The definition of composite material is a material usually not present in nature that derrives from the combination of at least two chemically different materials with each other, resulting in an interface separation. Composite materials are used in structures, such as those used on certain aircraft, for their rigidity and lightness, as well as for fatigue, corrosion and impact. Composite materials are distinguished from metals because they are the result of the combination of materials that differ in composition or form. Reinforced concrete is an excellent example of a composite structure allowing concrete and Steel to retain their identity. The Steel bars under load voltage, whilst the cement supports those in compression. The advanced composites are made of high strength fibers embedded in a epoxy matrix. Structures of graphite- epoxy allow a weight saving of 20% compared to aluminum. The reduction in weight is the most obvious benefit to support this choice. Other advantages over traditional materials is that they have high corrosion resistance, and resistance to cyclic loads. The major disadvantage is instead linked to high costs. The hybrid composite mate¬rials are usually obtained by combining glass fibers, kevlar or carbon fiber epoxy resin matrix, to obtain specific characteristics such as resistance to breakage or impact. The fiberglass is by far the most widely used fiber reinforcement, the words GRP (Glass Reinforced Plastic) and FRP (Fiber Reinforced Plastic) are often used to describe products made from composites. The thermosetting resin matrices most commonly used include polyester, epoxy, vinyl ester and phenolic. The choice of types of resins used for adjusting characteristics relating to operating temperature, resistance to chemicals and atmospheric agents, properties, electrical conductivity and resistance to fire. Most of the objects produced with traditional materials can also be produced by using composite materials. While the use of composites is almost an obvious choice for certain applications, the selection of materials to be used is generally a function of life required to finished product, thè total number of parts to be manufactured, thè complexity of form, of savings in assembly costs, and, finally, the experience in thè use of composites. In many cases the best results are obtained by the combined use of composite materials and traditional materials. In recent years the production processes have evolved constantly. Although the application at hand is stili a common technique, new techniques, such as, for example, vacuum infusion are constantly evolving in high technology sectors such as aerospace applications of composite materials.
|Numero di pagine||18|
|Stato di pubblicazione||Published - 2011|