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The use of composite materials. Obtaining polymer composite materials

Composite materials - artificially created materials that consist of two or more components that differ in composition and are separated by a pronounced boundary, and which have new properties designed in advance.

The components of the composite material are different geometrically. A component that is continuous throughout the entire volume of a composite material is called matrix. A discontinuous component separated in the volume of a composite material is called fittings. The matrix gives the required shape to the product, affects the creation of the properties of the composite material, protects the reinforcement from mechanical damage and other environmental influences.

Organic and inorganic polymers, ceramic, carbon and other materials can be used as matrices in composite materials. The properties of the matrix determine the technological parameters of the process of obtaining the composition and its: density, specific strength, operating temperature, resistance to fatigue failure and exposure to aggressive media. Reinforcing or reinforcing components are evenly distributed in the matrix. They, as a rule, have a high , and in these indicators they significantly exceed the matrix. Instead of the term reinforcing component, the term filler can be used.

Classification of composite materials

According to the geometry of the filler, composite materials are divided into three groups:

with zero-dimensional fillers whose dimensions in three dimensions are of the same order;
with one-dimensional fillers, one of the dimensions of which significantly exceeds the other two;
with two-dimensional fillers, two dimensions of which are significantly larger than the third.

According to the arrangement of fillers, three groups are distinguished composite materials:

with a uniaxial (linear) arrangement of the filler in the form of fibers, threads, whiskers in the matrix parallel to each other;
with a biaxial (planar) arrangement of the reinforcing filler, whisker mats, foil in the matrix in parallel planes;
with a triaxial (volumetric) arrangement of the reinforcing filler and the absence of a predominant direction in its location.

According to the nature of the components, composite materials are divided into four groups:

composite materials containing a component of metals or alloys;
composite materials containing a component of inorganic compounds of oxides, carbides, nitrides, etc.;
composite materials containing a component of non-metallic elements, carbon, boron, etc.;
composite materials containing a component of organic compounds of epoxy, polyester, phenolic, etc.

The properties of composite materials depend not only on the physicochemical properties of the components, but also on the strength of the bond between them. Maximum strength is achieved if or occurs between the matrix and the reinforcement.

In composite materials with zero-dimensional filler the most widely used metal matrix. Compositions on metal base are strengthened by uniformly distributed dispersed particles of various fineness. These materials are different.

In such materials, the matrix perceives the entire load, and the dispersed particles of the filler prevent the development of plastic deformation. Effective hardening is achieved at a content of 5...10% filler particles. Reinforcing fillers are particles of refractory oxides, nitrides, borides, carbides. Dispersion-strengthened composite materials are obtained by powder metallurgy methods or reinforcing powder particles are introduced into a liquid metal or alloy melt.

Composite materials based on, reinforced with particles of aluminum oxide (Al 2 O 3), have found industrial application. They are obtained by pressing aluminum powder followed by sintering (SAP). The advantages of SAP appear at temperatures above 300 o C, when aluminum alloys soften. Dispersion hardened alloys retain the effect of hardening up to a temperature of 0.8 T pl.

SAP alloys are satisfactorily deformed, easily machined, welded and. Semi-finished products are produced from SAP in the form of sheets, profiles, pipes, foil. They are used to make blades of compressors, fans and turbines, piston rods.

In composite materials with one-dimensional fillers hardeners are one-dimensional elements in the form of whiskers, fibers, wire, which are held together by a matrix into a single monolith. It is important that the strong fibers are evenly distributed in the plastic matrix. For the reinforcement of composite materials, continuous discrete fibers with dimensions of cross section from fractions to hundreds of micrometers.

Materials reinforced with whiskers were created in the early seventies for aviation and space structures. The main way to grow whiskers is to grow them from supersaturated steam (PC process). For the production of especially high-strength whiskers of oxides and other compounds, growth is carried out according to the P-L-C - mechanism: the directed growth of crystals occurs from a vapor state through an intermediate liquid phase.

Filamentary crystals are created by drawing liquid through spinnerets. The strength of the crystals depends on the cross section and the smoothness of the surface.

Composite materials of this type are promising as. To increase the efficiency of heat engines, gas turbine blades are made of nickel alloys reinforced with sapphire filaments (Al 2 O 3), this makes it possible to significantly increase the temperature at the turbine inlet (the tensile strength of sapphire crystals at a temperature of 1680 o C is above 700 MPa).

Reinforcement of rocket nozzles from powders of tungsten and molybdenum is produced with sapphire crystals both in the form of felt and individual fibers, as a result of which it was possible to double the material at a temperature of 1650 o C. Reinforcement of the impregnating polymer of glass-textolites with filamentous fibers increases their strength. Cast metal reinforcement reduces it in structures. It is promising to strengthen glass with unoriented whiskers.

To reinforce composite materials, metal wire from different metals is used: steel different composition, tungsten, niobium, - depending on the operating conditions. steel wire processed into woven meshes, which are used to obtain composite materials with reinforcement oriented in two directions.

For the reinforcement of light metals, boron fibers and silicon carbide are used. Carbon fibers have especially valuable properties; they are used to reinforce metal, ceramic and polymer composite materials.

Eutectic composite materials- alloys of eutectic or close to eutectic composition, in which the strengthening phase is oriented crystals formed in the process of directional crystallization. Unlike conventional composite materials, eutectic materials are obtained in one operation. Directional oriented structure can be obtained on already finished products. The shape of the resulting crystals can be in the form of fibers or plates. Directional crystallization methods produce composite materials based on , cobalt, niobium and other elements, so they are used in a wide temperature range.

Introduction

Composite material is a heterogeneous solid material consisting of two or more components, among which reinforcing elements can be distinguished that provide the necessary mechanical characteristics material, and a matrix that provides joint work reinforcing elements. The mechanical behavior of the composite is determined by the ratio of the properties of the reinforcing elements and the matrix, as well as the strength of the bond between them. The efficiency and performance of the material depends on right choice original components and the technology of their combination, designed to provide a strong connection between the components while maintaining their original characteristics. As a result of combining the reinforcing elements and the matrix, a complex of composite properties is formed, which not only reflects the initial characteristics of its components, but also includes properties that isolated components do not possess. In particular, the presence of interfaces between the reinforcing elements and the matrix significantly increases the crack resistance of the material, and in composites, unlike metals, an increase in static strength does not lead to a decrease, but, as a rule, to an increase in fracture toughness characteristics.

Advantages of composite materials:

High specific strength;

High rigidity (modulus of elasticity 130…140 GPa);

High wear resistance;

High fatigue strength;

It is possible to make dimensionally stable structures from CM, and different classes of composites may have one or more advantages.

The most common disadvantages of composite materials:

High price;

Anisotropy of properties;

Increased science intensity of production, the need for special expensive equipment and raw materials, and therefore a developed industrial production and scientific base of the country.

1. Classification of composite materials

Composites are multicomponent materials consisting of a polymer, metal, carbon, ceramic or other base (matrix) reinforced with fillers from fibers, whiskers, fine particles, etc. By selecting the composition and properties of the filler and matrix (binder), their ratio , orientation of the filler, it is possible to obtain materials with the required combination of operational and technological properties. The use of several matrices (polymatrix composite materials) or fillers of various nature (hybrid composite materials) in one material significantly expands the possibilities for controlling the properties of composite materials. Reinforcing fillers perceive the main share of the load of composite materials.

According to the structure of the filler, composite materials are divided into fibrous (reinforced with fibers and whiskers), layered (reinforced with films, plates, layered fillers), dispersion-reinforced, or dispersion-strengthened (with a filler in the form of fine particles). The matrix in composite materials ensures the solidity of the material, the transfer and distribution of stress in the filler, determines the heat, moisture, fire and chemical. durability.

According to the nature of the matrix material, polymer, metal, carbon, ceramic, and other composites are distinguished.

Composite materials with a metal matrix are metal material(usually Al, Mg, Ni and their alloys), reinforced with high-strength fibers (fibrous materials) or finely dispersed refractory particles that do not dissolve in the base metal (dispersion-strengthened materials). The metal matrix binds the fibers (dispersed particles) into a single whole.

Composite materials with a non-metallic matrix have found wide application. As non-metallic matrices, polymer, carbon and ceramic materials. Of the polymer matrices, the most widely used are epoxy, phenol-formaldehyde and polyamide. Carbon matrices, coked or pyrocarbon, are obtained from pyrolyzed synthetic polymers. The matrix binds the composition, giving it form. Strengtheners are fibers: glass, carbon, boron, organic, based on whiskers (oxides, carbides, borides, nitrides, and others), as well as metal (wires), which have high strength and rigidity.

Composite materials with a fibrous filler (reinforcing agent) according to the mechanism of reinforcing action are divided into discrete, in which the ratio of fiber length to diameter is relatively small, and with a continuous fiber. Discrete fibers are randomly arranged in the matrix. The diameter of the fibers is from fractions to hundreds of micrometers. The greater the ratio of length to fiber diameter, the higher the degree of strengthening.

Often a composite material is a layered structure in which each layer is reinforced a large number parallel continuous fibers. Each layer can also be reinforced with continuous fibers woven into a fabric, which is the original shape, corresponding in width and length to the final material. It is not uncommon for fibers to be woven into three-dimensional structures.

Composite materials differ from conventional alloys in more high values temporary resistance and endurance limit (by 50 - 10%), modulus of elasticity, stiffness coefficient and reduced tendency to cracking. The use of composite materials increases the rigidity of the structure while reducing its metal consumption. The strength of composite (fibrous) materials is determined by the properties of the fibers; the matrix should mainly redistribute the stresses between the reinforcing elements. Therefore, the strength and modulus of elasticity of the fibers must be significantly greater than the strength and modulus of elasticity of the matrix. Rigid reinforcing fibers perceive the stresses arising in the composition under loading, give it strength and rigidity in the direction of fiber orientation.

To strengthen aluminum, magnesium and their alloys, boron fibers are used, as well as fibers from refractory compounds (carbides, nitrides, borides and oxides), which have high strength and elastic modulus. To reinforce titanium and its alloys, molybdenum wire, sapphire fibers, silicon carbide and titanium boride are used. An increase in the heat resistance of nickel alloys is achieved by reinforcing them with tungsten or molybdenum wire. Metal fibers are also used in cases where high thermal and electrical conductivity are required. Promising hardeners for high-strength and high-modulus fibrous composite materials are whiskers made of aluminum oxide and nitride, silicon carbide and nitride, boron carbide, etc. Metal-based composite materials have high strength and heat resistance, at the same time they have low plasticity. However, fibers in composite materials reduce the propagation rate of cracks initiating in the matrix, and sudden brittle fracture almost completely disappears. Distinctive feature fibrous uniaxial composite materials are the anisotropy of mechanical properties along and across the fibers and low sensitivity to stress concentrators. The anisotropy of the properties of fibrous composite materials is taken into account when designing parts to optimize properties by matching the resistance field with stress fields. It must be taken into account that the matrix can transfer stresses to the fibers only if there is a strong bond at the interface between the reinforcing fiber and the matrix. To prevent contact between the fibers, the matrix must completely surround all the fibers, which is achieved when its content is not less than 15-20%. The matrix and the fiber should not interact with each other (there should be no mutual diffusion) during manufacture and operation, as this can lead to a decrease in the strength of the composite material. Reinforcement of aluminum, magnesium and titanium alloys with continuous refractory fibers of boron, silicon carbide, titanium boride and aluminum oxide significantly increases the heat resistance. A feature of composite materials is the low rate of softening in time with increasing temperature.

The main disadvantage of composite materials with one and two-dimensional reinforcement is the low resistance to interlaminar shear and transverse shear. Materials with volumetric reinforcement are deprived of this.

In contrast to fibrous composite materials, in dispersion-strengthened composite materials, the matrix is the main load-bearing element, and dispersed particles slow down the movement of dislocations in it.

High strength is achieved with a particle size of 10-500 nm with an average distance between them of 100-500 nm and their uniform distribution in the matrix. Strength and heat resistance, depending on the volume content of hardening phases, do not obey the law of additivity. The optimal content of the second phase for different metals is not the same, but usually does not exceed 5-10 vol. %. The use of stable refractory compounds (thorium, hafnium, yttrium oxides, complex compounds of oxides and rare earth metals) that do not dissolve in the matrix metal as strengthening phases makes it possible to maintain the high strength of the material up to 0.9-0.95 Tm. In this regard, such materials are often used as heat-resistant. Dispersion-strengthened composite materials can be obtained on the basis of most metals and alloys used in engineering. The most widely used alloys based on aluminum - SAP (sintered aluminum powder).

2. Composition, structure and properties of composite materials

The properties of composite materials depend on the composition of the components, their combination, quantitative ratio and bond strength between them. Reinforcing materials can be in the form of fibers, tows, threads, tapes, multilayer fabrics. The content of the hardener in oriented materials is 60-80 vol.%, in non-oriented (with discrete fibers and whiskers) 20-30 vol.%. The higher the strength and modulus of elasticity of the fibers, the higher the strength and stiffness of the composite material. The properties of the matrix determine the strength of the composition in shear and compression and resistance to fatigue failure. In laminated materials, fibers, threads, tapes impregnated with a binder are laid parallel to each other in the laying plane. Flat layers are assembled into plates. The properties are anisotropic. For the work of the material in the product, it is important to consider the direction acting loads. You can create materials with both isotropic and anisotropic properties. It is possible to lay fibers under different angles by varying the properties of composite materials. The bending and torsional stiffness of the material depends on the order of laying the layers along the thickness of the package. The laying of reinforcing elements of three, four or more threads is used. The structure of three mutually perpendicular threads has the greatest application. Hardeners can be located in axial, radial and circumferential directions. Three-dimensional materials can be of any thickness in the form of blocks, cylinders. Bulky fabrics increase peel strength and shear resistance compared to layered fabrics. A system of four strands is built by expanding the reinforcing agent along the diagonals of the cube. The structure of four threads is balanced, has increased shear rigidity in the main planes. However, creating four-directional materials is more difficult than three-directional ones.

Composite materials reinforced with high-strength and high-modulus continuous fibers have received the greatest application in construction and engineering. These include: polymer composite materials based on thermosetting (epoxy, polyester, phenol-formaldehyde, polyamide, etc.) and thermoplastic binders reinforced with glass (fiberglass), carbon (carbon fiber), organic (organoplastic), boron (boroplastic), etc. . fibers; metal composite materials based on Al, Mg, Cu, Ti, Ni, Cr alloys reinforced with boron, carbon or silicon carbide fibers, as well as steel, molybdenum or tungsten wire; composite materials based on carbon reinforced with carbon fibers (carbon-carbon materials); composite materials based on ceramics reinforced with carbon, silicon carbide and other heat-resistant fibers and SiC. When using carbon, glass, amide and boron fibers contained in the material in the amount of 50-70%, compositions with specific strength and modulus of elasticity 2-5 times greater than those of conventional structural materials and alloys were created. In addition, fibrous composite materials are superior to metals and alloys in terms of fatigue strength, heat resistance, vibration resistance, noise absorption, impact strength, and other properties. Thus, the reinforcement of Al alloys with boron fibers significantly improves their mechanical characteristics and makes it possible to increase the operating temperature of the alloy from 250–300 to 450–500 °C. Reinforcement with wire (from W and Mo) and fibers of refractory compounds is used to create heat-resistant composite materials based on Ni, Cr, Co, Ti and their alloys. So, heat-resistant Ni alloys reinforced with fibers can operate at 1300-1350°C. In the manufacture of metallic fibrous composite materials, the application of a metal matrix to a filler is carried out mainly from a melt of the matrix material, by electrochemical deposition or sputtering. The molding of products is carried out by Ch. arr. by impregnating the frame of reinforcing fibers with a metal melt under pressure up to 10 MPa or by combining foil (matrix material) with reinforcing fibers using rolling, pressing, extrusion when heated to the melting temperature of the matrix material.

One of the common technological methods for the manufacture of polymer and metal fibrous and layered composite materials is the growth of filler crystals in a matrix directly in the process of manufacturing parts. This method is used, for example, to create eutectic heat-resistant alloys based on Ni and Co. Alloying of melts with carbide and intermetallic compounds, which form fibrous or lamellar crystals upon cooling under controlled conditions, leads to strengthening of the alloys and makes it possible to increase their operating temperature by 60-80oC. Composite materials based on carbon combine low density with high thermal conductivity, chem. resistance, dimensional stability at sharp temperature changes, as well as with an increase in strength and elasticity modulus when heated to 2000 ° C in an inert medium. High-strength composite materials based on ceramics are obtained by reinforcing with fibrous fillers, as well as metal and ceramic dispersed particles. Reinforcement with continuous SiC fibers makes it possible to obtain composite materials characterized by increased viscosity, flexural strength and high resistance to oxidation at high temperatures. However, the reinforcement of ceramics with fibers does not always lead to a significant increase in its strength properties due to the lack of an elastic state of the material at a high value of its modulus of elasticity. Reinforcement with dispersed metal particles makes it possible to create ceramic-metal materials (cermets) with increased strength, thermal conductivity, and resistance to thermal shocks. In the manufacture of ceramic composite materials, hot pressing, pressing followed by sintering, and slip casting are usually used. Reinforcement of materials with dispersed metal particles leads to a sharp increase in strength due to the creation of barriers to the movement of dislocations. Such reinforcement arr. used in the creation of heat-resistant chromium-nickel alloys. Materials are obtained by introducing fine particles into molten metal, followed by the usual processing of ingots into products. The introduction of, for example, ThO2 or ZrO2 into the alloy makes it possible to obtain dispersion-strengthened heat-resistant alloys that work for a long time under load at 1100-1200°C (the working capacity limit of conventional heat-resistant alloys under the same conditions is 1000-1050°C). A promising direction in the creation of high-strength composite materials is the reinforcement of materials with whiskers, which, due to their small diameter, are practically devoid of defects present in more large crystals and have high strength. Crystals of Al2O3, BeO, SiC, B4C, Si3N4, AlN and graphite with a diameter of 1-30 µm and a length of 0.3-15 mm are of the most practical interest. Such fillers are used in the form of oriented yarn or isotropic laminates like paper, cardboard, felt. The introduction of whiskers into a composition can give it unusual combinations of electrical and magnetic properties. The choice and purpose of composite materials are largely determined by the loading conditions and operating temperature of parts or structures, technol. opportunities. The most accessible and mastered polymer composite materials. A large range of matrices in the form of thermosetting and thermoplastic polymers provides a wide range of composite materials for operation in the range from negative temperatures to 100–200°C for organoplastics, up to 300–400°C for glass, carbon, and boron plastics. Polymer composite materials with polyester and epoxy matrix work up to 120-200°C, with phenol-formaldehyde - up to 200-300 °C, polyimide and organosilicon - up to 250-400°C. Metal composite materials based on Al, Mg and their alloys, reinforced with fibers from B, C, SiC, are used up to 400-500°C; Composite materials based on Ni and Co alloys operate at temperatures up to 1100-1200°C, those based on refractory metals and compounds - up to 1500-1700°C, those based on carbon and ceramics - up to 1700-2000°C. The use of composites as structural, heat-shielding, anti-friction, radio- and electrical, and other materials makes it possible to reduce the weight of the structure, increase the resources and capacities of machines and units, and create fundamentally new components, parts, and structures. All types of composite materials are used in the chemical, textile, mining, metallurgical industries, mechanical engineering, transport, for the manufacture of sports equipment, etc.

3. Economic efficiency application of composite materials

The areas of application of composite materials are not limited. They are used in aviation for highly loaded parts (plating, spars, ribs, panels, compressor and turbine blades, etc.), in space technology for units of power structures of vehicles, for stiffening elements, panels, in the automotive industry to lighten bodies, springs, frames, body panels, bumpers, etc., in the mining industry (drilling tools, combine harvester parts, etc.), in civil engineering (bridge spans, elements of prefabricated structures of high-rise buildings, etc.) and in other areas National economy.

Application composite materials provides a new qualitative leap in increasing the power of engines, power and transport installations, reducing the weight of machines and devices. Composite materials with a non-metallic matrix, namely, polymeric carbon fibers are used in the shipbuilding and automotive industries (racing car bodies, chassis, propellers); bearings, heating panels, sport equipment, computer parts. High-modulus carbon fibers are used for the manufacture of aircraft parts, equipment for the chemical industry, in X-ray equipment, and others. Carbon matrix carbon fibers replace Various types graphites. They are used for thermal protection, aircraft brake discs, chemically resistant equipment. Boron fiber products are used in aviation and space technology (profiles, panels, compressor rotors and blades, propeller blades, helicopter transmission shafts, etc.). Organic fibers are used as insulating and structural material in the electrical and radio industry, aviation technology, etc.

List of used literature

Gorchakov G.I., Bazhenov Yu.M. Construction Materials/ G.I. Gorchakov, Yu.M. Bazhenov. – M.: Stroyizdat, 1986.

Building materials / Under the editorship of V.G. Mikulsky. – M.: ASV, 2000.

General course of building materials / Ed. I.A. Rybyeva. - M .: Higher school, 1987.

Building materials / Under the editorship of G.I. Gorchakov. - M: Higher School, 1982.

Evald V.V. Building materials, their manufacture, properties and testing / V.V. Ewald. - St. Petersburg: L-M, 14th ed., 1933.

1. Composite or composite materials are the materials of the future.

After the modern physics of metals explained to us in detail the reasons for their plasticity, strength and its increase, an intensive systematic development of new materials began. This will lead, probably in the imaginable future, to the creation of materials with a strength many times greater than that of today's conventional alloys. In this case, much attention will be paid to the already known mechanisms of steel hardening and aging of aluminum alloys, combinations of these known mechanisms with forming processes and numerous possibilities for creating combined materials. Two promising avenues are opened up by composite materials reinforced with either fibers or dispersed solids. For the first time, the thinnest high-strength fibers made of glass, carbon, boron, beryllium, steel or whisker single crystals are introduced into an inorganic metal or organic polymer matrix. As a result of this combination, maximum strength is combined with a high modulus of elasticity and low density. Composite materials are such materials of the future.

Composite material - a structural (metallic or non-metallic) material in which there are reinforcing elements in the form of threads, fibers or flakes of more durable material. Examples of composite materials: plastic reinforced with boron, carbon, glass fibers, tows or fabrics based on them; aluminum reinforced with steel filaments, beryllium. Combining the volume content of the components, it is possible to obtain composite materials with the required values of strength, heat resistance, modulus of elasticity, abrasion resistance, as well as to create compositions with the necessary magnetic, dielectric, radio absorbing and other special properties.

2. Types of composite materials.

2.1. Composite materials with a metal matrix.

Composite materials or composite materials consist of a metal matrix (usually Al, Mg, Ni and their alloys) reinforced with high-strength fibers (fibrous materials) or finely dispersed refractory particles that do not dissolve in the base metal (dispersion-strengthened materials). The metal matrix binds the fibers (dispersed particles) into a single whole. Fiber (dispersed particles) plus a binder (matrix) that make up a particular composition are called composite materials.

2.2. Composite materials with non-metallic matrix.

Composite materials with a non-metallic matrix have found wide application. Polymer, carbon and ceramic materials are used as non-metallic matrices. Of the polymer matrices, the most widely used are epoxy, phenol-formaldehyde and polyamide.
Carbon matrices coked or pyrocarbon obtained from synthetic polymers subjected to pyrolysis. The matrix binds the composition, giving it a form. Strengtheners are fibers: glass, carbon, boron, organic, based on whiskers (oxides, carbides, borides, nitrides, and others), as well as metal (wires), which have high strength and rigidity.

The content of the hardener in oriented materials is 60-80 vol. %, in non-oriented (with discrete fibers and whiskers) - 20-30 vol. %. The higher the strength and modulus of elasticity of the fibers, the higher the strength and stiffness of the composite material. The properties of the matrix determine the strength of the composition in shear and compression and resistance to fatigue failure.

According to the type of hardener, composite materials are classified as glass fibers, carbon fibers with carbon fibers, boron fibers and organo fibers.

In laminated materials, fibers, threads, tapes impregnated with a binder are laid parallel to each other in the laying plane. Flat layers are assembled into plates. The properties are anisotropic. For the work of the material in the product, it is important to take into account the direction of the acting loads. You can create materials with both isotropic and anisotropic properties.
You can lay the fibers at different angles, varying the properties of composite materials. The bending and torsional stiffness of the material depends on the order of laying the layers along the thickness of the package.

The laying of reinforcing elements of three, four or more threads is used.
The structure of three mutually perpendicular threads has the greatest application. Hardeners can be located in axial, radial and circumferential directions.

Three-dimensional materials can be of any thickness in the form of blocks, cylinders. Bulky fabrics increase tear strength and shear resistance compared to layered fabrics. A system of four strands is built by expanding the reinforcing agent along the diagonals of the cube. The structure of four threads is balanced, has increased shear rigidity in the main planes.
However, creating four-directional materials is more difficult than three-directional materials.

3. Classification of composite materials.

3.1. Fibrous composite materials.

Often the composite material is a layered structure in which each layer is reinforced with a large number of parallel continuous fibers. Each layer can also be reinforced with continuous fibers woven into a fabric, which is the original shape, corresponding in width and length to the final material. It is not uncommon for fibers to be woven into three-dimensional structures.

Composite materials differ from conventional alloys by higher values of tensile strength and endurance limit (by 50–10%), elasticity modulus, stiffness coefficient, and lower cracking susceptibility. The use of composite materials increases the rigidity of the structure while reducing its metal consumption.

The strength of composite (fibrous) materials is determined by the properties of the fibers; the matrix should mainly redistribute the stresses between the reinforcing elements. Therefore, the strength and modulus of elasticity of the fibers must be significantly greater than the strength and modulus of elasticity of the matrix.
Rigid reinforcing fibers perceive the stresses arising in the composition under loading, give it strength and rigidity in the direction of fiber orientation.

To reinforce titanium and its alloys, molybdenum wire, sapphire fibers, silicon carbide and titanium boride are used.

An increase in the heat resistance of nickel alloys is achieved by reinforcing them with tungsten or molybdenum wire. Metal fibers are also used in cases where high thermal and electrical conductivity are required. Promising hardeners for high-strength and high-modulus fibrous composite materials are whiskers made of aluminum oxide and nitride, silicon carbide and nitride, carbidabor, etc.

Composite materials based on metal have high strength and heat resistance, at the same time they have low plasticity. However, fibers in composite materials reduce the propagation rate of cracks initiating in the matrix, and sudden brittle fracture almost completely disappears. A distinctive feature of fibrous uniaxial composite materials is the anisotropy of mechanical properties along and across the fibers and low sensitivity to stress concentrators.

The anisotropy of the properties of fibrous composite materials is taken into account when designing parts to optimize properties by matching the resistance field with stress fields.

Reinforcement of aluminum, magnesium and titanium alloys with continuous refractory fibers of boron, silicon carbide, titanium doboride and aluminum oxide significantly increases the heat resistance. A feature of composite materials is the low rate of softening in time with increasing temperature.

3.2. Dispersion-strengthened composite materials.

Unlike fibrous composite materials, in dispersion-strengthened composite materials, the matrix is the main load-bearing element, and dispersed particles slow down the movement of dislocations in it.
High strength is achieved with a particle size of 10-500 nm with an average distance between them of 100-500 nm and their uniform distribution in the matrix.
Strength and heat resistance, depending on the volume content of hardening phases, do not obey the law of additivity. The optimal content of the second phase for different metals is not the same, but usually does not exceed 5-10 vol. %.

The use of stable refractory compounds (oxides of thorium, hafnium, yttrium, complex compounds of oxides and rare earth metals) that are insoluble in the matrix metal as strengthening phases allows maintaining the high strength of the material up to 0.9-0.95 T. In connection with this, such materials are often used as heat-resistant. Dispersion-strengthened composite materials can be obtained on the basis of most metals and alloys used in engineering.

The most widely used alloys based on aluminum - SAP (sintered aluminum powder).

The density of these materials is equal to the density of aluminum, they are not inferior to it in corrosion resistance and can even replace titanium and corrosion-resistant steels when operating in the temperature range of 250-500 °C. In terms of long-term strength, they are superior to wrought aluminum alloys. The long-term strength for SAP-1 and SAP-2 alloys at 500°C is 45-55 MPa.

Great prospects for nickel dispersion-strengthened materials.
Nickel-based alloys with 2-3 vol. % thorium dioxide or hafnium dioxide. The matrix of these alloys is usually a solid solution of Ni + 20% Cr, Ni + 15% Mo, Ni + 20% Cr and Mo. Alloys VDU-1 (nickel hardened with thorium dioxide), VDU-2 (nickel hardened with hafnium dioxide) and VD-3 (Ni + 20% Cr matrix hardened with thorium oxide) have received wide application. These alloys have high heat resistance. Dispersion-strengthened composite materials, as well as fibrous ones, are resistant to softening with increasing temperature and holding time at a given temperature.

3.3. Fiberglass.

Fiberglass is a composition consisting of a synthetic resin, which is a binder, and a glass fiber filler. As a filler, continuous or short glass fiber is used. The strength of glass fiber increases sharply with a decrease in its diameter (due to the influence of inhomogeneities and cracks that occur in thick sections). The properties of fiberglass also depend on the content of alkali in its composition; best performance in alkali-free glasses of aluminoborosilicate composition.

Non-oriented glass fibers contain a short fiber as a filler. This allows parts to be pressed. complex shape, with metal fittings. The material is obtained with isotopic strength characteristics much higher than those of press powders and even fibers. Representatives of such a material are glass fibers AG-4V, as well as DSV (metered glass fibers), which are used for the manufacture of power electrical parts, mechanical engineering parts (spools, pump seals, etc.). When using unsaturated polyesters as a binder, PSK premixes (pasty) and prepregs AP and PPM (based on a glass mat) are obtained. Prepregs can be used for large products simple forms(car bodies, boats, instrument cases, etc.).

Oriented fiberglass has a filler in the form of long fibers arranged in oriented separate strands and carefully glued together with a binder. This provides higher strength fiberglass.

Fiberglass can operate at temperatures from -60 to 200 ° C, as well as in tropical conditions, withstand large inertial overloads.
When aging for two years, the aging coefficient K = 0.5-0.7.
ionizing radiation little effect on their mechanical and electrical properties. They are used to produce parts of high strength, with fittings and threads.

3.4. Carbon fibers.

Carbon fibers (carbon plastics) are compositions consisting of a polymer binder (matrix) and reinforcing agents in the form of carbon fibers (carbon fibers).

high energy C-C connections carbon fibers allows them to maintain strength at very high temperatures (in neutral and reducing environments up to 2200 ° C), as well as at low temperatures. Protects fibers from oxidation protective coatings(pyrolytic). Unlike glass fibers, carbon fibers are poorly wetted by a binder.
(low surface energy), so they are etched. This increases the degree of activation of carbon fibers by the content of the carboxyl group on their surface. The interlaminar shear strength of carbon fiber increases by 1.6-2.5 times. Whiskerization of TiO, AlN and SiN whisker crystals is used, which gives an increase in interlayer rigidity by 2 times and strength by 2.8 times. Spatially reinforced structures are used.

The binders are synthetic polymers (polymeric carbon fibers); synthetic polymers subjected to pyrolysis (coked carbon fibers); pyrolytic carbon (pyrocarbon carbon fibers).

Epoxyphenolic carbon fibers KMU-1l, reinforced with carbon tape, and KMU-1u on a tow, viscerized with whisker crystals, can work for a long time at temperatures up to 200 °C.

Carbofibers KMU-3 and KMU-2l are obtained on an epoxyanilino-formaldehyde binder, they can be operated at temperatures up to 100 ° C, they are the most technologically advanced. Carbon fibers KMU-2 and
KMU-2l based on polyimide binder can be used at temperatures up to
300 °C.

Carbon fibers are distinguished by high static and dynamic fatigue resistance, retain this property at normal and very low temperatures (the high thermal conductivity of the fiber prevents self-heating of the material due to internal friction). They are water and chemical resistant. After exposure to X-rays in air, E and E almost do not change.

The thermal conductivity of carbon fiber is 1.5-2 times higher than the thermal conductivity of fiberglass. They have the following electrical properties: = 0.0024-0.0034 Ohm cm (along the fibers); ? \u003d 10 and tg \u003d 0.001 (at a current frequency of 10 Hz).

Carboglass fibers contain, along with carbon glass fibers, which reduces the cost of the material.

3.5. Carbon fiber with carbon matrix.

Coking materials are obtained from conventional polymeric carbon fibers subjected to pyrolysis in an inert or reducing atmosphere. At a temperature of 800-1500 °C, carbonized carbonized ones are formed; at 2500-3000 °C, graphitized carbon fibers are formed. To obtain pyrocarbon materials, the hardener is laid out according to the shape of the product and placed in an oven into which a gaseous hydrocarbon (methane) is passed. Under a certain regime (temperature 1100 °C and residual pressure 2660 Pa), methane decomposes and the resulting pyrolytic carbon is deposited on the fibers of the reinforcing agent, binding them.

The coke formed during the pyrolysis of the binder has a high adhesion strength to carbon fiber. In this regard, the composite material has high mechanical and ablative properties, resistance to thermal shock.

Carbon fiber with a carbon matrix of the KUP-VM type in terms of strength and impact strength is 5-10 times superior to special graphites; when heated in an inert atmosphere and vacuum, it retains strength up to 2200
°C, oxidizes in air at 450 °C and requires a protective coating.
The coefficient of friction of one carbon fiber with a carbon matrix is otherwise high (0.35-0.45), and the wear is low (0.7-1 microns for braking).

3.6. Boron fibers.

Boron fibers are compositions of a polymeric binder and a reinforcing agent - boron fibers.

Boron fibers are distinguished by high compressive strength, shear shear, low creep, high hardness and modulus of elasticity, thermal and electrical conductivity. The cellular microstructure of boron fibers provides high shear strength at the interface with the matrix.

In addition to continuous boron fiber, complex boron glassites are used, in which several parallel boron fibers are braided with glass fiber, which imparts dimensional stability. The use of boron glass makes it easier technological process material manufacturing.

Modified epoxy and polyimide binders are used as matrices for obtaining boron fiber. Boron fibers KMB-1 and
KMB-1k are designed for long work at a temperature of 200 °C; KMB-3 and KMB-3k do not require high pressure during processing and can operate at a temperature not exceeding 100 ° C; KMB-2k is operational at 300 °C.

Boron fibers have high fatigue resistance, they are resistant to radiation, water, organic solvents and combustible materials.

3.7. Organic fibers.

Organic fibers are composite materials consisting of a polymeric binder and reinforcing agents (fillers) in the form of synthetic fibers. Such materials have a low weight, relatively high specific strength and rigidity, and are stable under the action of alternating loads and a sharp change in temperature. For synthetic fibers, the loss of strength during textile processing is small; they are less sensitive to damage.

For organ fibers, the values of the modulus of elasticity and temperature coefficients of linear expansion of the hardener and binder are close.
There is a diffusion of the components of the binder into the fiber and chemical interaction between them. The structure of the material is defect-free. Porosity does not exceed 1-3% (in other materials 10-20%). Hence the stability of the mechanical properties of organo-fibers with a sharp temperature drop, the action of shock and cyclic loads. Impact strength is high (400-700kJ/m²). The disadvantage of these materials is the relatively low compressive strength and high creep (especially for elastic fibers).

Organic fibers are stable in aggressive environments and in a humid tropical climate; dielectric properties are high and thermal conductivity is low. Most organofibers can work for a long time at a temperature of 100-150 °C, and based on a polyimide binder and polyoxadiazole fibers - at a temperature of 200-300 °C.

AT combined materials along with synthetic fibers, mineral fibers are used (glass, carbon fibers and boron fibers). Such materials have greater strength and rigidity.

4. Economic efficiency of the use of composite materials.

The areas of application of composite materials are not limited. They are used in aviation for highly loaded parts of aircraft (skin, spars, ribs, panels, etc.) and engines (compressor blades and turbines, etc.), in space technology for units of load-bearing structures of vehicles subjected to heating, for stiffening elements, panels , in the automotive industry to lighten bodies, springs, frames, body panels, bumpers, etc., in the mining industry (drilling tools, combine harvester parts, etc.), in civil engineering (bridge spans, elements of prefabricated structures of high-rise buildings, etc.). etc.) and in other areas of the national economy.

The use of composite materials provides a new qualitative leap in increasing the power of engines, power and transport installations, reducing the weight of machines and devices.

The technology for obtaining semi-finished products and products from composite materials is well developed.

Composite materials with a non-metallic matrix, namely, polymeric carbon fibers, are used in the shipbuilding and automotive industries (body cars, chassis, propellers); bearings, heating panels, sports equipment, computer parts are made from them. High-modulus carbon fibers are used for the manufacture of aircraft parts, equipment for the chemical industry, in X-ray equipment and others.

Carbon matrix carbon fiber replaces various types of graphite. They are used for thermal protection, aircraft brake discs, chemical resistant equipment.

Products made of boron fibers are used in aviation and space technology (profiles, panels, rotors and compressor blades, propeller blades and transmission shafts of helicopters, etc.).

Organofibers are used as an insulating structural material in the electrical and radio industry, aviation technology, and automotive engineering; pipes, containers for reagents, ship hull coatings and more are made from them.

Announcements for the purchase and sale of equipment can be viewed at

You can discuss the advantages of polymer grades and their properties at

composite material sudlal, composite material impex
Composite material(KM), composite- artificially created inhomogeneous solid material, consisting of two or more components with a clear interface between them. In most composites (with the exception of layered ones), the components can be divided into a matrix (or binder) and reinforcing elements (or fillers) included in it. In composites for structural purposes, reinforcing elements usually provide the necessary mechanical characteristics of the material (strength, rigidity, etc.), and the matrix ensures the joint operation of the reinforcing elements and protects them from mechanical damage and aggressive chemical environments.

The mechanical behavior of the composition is determined by the ratio of the properties of the reinforcing elements and the matrix, as well as the strength of the bonds between them. The characteristics and properties of the created product depend on the choice of initial components and the technology of their combination.

When reinforcing elements and the matrix are combined, a composition is formed that has a set of properties that reflect not only the initial characteristics of its components, but also new properties that individual components do not possess. For example, the presence of interfaces between the reinforcing elements and the matrix significantly increases the crack resistance of the material, and in compositions, unlike homogeneous metals, an increase in static strength does not lead to a decrease, but, as a rule, to an increase in fracture toughness characteristics.

To create a composition, a variety of reinforcing fillers and matrices are used. These are getinax and textolite (laminated plastics made of paper or fabric glued with thermosetting adhesive), glass and graphite plastics (fabric or wound fiber made of glass or graphite, impregnated epoxy adhesives), plywood. There are materials in which a thin fiber made of high-strength alloys is filled with an aluminum mass. Bulat is one of the oldest composite materials. it the thinnest layers (sometimes threads) of high-carbon steel are "glued" with soft low-carbon iron.

Materials scientists are experimenting with the goal of creating more convenient in production, and therefore more cheap materials. Self-growing crystalline structures glued into a single mass with polymer glue (cements with additives of water-soluble adhesives), thermoplastic compositions with short reinforcing fibers, etc. are studied.

1 Classification of composites
2 Benefits of composite materials
3 Disadvantages of composite materials
- 3.1 High cost
- 3.2 Anisotropy of properties
- 3.3 Low impact strength
- 3.4 High specific volume
- 3.5 Hygroscopicity
- 3.6 Toxicity
- 3.7 Poor maintainability
4 Applications
- 4.1 Consumer goods
- 4.2 Sports equipment
- 4.3 Medicine
- 4.4 Mechanical engineering
  - 4.4.1 Characteristic
  - 4.4.2 Specifications
  - 4.4.3 Technical and economic advantages
  - 4.4.4 Applications of technology
- 4.5 Aviation and astronautics
- 4.6 Armament and military equipment
5 See also
6 Notes
7 Literature
8 Links

Composites classification

Composites are usually classified according to the type of reinforcing filler:

fibrous (reinforcing component - fibrous structures);
layered;
filled plastics (reinforcing component - particles)
- bulk (homogeneous),
- skeletal (initial structures filled with a binder).

Also, composites are sometimes classified according to the material of the matrix:

polymer matrix composites,
ceramic matrix composites,
metal matrix composites,
oxide-oxide composites.

Advantages of composite materials

The main advantage of CM is that the material and structure are created simultaneously. The exception is prepregs, which are a semi-finished product for the manufacture of structures.

It should be noted right away that CMs are created for the performance of these tasks, therefore, they cannot contain all the possible advantages, but when designing a new composite, the engineer is free to set him characteristics that are significantly superior to the characteristics of traditional materials when fulfilling this goal in this mechanism, but inferior to them in any other aspects. This means that KM cannot be better. traditional material in everything, that is, for each product, the engineer conducts all necessary calculations and only then chooses the optimum between materials for production.

high specific strength (strength 3500 MPa)
high rigidity (modulus of elasticity 130…140 - 240 GPa)
high wear resistance
high fatigue strength
it is possible to make dimensionally stable structures from CM
ease

Moreover, different classes of composites may have one or more advantages. Some benefits cannot be achieved simultaneously.

Disadvantages of composite materials

Composite materials have enough a large number of shortcomings that hinder their spread.

High price

The high cost of CM is due to the high science intensity of production, the need to use special expensive equipment and raw materials, and, consequently, the developed industrial production and scientific base of the country. However, this is true only when composites replace simple rolled products made of ferrous metals. In the case of light products, products of complex shape, corrosion-resistant products, high-strength dielectric products, composites are the winner. Moreover, the cost of composite products is often lower than analogues made of non-ferrous metals or stainless steel.

Property anisotropy

Anisotropy is the dependence of CM properties on the choice of measurement direction. For example, the modulus of elasticity of unidirectional carbon fiber along the fibers is 10-15 times higher than in the transverse direction.

To compensate for anisotropy, the safety factor is increased, which can neutralize the advantage of CM in specific strength. The experience of using CM in the manufacture of the vertical tail of the MiG-29 fighter can serve as such an example. Due to the anisotropy of the KM used, the vertical tail was designed with a safety factor that is a multiple of the standard factor in aviation of 1.5, which ultimately led to the fact that the composite vertical tail of the MiG-29 turned out to be equal in weight to the design of the classic vertical tail made of duralumin .

However, in many cases, property anisotropy is useful. For example, pipes operating under internal pressure experience twice the breaking stresses in the circumferential direction compared to the axial one. Therefore, the pipe does not have to be of equal strength in all directions. In the case of composites, this condition can be easily ensured by doubling the reinforcement in the circumferential direction compared to the axial one.

Low impact strength

Low impact strength is also the reason for the need to increase the margin of safety. In addition, low impact strength causes high damage to CM products, a high probability of hidden defects, which can only be detected by instrumental methods of control.

High specific volume

High specific volume is significant disadvantage when using CM in areas with severe restrictions on the occupied volume. This applies, for example, to the field of supersonic aviation, where even a slight increase in the volume of an aircraft leads to a significant increase in wave aerodynamic drag.

Hygroscopicity

Composite materials are hygroscopic, that is, they tend to absorb moisture, which is due to the discontinuity of the internal structure of the CM. At long-term operation and repeated temperature transition through 0 Celsius, water penetrating into the structure of the CM destroys the product from the CM from the inside (the effect is similar in nature to the destruction highways during the off-season). In fairness, it should be noted that this drawback refers to the first generation composites, which had insufficient effective adhesion of the binder to the filler, as well as a large volume of cavities in the binder matrix. Modern types composites with high adhesion of the binder to the filler (achieved by the use of special lubricants), obtained by vacuum molding with a minimum amount of residual gas caverns, are not subject to this drawback, which makes it possible, in particular, to build composite ships, produce composite reinforcement and composite supports for overhead power lines.

However, CMs can absorb other highly penetrating liquids, such as aviation kerosene or other petroleum products.

Toxicity

During operation, CMs can emit fumes that are often toxic. If products are made from CM that will be located in close proximity to a person (such an example can be the composite fuselage of the Boeing 787 Dreamliner aircraft), then additional studies of the impact of CM components on humans are required to approve the materials used in the manufacture of CM.

Low maintenance manufacturability

Composite materials may have low operational manufacturability, low maintainability and high cost operation. This is due to the need to use special labor-intensive methods (and sometimes manual labor), special tools for the completion and repair of objects from CM. Often products from KM are not subject to any refinement and repair at all.

Areas of use

Consumer Goods

Reinforced concrete is one of the oldest and simplest composite materials.
Rods for fishing fiberglass and carbon fiber
fiberglass boats
Car tires
Metal composites

Sports equipment

Composites are firmly established in sports: for high achievements high strength and low weight are needed, and the price does not play a special role.

Bicycles
Ski equipment - poles and skis
Hockey sticks and skates
Kayaks, canoes and paddles
Body parts for racing cars and motorcycles
Helmets

The medicine

Material for dental fillings. The plastic matrix serves for good fillability, the glass particle filler increases wear resistance.

mechanical engineering

In mechanical engineering, composite materials are widely used to create protective coatings on friction surfaces, as well as for the manufacture various details engines internal combustion(pistons, connecting rods).

Characteristic

The technology is used to form additional protective coatings on surfaces in steel-rubber friction pairs. The use of technology allows to increase the duty cycle of seals and shafts industrial equipment working in the aquatic environment.

Composite materials are composed of several functionally distinct materials. The basis of inorganic materials is silicates of magnesium, iron, and aluminum modified with various additives. Phase transitions in these materials occur at sufficiently high local loads close to the ultimate strength of the metal. At the same time, a high-strength cermet layer is formed on the surface in the zone of high local loads, due to which it is possible to change the structure of the metal surface.

Polymeric materials based on polytetrafluoroethylenes are modified with ultradispersed diamond-graphite powders obtained from explosive materials, as well as ultrafine powders of soft metals. Plastification of the material is carried out at relatively low (less than 300 °C) temperatures.

Organometallic materials derived from natural fatty acids contain a significant amount of acidic functional groups. Due to this, interaction with surface metal atoms can be carried out in the rest mode. Friction energy accelerates the process and stimulates the appearance of cross-links.

Specifications

The protective coating, depending on the composition of the composite material, can be characterized by the following properties:

thickness up to 100 microns;
shaft surface cleanliness class (up to 9);
have pores with sizes of 1 - 3 microns;
friction coefficient up to 0.01;
high adhesion to the surface of metal and rubber.

Technical and economic advantages

A high-strength cermet layer is formed on the surface in the zone of high local loads;
The layer formed on the surface of polytetrafluoroethylenes has a low coefficient of friction and low resistance to abrasive wear;
Metal-organic coatings are soft, have a low coefficient of friction, porous surface, the thickness of the additional layer is a few microns.

Application areas of the technology

drawing on work surface seals to reduce friction and create a separating layer that prevents rubber from sticking to the shaft during the rest period.
high-speed internal combustion engines for auto and aircraft construction.

Aviation and astronautics

Since the 1960s, there has been an urgent need in aviation and aerospace for the manufacture of strong, lightweight and wear-resistant structures. Composite materials are used for the manufacture of load-bearing structures of aircraft, artificial satellites, heat-insulating coatings for shuttles, and space probes. Increasingly, composites are used for the manufacture of skins for air and spacecraft, and the most loaded power elements.

Armament and military equipment

Due to their characteristics (strength and lightness), CMs are used in military affairs for the production various kinds armor:

body armor (see also kevlar)
armor for military vehicles

Until the 4th century BC e. were widely used as part of bows as weapons.

Notes

J. Lubin. 1.2 Terms and definitions // Handbook of composite materials: 2 books = Handbook of Composites. - M.: Mashinostroenie, 1988. - T. 1. - 448 p. - ISBN 5-217-00225-5.

Literature

Kerber ML, Polymer composite materials. Structure. Properties. Technology. - St. Petersburg: Profession, 2008. - 560 p.
Vasiliev VV, Mechanics of structures made of composite materials. - M.: Mashinostroenie, 1988. - 272 p.
Karpinos D. M., Composite materials. Directory. - Kyiv, Naukova Dumka

Composite Material Information About

1. Composite or composite materials are the materials of the future.

Composite material is a structural (metallic or non-metallic) material in which there are reinforcing elements in the form of threads, fibers or flakes of a more durable material. Examples of composite materials: plastic reinforced with boron, carbon, glass fibers, tows or fabrics based on them; aluminum reinforced with steel filaments, beryllium. Combining the volume content of the components, it is possible to obtain composite materials with the required values of strength, heat resistance, modulus of elasticity, abrasion resistance, as well as to create compositions with the necessary magnetic, dielectric, radio absorbing and other special properties.

2. Types of composite materials.

2.1. Composite materials with a metal matrix.

2.2. Composite materials with non-metallic matrix.

According to the type of hardener, composite materials are classified as glass fibers, carbon fibers with carbon fibers, boron fibers and organo fibers.

3. Classification of composite materials.

3.1. Fibrous composite materials.

To reinforce titanium and its alloys, molybdenum wire, sapphire fibers, silicon carbide and titanium boride are used.

The anisotropy of the properties of fibrous composite materials is taken into account when designing parts to optimize properties by matching the resistance field with stress fields.

3.2. Dispersion-strengthened composite materials.

The most widely used alloys based on aluminum - SAP (sintered aluminum powder).

3.3. Fiberglass.

Fiberglass is a composition consisting of a synthetic resin, which is a binder, and a glass fiber filler. As a filler, continuous or short glass fiber is used. The strength of glass fiber increases sharply with a decrease in its diameter (due to the influence of inhomogeneities and cracks that occur in thick sections). The properties of fiberglass also depend on the content of alkali in its composition; the best performance of alkali-free glasses of aluminoborosilicate composition.

Non-oriented glass fibers contain a short fiber as a filler. This allows you to press parts of complex shape, with metal fittings. The material is obtained with isotopic strength characteristics much higher than those of press powders and even fibers. Representatives of such a material are glass fibers AG-4V, as well as DSV (metered glass fibers), which are used for the manufacture of power electrical parts, mechanical engineering parts (spools, pump seals, etc.). When using unsaturated polyesters as a binder, PSK premixes (pasty) and prepregs AP and PPM (based on a glass mat) are obtained. Prepregs can be used for large-sized products of simple shapes (car bodies, boats, instrument cases, etc.).

Oriented fiberglass has a filler in the form of long fibers arranged in oriented separate strands and carefully glued together with a binder. This provides higher strength fiberglass.

Fiberglass can operate at temperatures from -60 to 200 ° C, as well as in tropical conditions, withstand large inertial overloads.
When aging for two years, the aging coefficient K = 0.5-0.7.
Ionizing radiation has little effect on their mechanical and electrical properties. They are used to produce parts of high strength, with fittings and threads.

3.4. Carbon fibers.

Carbon fibers (carbon plastics) are compositions consisting of a polymer binder (matrix) and reinforcing agents in the form of carbon fibers (carbon fibers).

The high C-C bond energy of carbon fibers allows them to maintain strength at very high temperatures (in neutral and reducing environments up to 2200 ° C), as well as at low temperatures. The fibers are protected from oxidation by protective coatings (pyrolytic). Unlike glass fibers, carbon fibers are poorly wetted by a binder.
(low surface energy), so they are etched. This increases the degree of activation of carbon fibers by the content of the carboxyl group on their surface. The interlaminar shear strength of carbon fiber increases by 1.6-2.5 times. Whiskerization of TiO, AlN and SiN whisker crystals is used, which gives an increase in interlayer rigidity by 2 times and strength by 2.8 times. Spatially reinforced structures are used.

The binders are synthetic polymers (polymeric carbon fibers); synthetic polymers subjected to pyrolysis (coked carbon fibers); pyrolytic carbon (pyrocarbon carbon fibers).

Epoxyphenolic carbon fibers KMU-1l, reinforced with carbon tape, and KMU-1u on a tow, viscerized with whisker crystals, can work for a long time at temperatures up to 200 °C.

Carboglass fibers contain, along with carbon glass fibers, which reduces the cost of the material.

3.5. Carbon fiber with carbon matrix.

3.6. Boron fibers.

Boron fibers are compositions of a polymeric binder and a reinforcing agent - boron fibers.

In addition to continuous boron fiber, complex boron glassites are used, in which several parallel boron fibers are braided with glass fiber, which imparts dimensional stability. The use of boron glass fibers facilitates the technological process of manufacturing the material.

Modified epoxy and polyimide binders are used as matrices for obtaining boron fiber. Boron fibers KMB-1 and
KMB-1k are designed for long-term operation at a temperature of 200 °C; KMB-3 and KMB-3k do not require high pressure during processing and can operate at temperatures not exceeding 100 °C; KMB-2k is operational at 300 °C.

Boron fibers have high fatigue resistance, they are resistant to radiation, water, organic solvents and fuels and lubricants.

3.7. Organic fibers.

In combined materials, along with synthetic fibers, mineral fibers are used (glass, carbon fibers and boron fibers). Such materials have greater strength and rigidity.

4. Economic efficiency of the use of composite materials.

The use of composite materials provides a new qualitative leap in increasing the power of engines, power and transport installations, reducing the weight of machines and devices.

The technology for obtaining semi-finished products and products from composite materials is well developed.

Carbon matrix carbon fiber replaces various types of graphite. They are used for thermal protection, aircraft brake discs, chemical resistant equipment.

Products made of boron fibers are used in aviation and space technology (profiles, panels, rotors and compressor blades, propeller blades and transmission shafts of helicopters, etc.).

Announcements for the purchase and sale of equipment can be viewed at

You can discuss the advantages of polymer grades and their properties at

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The use of composite materials. Obtaining polymer composite materials

Classification of composite materials

1. Composite or composite materials are the materials of the future.

2. Types of composite materials.

3. Classification of composite materials.

4. Economic efficiency of the use of composite materials.

Composites classification

Advantages of composite materials

Disadvantages of composite materials

High price

Property anisotropy

Low impact strength

High specific volume

Hygroscopicity

Toxicity

Low maintenance manufacturability

Areas of use

Consumer Goods

Sports equipment

The medicine

mechanical engineering

Characteristic

Specifications

Technical and economic advantages

Application areas of the technology

Aviation and astronautics

Armament and military equipment

see also

Notes

Literature

Links

Composite Material Information About

1. Composite or composite materials are the materials of the future.

2. Types of composite materials.

3. Classification of composite materials.

4. Economic efficiency of the use of composite materials.

What else to read

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