As it has been explained in previous posts, reinforcements in composite materials have the function to carry the load applied to the laminate. Depending on the following factors, the reinforcement would contribute more or less to the composite material mechanical properties:
- The mechanical properties of the fibers: glass, carbon, boron…
- The fraction of volume of the fibers in the composite material between them.*
- The orientation of the fibers
- The interface between the fiber and the matrix.
Note: between 60-70% is an excellent value to achieve the maximum laminate strength, more than that would make difficult to the matrix to hold all the fibers together as it cannot flow correctly among the fibers.
Main type of reinforcements in composite materials
There are 3 types of reinforcements in composite materials that are mainly used:
- Particles:
- Short fibers: used in SMC.
- Long fibers.
Long fiber reinforcements
In the case of long fibers, which are the most commonly used for laminates there are different types too, depending on the final use of the component:
Unidirectional: all the fiber are orientated parallel to one direction.
Woven: fabrics have two threads that are woven together.
- Plain weave: has a low drapeability and high crimp, which gives less better mechanical performance and is more difficult to lay up in complex geometries.
- Twill weave: has an average drapeability and an average crimp.
- Satin weave: has a good drapeability and low crimp.
Recommendations:
- Fabrics that have high drapeability for impact applications.
- Fabrics that have low drapeability for laminate that have loads in compression or flexural.
- Fabrics with thin fibers for tension applications.
- Fabrics with thick fibers for shear applications.
