In various industries, composite materials are used. What it is? These are materials based on several components, which determines their operational and technological characteristics. Composites are based on a matrix based on metal, polymer or ceramic. Additional reinforcement is performed by fillers in the form of fibers, whiskers and various particles.
Is the future for composites?
Plasticity, strength, a wide scope of application - this is what distinguishes modern composite materials. What is this in terms of production? These materials consist of a metallic or non-metallic base. To strengthen the material used threads, fibers, flakes of greater strength. Among composite materials, one can distinguish plastic, which is reinforced with boron, carbon, glass fibers, or aluminum, reinforced with steel or beryllium filaments. If you combine the content of the components, you can get composites of different strength, elasticity, resistance to abrasives.
Main types
The classification of composites is based on their matrix, which can be metallic or non-metallic. Materials with a metal matrix based on aluminum, magnesium, nickel and their alloys gain additional strength due to fibrous materials or refractory particles that do not dissolve in the base metal.
Non-metallic matrix composites are based on polymers, carbon or ceramics. Among the polymer matrices, the most popular are epoxy, polyamide and phenol formaldehyde. The form of the composition is attached due to the matrix, which acts as a kind of binder. For hardening materials, fibers, tows, threads, multilayer fabrics are used.
Composite materials are manufactured on the basis of the following technological methods:
- impregnation of reinforcing fibers with matrix material;
- molding in the mold of hardener and matrix tapes;
- cold pressing of components with further sintering;
- electrochemical coating of fibers and further pressing;
- matrix deposition by plasma spraying and subsequent compression.
Which hardener?
Composite materials have found application in many industries. What is it, we have already said. These are materials based on several components that are necessarily reinforced with special fibers or crystals. The strength and elasticity of the fibers also determine the strength of the composites themselves. Depending on the type of hardener, all composites can be divided:
- on fiberglass;
- carbon fiber carbon fibers;
- boron fiber;
- fiberglass.
Hardening materials can be stacked in two, three, four or more threads, the more they are, the stronger and more reliable the composite materials will be in operation.
Wood composites
Separately, it is worth mentioning a wood composite. It is obtained through a combination of different types of raw materials, while wood acts as the main component. Each wood-polymer composite consists of three elements:
- particles of crushed wood;
- thermoplastic polymer (PVC, polyethylene, polypropylene);
- complex of chemical additives in the form of modifiers - up to 5% of them in the composition of the material.
The most popular type of wood composites is a composite board. Its uniqueness lies in the fact that it combines the properties of both wood and polymers, which significantly expands the scope of its application. So, the board is notable for its density (base resin and density of wood particles influence its index), good bending resistance. At the same time, the material is environmentally friendly, preserves the texture, color and aroma of natural wood. The use of composite boards is absolutely safe. Due to polymer additives, the composite board gains a high level of wear resistance and moisture resistance. It can be used to decorate terraces, garden paths, even if they have a heavy load.
Production Features
Wood composites have a special structure due to the combination of a polymer base with wood in them. Among the materials of this type, one can note wood-particle, wood-fiber boards of different densities, oriented wood chips and wood-polymer composite. The production of composite materials of this type is carried out in several stages:
- Chopped wood. For this, crushers are used. After crushing, the wood is sieved and divided into fractions. If the moisture content of the raw material is above 15%, it must be dried.
- The main components are dosed and mixed in certain proportions.
- The finished product is pressed and formatted to gain marketability.
Main characteristics
We have described the most popular polymer composite materials. What it is is now clear. Due to the layered structure, it is possible to reinforce each layer with parallel continuous fibers. It is worth mentioning separately about the characteristics of modern composites, which differ:
- high value of temporary resistance and endurance limit;
- high level of elasticity;
- strength, which is achieved by reinforcing the layers;
- Due to the hard reinforcing fibers, composites are highly resistant to tensile stress.
Composites based on metals are characterized by high strength and heat resistance, while they are practically inelastic. Due to the structure of the fibers, the propagation speed of cracks that sometimes appear in the matrix is reduced.
Polymer materials
Polymer composites are presented in a variety of options, which opens up great opportunities for their use in various fields, ranging from dentistry to the production of aircraft. The filling of composites based on polymers is performed by different substances.
The most promising areas of use are construction, the oil and gas industry, and the production of automobile and railway transport. It is these industries that account for about 60% of the use of polymer composite materials.
Due to the high resistance of polymer composites to corrosion, the even and dense surface of products obtained by molding, the reliability and durability of the operation of the final product are increased.
Consider the popular types of polymeric materials.
Fiberglass
Glass fibers formed from molten inorganic glass are used to reinforce these composite materials. The matrix is based on thermosetting synthetic resins and thermoplastic polymers, which are distinguished by high strength, low thermal conductivity, high electrical insulation properties. Initially, they were used in the manufacture of antenna fairings in the form of domed structures. In the modern world, fiberglass is widely used in the construction industry, shipbuilding, production of household equipment and sports items, radio electronics.
In most cases, fiberglass is made on the basis of spraying. This method is especially effective in small- and medium-series production, for example, hulls for boats, boats, cabins for automobile transport, railway cars. The spraying technology is convenient for cost-effectiveness, since glass material does not need to be cut.
CFRP
The properties of polymer-based composite materials make it possible to use them in a wide variety of fields. They use carbon fibers as filler obtained from synthetic and natural fibers based on cellulose, pitch. The fiber is thermally processed in several stages. Compared to fiberglass, carbon fiber has a lower density and a higher modulus of elasticity with lightness and strength of the material. Due to the unique operational properties of carbon fiber, they are used in machine and rocket science, the production of space and medical equipment, bicycles and sports equipment.
Boroplasty
These are multicomponent materials based on boron fibers introduced into a thermosetting polymer matrix. The fibers themselves are represented by monofilaments, tows that are braided with auxiliary glass thread. The high hardness of the threads provides strength and resistance of the material to aggressive factors, but at the same time, boroplastics are brittle, which complicates the processing. Boron fibers are expensive, so the scope of boroplastics is limited mainly to the aviation and space industries.
Organoplasty
In these composites, fillers are mainly synthetic fibers - tows, threads, fabrics, paper. Among the special properties of these polymers are low density, lightness compared with glass and carbon fiber reinforced plastics, high tensile strength and high resistance to impact and dynamic loads. This composite material is widely used in such fields as engineering, shipbuilding, automotive engineering, in the production of space technology, and chemical engineering.
What is the effectiveness?
Composite materials due to their unique composition can be used in a variety of fields:
- in aviation in the manufacture of aircraft parts and engines;
- space technology for the production of power structures of vehicles that are heated;
- automotive industry to create lightweight bodies, frames, panels, bumpers;
- mining industry in the manufacture of drilling tools;
- civil engineering to create spans of bridges, prefabricated elements on high-rise buildings.
The use of composites allows you to increase the power of engines, power plants, while reducing the mass of machines and equipment.
What are the prospects?
According to representatives of the Russian industry, composite material refers to materials of a new generation. It is planned that by 2020 the volume of domestic production of composite products will increase. Pilot projects aimed at developing a new generation of composite materials are already being implemented in the country.
The use of composites is advisable in a variety of fields, but it is most effective in industries related to high technology. For example, today no aircraft can be created without the use of composites, and some of them use about 60% of polymer composites.
Due to the possibility of combining various reinforcing elements and matrices, you can get a composition with a specific set of characteristics. And this, in turn, makes it possible to use these materials in various fields.