Composite materials: what they are and how they are made
Composite materials have become a precious resource for the realization of numerous products since they integrate lightness, mechanical strength and aesthetic performance: indispensable elements in many industrial sectors.
The use of composite materials has taken on significant importance in recent decades, arriving, in some sectors, almost completely replacing metallic, plastic and wooden materials, thanks to their extremely high physical-mechanical properties.
Among the composite materials a leading role is occupied by carbon fiber, a highly innovative material that allows the creation of products with mechanical characteristics that were previously impossible.
Carbon fiber is ideal for example to give new life to a product that is by now mature or to provide a new lever to the marketing function with its “racing” appeal.
Materials consisting of two or more elements are called “composites“. From the union of these elements we obtain a new material that combines the best features of the single elements that compose it. Generally composite materials are made by means of a matrix and a fiber.
For example, reinforced concrete is a composite material as it consists of the iron rod, which has the task of resisting traction, and of the cement matrix which has the task of resisting compression. In the same way, an artifact made of carbon fiber is composed of woven carbon fiber filaments and a resin, the matrix, generally of an epoxy.
The matrix is the “glue” that holds the fiber together and protects it from the effects of the external environment, also allowing to distribute the loads to which the product is subjected.
Composite materials allow the construction of lightweight, durable and energy-efficient structures that can be used in a wide variety of applications.
The aeronautical and aerospace sectors were the reference sectors forerunners in the use of composite materials: the technologies developed in these enviroments can now also be used for everyday applications.
There are different methods for the production of manufactured articles in composite materials.
One of the main, as well as that used in the aeronautical field, is the autoclave process, since it guarantees the best mechanical characteristics on the finished product.
Epi produces with an autoclave cure process
The prepreg fabrics (or fabrics already impregnated with resin / matrix) of carbon fiber or kevlar or other composite material are first cut into shapes. The shapes are rolled into a mold; the mold is then placed in an autoclave and subjected to a care cycle at electronically controlled pressures and temperatures. At the end of the process the finished piece is obtained.
There are numerous types of compound materials.
The first distinction divides the fibers and the matrices into two macro areas, depending on whether they are natural or synthetic.
The most common types of synthetic fibers include carbon fiber, aramid fiber (kevlar) and fiberglass.
Even natural composites, consisting of at least one element of natural derivation, are currently of particular importance. Today, in fact, alternative sources are available compared to traditional fibers; this is the case, for example, of so-called “green” reinforcements, such as hemp, linen or bamboo fibers.
Ultimately, the main feature of composites is to lighten the finished product while simultaneously improving its mechanical characteristics.
This lightness translates into a generalized saving that, depending on the case, can be evaluated in terms of fatigue or energy.
In addition to structural efficiency, composite materials can also be smarter, more functional and more versatile than traditional ones. The combination of new features in composites is considerably easier than with metals and the only obstacle is the boundaries of imagination.