Composite materials: what is it, properties, production and application

In various industries, composite materials are used. What it is? These materials are based on several components, which determines their operational and technological characteristics. The basis of the composites is a matrix based on metal, polymer or ceramics. Additional reinforcement is performed by fillers in the form of fibers, whiskers and various particles.

Composites - the future?

Plasticity, strength, 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 substrate. To strengthen the material, threads, fibers, flakes of greater strength are used. Among the composite materials, one can distinguish plastic that is reinforced with boron, carbon, glass fibers, or aluminum, reinforced with steel or beryllium threads. If you combine the content of components, you can obtain composites of different strength, elasticity, resistance to abrasives.

Basic Types

The classification of composites is based on their matrix, which can be metallic and non-metallic. Materials with a metal matrix based on aluminum, magnesium, nickel and their alloys acquire additional strength due to fibrous materials or refractory particles that do not dissolve in the base metal.

Composites with a non-metallic matrix in the base have polymers, carbon or ceramics. Among the polymer matrices, epoxy, polyamide and phenol formaldehyde are most popular. The form of the composition is given by a matrix, which acts as a kind of binding substance. To strengthen the materials used fibers, bundles, threads, multi-layer fabrics.

The manufacture of composite materials is based on the following technological methods:

• Impregnation of reinforcing fibers with matrix material;
• Molding in the mold of reinforcing tape and matrix;
• Cold pressing of components with further sintering;
• Electrochemical coating of fibers and further pressing;
• Deposition of the matrix by plasma deposition and subsequent reduction.

What reinforcer?

In many industries, composite materials have found application. What is it, we already said. These materials are based on several components, which are necessarily hardened by special fibers or crystals. The strength of the composites themselves depends on the strength and elasticity of the fibers. Depending on the type of reinforcing agent, all composites can be divided:

• On fiberglass;
• Carbon fiber with carbon fibers;
• Boron fiber;
• Organic fibers.

Strengthening materials can be stacked in two, three, four or more threads, the more of them, the stronger and more reliable the composite materials will be in operation.

Wood composites

Separately it is worth mentioning wood composite. It is obtained by combining raw materials of different types, with wood 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 - they are in the composition of the material up to 5%.

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 differs in density (its index is affected by the base resin and density of wood particles), good resistance to bending. The material is eco-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 acquires a high level of wear resistance and moisture resistance. It can be used for finishing 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 materials of this type, one can note wood chipboards, fiberboards of different density, plates from oriented chips and wood-polymer composites. The production of composite materials of this type is carried out in several stages:

1. Wood is crushed. For this, crushers are used. After crushing, the wood is sieved and divided into fractions. If the moisture content of raw materials is above 15%, it must be dried.
2. Dosage and mixing of the main components in certain proportions.
3. The finished product is pressed and formatted to obtain a presentation.

Main characteristics

We described the most popular polymer composite materials. What is it is now clear. Due to the laminated 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, the composites have a high resistance to tensile stresses.

Composites based on metals are distinguished by their high strength and heat resistance, while they are practically inelastic. Due to the structure of the fibers, the speed of crack propagation decreases, which sometimes appear in the matrix.

Polymeric materials

Polymer composites are represented in a variety of options, which opens up great opportunities for their use in various fields, from dentistry to the production of aviation equipment. Filling of composites based on polymers is performed by different substances.

The most promising areas of use can be considered construction, oil and gas industry, production of road and rail transport. It is on the share of these industries account for about 60% of the volume of use of polymer composite materials.

Due to the high resistance of polymeric composites to corrosion, the even and dense surface of products that are obtained by molding, the reliability and durability of operation of the final product is increased.

Consider the popular types of polymer materials.

Fiberglass plastic

To reinforce these composite materials, glass fibers molded from molten inorganic glass are used. The matrix is based on thermoactive synthetic resins and thermoplastic polymers, which are distinguished by high strength, low thermal conductivity, high electrical insulating properties. Initially, they were used in the manufacture of antenna fairings in the form of domed structures. In the modern world, GRP is widely used in the construction, shipbuilding, household appliances and sports items, and radio electronics.

In most cases, fiberglass is produced on the basis of sputtering. This method is particularly effective for small- and medium-series production, for example, hulls, boats, cabins for motor vehicles, railway cars. The technology of spraying is convenient because it is not necessary to cut glass material.

Carbon-based plastics

The properties of composite materials based on polymers make it possible to use them in a variety of areas. In them, as a filler, carbon fibers, obtained from synthetic and natural fibers based on cellulose, pitch, are used. The fiber is thermally processed in several stages. Compared with fiberglass, CFRPs have a lower density and a higher modulus of elasticity with ease and strength of the material. Due to their unique operational properties, CFRPs are used in machine and rocket engineering, space and medical equipment manufacturing, bicycles and sports accessories.

Boroplasty

These are multicomponent materials, based on boron fibers introduced into the thermosetting polymer matrix. The fibers themselves are monofilament, bundles, which are intertwined with an auxiliary glass thread. The high hardness of the yarns ensures the strength and durability of the material to aggressive factors, but at the same time the boroplastics are brittle, which complicates the processing. Boron fibers are expensive, so the scope of the use of boroplastics is limited mainly by the aviation and space industries.

Organoplasty

In these composites as the fillers are mainly synthetic fibers - bundles, threads, fabrics, paper. Among the special properties of these polymers, low density, lightness in comparison with glass and carbon plastics, high tensile strength and high resistance to impact and dynamic loads can be noted. This composite material is widely used in such areas as machine-building, shipbuilding, automotive industry, in the production of space technology, chemical engineering.

What is the effectiveness?

Composite materials due to the unique composition can be used in a variety of areas:

• In aviation when producing parts of aircraft and engines;
• Space technology for the production of power structures for apparatus that undergo heating;
• Automotive industry for the creation of lightweight bodies, frames, panels, bumpers;
• Mining industry in the production of drilling tools;
• Civil construction for the creation of span of bridges, elements of prefabricated structures on high-rise structures.

The use of composites allows to increase the power of engines, power plants, while reducing the mass of machinery and equipment.

What prospects?

According to representatives of the industry of Russia, the composite material belongs to the materials of the new generation. It is planned that by 2020 the volumes of domestic production of the composite industry will grow. Already, pilot projects aimed at developing composite materials of a new generation are being implemented on the territory of the country.

The use of composites is advisable in a variety of areas, but it is most effective in high-tech industries. For example, today no aircraft is created without using composites, and some of them use about 60% of polymer composites.

Due to the possibility of combining different reinforcing elements and matrices, it is possible to obtain a composition with a certain set of characteristics. And this, in turn, makes it possible to apply these materials in various fields.