscopically differentiable materials that are combined with the basic aim of improving the material properties. A fiber structure is usually embedded in a resin (matrix material) and then cured.
To achieve this, fibers and fiber bundles are processed into a textile or fabric. Most methods to manufacture fabrics from fibers have originated from the textile industry, hence, most of the terminology used in this field is also used in the context of processing reinforcing fibers into textiles. The fibers determine the composite’s strength and stiffness. A material into which aligned fibers have been incorporated can be much stronger in the fiber direction than the same material without fibers. The increase in stiffness is less pronounced when force is exerted perpendicular to the orientation of the fibers. The strength in this direction is lower since the fibers act as concentrators of stress. In practice, fibers aligned in different directions are often incorporated.
There are many possible designs*:
Unidirectional fibers Bidirectional fibers Short fibers
The graph below shows the fiber’s contribution to a composite’s strength: