Natural composite materials. Technologies for the production of composite materials

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

After modern physics of metals explained to us in detail the reasons for their plasticity, strength and its increase, intensive systematic development of new materials began. This will probably lead, already in the imaginable future, to the creation of materials with strength much greater than that of conventional alloys today. 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 formation processes and numerous possibilities for creating combined materials. Combined materials reinforced with either fibers or dispersed solid particles offer two promising paths. The first to introduce the finest high-strength fibers of glass, carbon, boron, beryllium, steel or thread-like single crystals into an inorganic metal or organic polymer matrix. As a result of this combination, maximum strength is combined with a high elastic modulus and low density. These are the materials of the future composite materials.

Composite material is a structural (metallic or non-metallic) material that contains reinforcing elements in the form of threads, fibers or flakes of a stronger material. Examples of composite materials: plastic reinforced with boron, carbon, glass fibers, strands or fabrics based on them; aluminum reinforced with steel and beryllium threads. By combining the volumetric content of components, it is possible to obtain composite materials with the required values of strength, heat resistance, elastic modulus, abrasive resistance, as well as 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), strengthened 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 one or another composition are called composite materials.

2.2. Composite materials with a 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. The most widely used polymer matrices are epoxy, phenol-formaldehyde and polyamide.
Coked or pyrocarbon carbon matrices are obtained from synthetic polymers subjected to pyrolysis. The matrix binds the composition, giving it shape. Strengtheners are fibers: glass, carbon, boron, organic, based on whisker crystals (oxides, carbides, borides, nitrides and others), as well as metal (wires), which have high strength and rigidity.

The properties of composite materials depend on the composition of the components, their combination, quantitative ratio and strength of bond between them.
Reinforcing materials can be in the form of fibers, strands, threads, tapes, multilayer fabrics.

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

Based on the type of reinforcement, composite materials are classified as glass fibers, carbon fibers with carbon fibers, boron fibers and organofibers.

In layered 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 material to work in a product, it is important to take into account the direction of the acting loads. It is possible to create materials with both isotropic and anisotropic properties.
You can lay the fibers at different angles, varying the properties of the composite materials. The flexural and torsional rigidities of the material depend on the order in which the layers are laid across the thickness of the package.

Reinforcers of three, four or more threads are used.
Nai greater application has a structure of three mutually perpendicular threads. Reinforcers can be located in the axial, radial and circumferential directions.

Three-dimensional materials can be of any thickness in the form of blocks or cylinders. Bulky fabrics increase peel strength and shear resistance compared to laminated fabrics. A system of four threads is constructed by decomposing the reinforcement along the diagonals of the cube. The structure of four threads is equilibrium and has increased shear rigidity in the main planes.
However, creating four-directional materials is more difficult than creating three-directional materials.

3. Classification of composite materials.

3.1. Fiber 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 that is the original shape, the width and length corresponding to the final material. Often the fibers are woven into three-dimensional structures.

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

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

To strengthen aluminum, magnesium and their alloys, boron, as well as fibers from refractory compounds (carbides, nitrides, borides and oxides) having high strength and elasticity modulus, are used. Wire made from high-strength steels is often used as fibers.

For the reinforcement of titanium and its alloys, molybdenum wire, sapphire fibers, silicon carbide and titanium boride are used.

Increasing 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 strengtheners 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, while at the same time they have low plasticity. However, fibers in composite materials reduce the rate of propagation of cracks initiated in the matrix, and sudden brittle failure almost completely disappears. Distinctive feature Fibrous uniaxial composite materials are characterized by anisotropy of mechanical properties along and across the fibers and low sensitivity to stress concentrators.

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

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

The main disadvantage of composite materials with one- and two-dimensional reinforcement is the low resistance to interlayer shear and transverse breakage. Materials with volumetric reinforcement do not have this.

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 inhibit 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 volumetric content of strengthening phases, do not obey the law of additivity. The optimal content of the second phase varies for different metals, 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 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 technology.

The most widely used aluminum-based alloys are 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. Long-term strength for alloys SAP-1 and SAP-2 at 500 °C is 45-55 MPa.

Nickel dispersion-strengthened materials have great prospects.
Nickel-based alloys with 2-3 vol. have the highest heat resistance. % 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. The alloys VDU-1 (nickel strengthened with thorium dioxide), VDU-2 (nickel strengthened with hafnium dioxide) and VD-3 (Ni + 20% Cr matrix, strengthened with thorium oxide) are widely used. These alloys have high heat resistance. Dispersion-strengthened composite materials, just like fibrous ones, are resistant to softening with increasing temperature and duration of exposure at a given temperature.

3.3. Fiberglass.

Fiberglass is a composition consisting of a synthetic resin, which is a binder, and glass fiber filler. Continuous or short glass fiber is used as filler. The strength of fiberglass 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 alkali content in its composition; The best performance is found in alkali-free glasses of aluminoborosilicate composition.

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

Oriented glass fibers have a filler in the form of long fibers, arranged in oriented individual strands and carefully glued together with a binder. This ensures higher strength of 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 high-strength parts with reinforcement and threads.

3.4. Carbon fibers.

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

High Energy S-S 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. The fiber surface is 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. At the same time, the degree of activation of carbon fibers in terms of the content of the carboxyl group on their surface increases. The interlayer shear strength of carbon fiber reinforced plastics increases by 1.6-2.5 times. Viscerization of TiO, AlN and SiN filamentary crystals is used, which results in an increase in interlayer rigidity by 2 times and strength by 2.8 times. Spatially reinforced structures are used.

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

Epoxyphenol carbon fiber reinforced KMU-1l, reinforced with carbon tape, and KMU-1u on a rope, viskerized with whiskers, can operate for a long time at temperatures up to 200 °C.

Carbon fiber fibers KMU-3 and KMU-2l are produced using an epoxyaniline-formaldehyde binder; they can be used at temperatures up to 100 °C; they are the most technologically advanced. Carbon fibers KMU-2 and
KMU-2l based on a polyimide binder can be used at temperatures up to
300 °C.

Carbon fibers are distinguished by high statistical and dynamic fatigue resistance and 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 air, X-rays and E almost do not change.

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

Carbon fiberglass contains glass fibers along with carbon, which reduces the cost of the material.

3.5. Carbon fiber with carbon matrix.

Coked materials are produced from conventional polymer carbon fibers subjected to pyrolysis in an inert or reducing atmosphere. At a temperature of 800-1500 °C, 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 a furnace into which 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 reinforcement fibers, binding them.

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

Carbon fiber with a carbon matrix of the KUP-VM type is 5-10 times higher in strength and impact strength than 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 composite with a carbon matrix is high (0.35-0.45), and wear is low (0.7-1 microns for braking).

3.6. Boron fibers.

Boron fibers are compositions of a polymer binder and strengthener – boron fibers.

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

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

Modified epoxy and polyimide binders are used as matrices for producing boron fiber nitrates. 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 and are resistant to radiation, water, organic solvents and lubricants.

3.7. Organofibers.

Organofibers are composite materials consisting of a polymer binder and reinforcers (fillers) in the form of synthetic fibers. Such materials have low mass, relatively high specific strength and rigidity, and are stable under the action of alternating loads and sudden changes in temperature. For synthetic fibers, the loss of strength during textile processing is small; They are insensitive to damage.

For organofibers, the values of the elastic modulus and temperature coefficients of linear expansion of the strengthener and binder are close.
Diffusion of binder components into the fiber and chemical interaction between them occurs. 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 organofibers under sharp temperature changes, impact and cyclic loads. Impact strength is high (400-700 kJ/m²). The disadvantage of these materials is their relatively low compressive strength and high creep (especially for elastic fibers).

Organic fibers are resistant to aggressive environments and humid tropical climates; dielectric properties are high and thermal conductivity is low. Most organ fibers can operate for a long time at a temperature of 100-150 °C, and those based on a polyimide binder and polyoxadiazole fibers - at a temperature of 200-300 °C.

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

4. Economic efficiency of using 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 components of power structures of devices subject to heating, for stiffeners, panels , in the automotive industry to lighten bodies, springs, frames, body panels, bumpers, etc., in the mining industry (drilling tools, parts for combines, 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, energy and transport installations, and reducing the weight of machines and devices.

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

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

Carbon fibers with a carbon matrix replace various types of graphite. They are used for thermal protection, aircraft brake discs, and chemically resistant equipment.

Products made from boron fiber are used in aviation and space technology (profiles, panels, compressor rotors and blades, propeller blades and helicopter transmission shafts, etc.).

Organofibers are used as an insulating and structural material in the electrical and radio industry, aviation technology, and automotive industry; They are used to make pipes, containers for reagents, coatings for ship hulls, and more.

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Composite materials, or, as they are commonly called, composites, have revolutionized many industries and have become popular in high-tech products that must be lightweight but at the same time highly resistant to mechanical stress. The expected economic benefits in high-tech projects such as developments in the field of military and space technology are associated primarily with lightweight, high-temperature resistant composite materials, which reduce the weight of the final products, operating costs and fuel consumption.

Modern aviation, both military and civil, would be significantly less efficient without composite materials. In fact, the requirements of this particular industry for materials (which, on the one hand, must be light, and on the other hand, sufficiently strong) were the main guiding force in their development and development. It is now generally accepted that aircraft wings, tails, propellers, and engine turbine blades are made of modern composite materials. The same applies to most of their internal structure and fuselage parts. Cases of some small aircraft already made entirely of composite materials. Large commercial aircraft typically use these materials for their wings, tails, and body panels.

Composite connectors for internal connections, supplied to the market in accordance with its needs and consumer requirements, successfully replace previous connectors that were made of brass, nickel, aluminum, bronze or of stainless steel. Composite connectors are ideal for use in environments environment, where resistance to high temperatures and compliance with electromagnetic compatibility requirements are required. When used, there is virtually no release of toxic gaseous products and, in particular, and most importantly, halogens. Composite materials are stronger than steel, they provide high corrosion resistance, and have more high reliability and durability, and at the same time they also have significantly less weight than their steel counterparts.

Production of composite materials

Composites are made up of several individual materials. The goal of creating a composite material is to create some new substance that combines the properties of its constituent parts in the most advantageous way. Composite materials have two components: a matrix (binder) and reinforcing elements (fillers).

To create a composite material, at least one component of each type is required. For the matrix, most modern composite materials use thermoplastic or thermoset plastics (also called resins). Plastics are polymers that hold together reinforcing elements, and they help define the desired physical properties final product.

Thermoplastic plastics are characterized by the fact that they are hard at low temperatures but soften when heated. Although they are used less frequently than thermoset plastics, they do have some advantages, such as higher fracture toughness, longer shelf life as raw materials, and recyclability. Using thermoplastic plastics is safer and less polluting workplace, because when preparing them for direct use there is no need for organic solvents to harden them.

Series Deutsch ACT represents high performance composite connectors, made in accordance with the standard MIL-DTL-38999.

The performance of any connector depends on the performance of its component parts. The use of composite materials in the ACT series increased the strength of the connector body and thread locking mechanism, resulting in the number of possible mating cycles reaching 1500. The use of composite materials also increased the corrosion resistance of the connectors (2000 hours in salt spray conditions). In addition, this series of connectors are designed with locking latches, which have a beneficial effect on performance and durability. life cycle connector.

Thermosetting plastics, or thermoset plastics, in their original form are in a liquid state, but harden and become solid (vulcanize) after they are heated. The hardening process is irreversible, so these materials no longer become soft when exposed to high temperatures. When the plastic matrix is reinforced with glass fibers, for example, thermosets successfully resist wear and tear and are highly durable even in harsh environments. Such materials provide both design flexibility and high electrical strength.

If we classify composites according to the matrix material, we distinguish: thermoset composites, composites using short (chopped) fibers and thermosets with long fibers or reinforced with fibers. The most well-known materials for such matrices are polyesters (polyester), epoxy resins, phenol-formaldehydes, polyimides, polyamides and polypropylene. Ceramics, carbon and metals are also used as matrices for some very specific applications. For example, ceramics are used when the material is exposed to very high temperatures, and carbon is used for products that are subject to friction and wear.

Polymers Not only are they used as a matrix material, they are also used as well-proven reinforcing materials to strengthen composites. For example, Kevlar is a polymer fiber that is very strong and adds stiffness combined with toughness to the composite material. Although glass fibers are the most commonly used reinforcement option, composites can also use metal reinforcement in the form of rebar to reinforce other metals, such as in metal matrix composites (MMC). Compared to polymer matrix composites, MMCs are more resistant to ignition and can operate over a wider temperature range, are non-hygroscopic, have higher electrical conductivity and thermal conductivity, are resistant to radiation exposure and do not emit toxic gases. However, they tend to be more expensive than the counterparts they replace and are used where their higher specifications and properties may justify the increased cost.

Today these materials Most often they are used in aircraft components and space systems.

Durability and resistance to elevated temperatures– the most important characteristics in polymers used for high-tech applications. Products intended for commercial and military space applications must be manufactured using so-called engineering plastics or other specialized high-temperature polymers. Engineering plastics such as polyetherimide (PEI), polyphthalamide (PPA), polyphenylene sulfide (PPS) and polyesterimide (PAI) are designed and intended specifically for use at elevated operating temperatures. Resins such as polyetheretherketone (PEEK) and various liquid crystal polymers (LCPs) can also withstand extremely high temperatures. These modern high-tech plastics also meet toxic emissions requirements and are flame resistant.

Advantages of using composite materials

We depend on composite materials for many aspects of our Everyday life. Fiberglass-based composite materials were developed back in the late 40s of the last century; they are the first modern composite materials and are still widely used today. In the total volume of composite materials currently produced, fiberglass-based materials occupy approximately 65%. You may be using products made from fiberglass composite material without even realizing it.

The ever-increasing number of manufacturers of composite materials and the growth of their offerings on the market allows consumers to choose required material taking into account a number of their advantages, such as:

Composites are incredibly lightweight and are therefore increasingly used in internal connection systems (connectors) where low weight is a factor. For most of these applications, the typical weight savings when using composites compared to aluminum is approximately 40%, and 80% compared to brass and stainless steel parts.
Composite materials are extremely durable. As an example, high-strength fiber-structured composites are widely used in body armor. Thanks to the high strength of such composite materials, soldiers are well protected from shrapnel and bullets.
Composites are very resistant to aggressive chemicals and will never rust or corrode. This is precisely why the maritime industry was one of the first to adopt them for use.
Polymer plastics are less susceptible to mechanical resonance, so parts with threaded connections made from these materials are less likely to loosen and unscrew when exposed to shock and strong vibration.
Some composites are not electrically conductive. This is important because composite materials are often needed where strength and high electrical insulating properties are needed.
Composites can attenuate magnetic fields, reduce the effect of magnetic fields on corrosion and dampen the so-called “acoustic signature”, that is, the acoustic radiation characteristic of each device, which is a very important property when developing products for which a low probability of detection is important.

Parts made of composites will fracture under stress with a much lower degree of probability than parts made of metal. A small crack in a metal part can develop into a catastrophic one very quickly and with very serious consequences. Fibrous materials in their complex composite structure can distribute internal stress and block the expansion of small cracks.

The load in any composite is distributed throughout its fibers, it is the fibers that carry all the load, so their type, number, orientation and linearity determine their effectiveness. Fiberglass composites are used for applications that simultaneously require stiffness, high electrical insulation properties, and abrasion resistance. Carbon fibers in composite materials are used for applications requiring high strength and stiffness. The resin matrix in the composite, distributed between the fibers, protects them and keeps the fibers in their correct location and orientation. The type of matrix resin determines its absorption properties, both to water (hygroscopicity) and to chemical compounds, mechanical properties at high temperatures, compressive strength and mechanical rigidity.

In addition, the type of resin determines the manufacturing method of the final product and its cost relative to alternative resin types and manufacturing methods.

Use of composites in the defense and aviation industries

The most important of all the advantages of composite materials is their strength and rigidity, combined with low specific gravity. The most difficult parts to construct are complex composite parts that take advantage of these properties, but must still meet the necessary requirements for geometric dimensions, installation and functional use. But by selecting the appropriate combination of reinforcing material and matrix material, manufacturers can ensure that the product has all the necessary characteristics that will meet the requirements for both its specific design and the specific purpose of its use.

Electrical connectors that provide power and data transmission in military and aerospace products are constantly becoming smaller and lighter. Many military customers are looking for smaller, lighter and more flexible solutions that meet stringent industrial requirements for strength and durability. Recent Developments in the Field constructive solutions and materials have made it possible to make a leap in the technology of production and execution of connectors, which ensure both their high technical characteristics and the necessary requirements for environmental protection.

Composites are the basis of many modern projects in the field of development of devices with minimally noticeable effects. One of them is unmanned aerial vehicles (UAVs). Composite materials were very actively used in their design, resulting in the possibility of their detection only at close range.

Composites provide high durability and stiffness, making them suitable materials for systems used in avionics.

These materials offer reduced weight, high strength and durability that far exceed those of many metals and non-composite thermosets.

The special state of the environment in space requires special components that can be used in outer space conditions; in addition, they must meet the requirements for the absence of toxic gas emissions and be made of non-magnetic materials. Carbon-based composites are the main material in modern launch vehicles and heat shields of reusable spacecraft. They are also widely used in antenna reflectors, spacecraft traverses, payload bay adapters, interconnect structures, and reusable spacecraft heat shields.

It is an undeniable fact that composite materials are increasingly being developed to meet the specific requirements of internal connection systems; despite the increasing complexity of both their design and the manufacturing process, these materials, due to their properties, are worth using. The stumbling block when using composites is usually their cost. Although the manufacturing processes themselves, when composite materials are used, are often more efficient, the raw materials themselves are expensive. Of course, composites will never be able to completely replace traditional materials, such as steel, but the significant advantages of composites provide real cost savings, reducing fuel consumption and saving on system maintenance as a whole, increasing the service life for a large number of defense and space products. Without a doubt, we should be aware of all the possibilities that composites can give us.

Based on materials from the website www.connectorsupplier.com
Jenny Bieksha, Bishop & Associates Inc.
Translation: Vladimir Rentyuk
The article was published in the journal “Bulletin of Electronics” No. 1 2014

Composite materials

Composite material (composite, KM) - a heterogeneous solid material consisting of two or more components, among which we can distinguish reinforcing elements that provide the necessary mechanical characteristics of the material, and a matrix (or binder) that ensures the joint operation of the reinforcing elements.

The mechanical behavior of a composite is determined by the relationship between the properties of the reinforcing elements and the matrix, as well as the strength of the bond between them. The effectiveness and performance of the material depend on the right choice the original components and the technology of their combination, designed to ensure a strong connection between the components while maintaining their original characteristics.

As a result of the combination of reinforcing elements and the matrix, a complex of properties of the composite is formed, which not only reflects the initial characteristics of its components, but also includes properties that the 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

It is worth immediately stipulating that CMs are created to perform these tasks, and accordingly cannot contain all possible advantages, but when designing a new composite, the engineer is free to give it characteristics significantly superior to the characteristics of traditional materials when fulfilling a given purpose in a given mechanism, but inferior to them in any other aspects. This means that CM cannot be better than traditional material in everything, that is, for each product the engineer carries out all the necessary calculations and only then chooses the optimum between materials for production.

high specific strength
high rigidity (elastic modulus 130…140 GPa)
high wear resistance
high fatigue strength
It is possible to manufacture dimensionally stable structures from CM

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

Disadvantages of composite materials

Most classes of composites (but not all) have disadvantages:

high price
anisotropy of properties
increased knowledge intensity of production, the need for special expensive equipment and raw materials, and therefore developed industrial production and scientific base of the country

Areas of use

Consumer goods

Mechanical engineering

Characteristic

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

Composite materials consist of several functional excellent materials. The basis of inorganic materials is magnesium, iron, and aluminum silicates modified with various additives. Phase transitions in these materials occur at fairly high local loads, close to the ultimate strength of the metal. In this case, a high-strength metal-ceramic layer is formed on the surface in an area of high local loads, due to which it is possible to change the structure of the metal surface.

Specifications

Depending on the composition of the composite material, the protective coating 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 metal and rubber surfaces.

Technical and economic advantages

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

Areas of application of technology

application to work surface seals in order to reduce friction and create a separating layer that prevents rubber from sticking to the shaft during the rest period.
high speed engines internal combustion for automobile and aircraft manufacturing.

Aviation and astronautics

Weapons and military equipment

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

armor for military equipment

Classification of composites

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).

Composites are also sometimes classified according to the matrix material:

composites with a polymer matrix,
composites with ceramic matrix,
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 semi-finished products for the manufacture of structures.

It is worth immediately stipulating that CMs are created to perform these tasks, and accordingly cannot contain all possible advantages, but when designing a new composite, the engineer is free to give it characteristics that are significantly superior to the characteristics of traditional materials when fulfilling a given purpose in a given mechanism, but inferior to them in any other aspects. This means that CM cannot be better than traditional material in everything, that is, for each product the engineer carries out all the necessary calculations and only then chooses the optimum between materials for production.

high specific strength (strength 3500 MPa)
high rigidity (elastic modulus 130…140 - 240 GPa)
high wear resistance
high fatigue strength
It is possible to manufacture 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 a fairly large number of disadvantages that hinder their spread.

High price

The high cost of CM is due to the high knowledge intensity of production, the need to use special expensive equipment and raw materials, and therefore the developed industrial production and scientific base of the country. However, this is only true when replacing simple rolled products made of ferrous metals with composites. In the case of lightweight products, products of complex shapes, 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.

Anisotropy of properties

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 offset the advantage of CM in specific strength. An example of this is the experience of using CM in the manufacture of the vertical tail of the MiG-29 fighter. Due to the anisotropy of the used CM, the vertical tail was designed with a safety factor that was a multiple of the standard aviation coefficient 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 structure 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 stress in the circumferential direction compared to the axial direction. Therefore, the pipe should not be of equal strength in all directions. In the case of composites, this condition can be easily achieved by doubling the reinforcement in the circumferential direction compared to the axial one.

Low impact strength

Low impact strength also causes the need to increase the safety factor. In addition, low impact strength causes high damage to CM products and a high probability of hidden defects that can only be detected by instrumental testing methods.

High specific volume

High specific volume is significant drawback when using CM in areas with strict restrictions on the occupied volume. This applies, for example, to the field of supersonic aviation, where even a slight increase in the volume of the 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. During long-term operation and repeated temperature transitions through 0 Celsius, water penetrating into the structure of the CM destroys the CM product from the inside (the effect is similar in nature to the destruction of highways in the off-season). To be fair, it should be noted that this drawback applies to the first generation of composites, which had insufficiently 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 methods with a minimum amount of residual gas cavities, 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, CM can absorb other liquids with high penetrating ability, for example, aviation kerosene or other petroleum products.

Toxicity

During operation, CMs can emit fumes that are often toxic. If CM is used to make products that will be located in close proximity to humans (the composite fuselage of the Boeing 787 Dreamliner may serve as such an example), then additional research into the effects of CM components on humans is required to approve the materials used in the manufacture of CM.

Low operational efficiency

Composite materials may have low manufacturability, low maintainability and high operating costs. This is due to the need to use special labor-intensive methods (and sometimes manual labor), special tools for the modification and repair of objects made of CM. Often products made from CM are not subject to any modification or repair at all.

Areas of use

Consumer goods

Reinforced concrete is one of the oldest and simplest composite materials
Fishing rods made of fiberglass and carbon fiber
Fiberglass boats
Car tires
Metal composites

Sport equipment

Composites have firmly established themselves in sports: high achievements require high strength and low weight, and price does not play a special role.

Bicycles
Equipment for skiing- poles and skis
Hockey sticks and skates
Kayaks, canoes and oars for them
Body parts for racing cars and motorcycles
Helmets

Medicine

Material for dental fillings. The plastic matrix serves for good filling, and 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 of various parts of internal combustion engines (pistons, connecting rods).

Characteristic

Composite materials are composed of several functionally distinct materials. The basis of inorganic materials is magnesium, iron, and aluminum silicates modified with various additives. Phase transitions in these materials occur at fairly high local loads, close to the ultimate strength of the metal. In this case, a high-strength metal-ceramic layer is formed on the surface in an area of high local loads, due to which it is possible to change the structure of the metal surface.

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

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

Specifications

Depending on the composition of the composite material, the protective coating 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 metal and rubber surfaces.

Technical and economic advantages

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

Areas of application of technology

applying seals to the working surface in order 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 automobile and aircraft construction.

Aviation and astronautics

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

Weapons and military equipment

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

body armor (see also Kevlar)
armor for military equipment

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

Notes

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

Literature

Kerber M. L., Polymer composite materials. Structure. Properties. Technologies. - St. Petersburg: Profession, 2008. - 560 p.
Vasiliev V.V., Mechanics of structures made of composite materials. - M.: Mechanical Engineering, 1988. - 272 p.
Karpinos D.M., Composite materials. Directory. - Kyiv, Naukova Duma

Composite Material Information About

During this method, pre-prepared fillers are used. Thanks to this method, high homogeneity of the product is guaranteed for strength, and indicators are controlled. However, the quality of the resulting product depends to a large extent on the skill and experience of the workers.

The production of hand-molded fiberglass products is divided into several stages. The first stage is called preparatory, during which the surface of the matrix of the expected product is cleaned, then degreased and finally a layer of release wax is applied. At the end of the first stage, the matrix is covered with a protective and decorative layer - gelcoat. Thanks to this layer, the outer surface of the future product is formed, the color is set and protection is provided from harmful factors such as water, ultraviolet radiation and chemical reagents. Negative matrices are mainly used to produce the finished product. After the special gelcoat layer has dried, you can move on to the next stage, which is called molding. During this stage, initially cut glass material is placed into the matrix; another type of filler can also be used. Next comes the process of forming the “skeleton” of the expected product. Then the resin with the catalyst, pre-mixed, is applied to the prepared glass material. The resin must be evenly distributed using brushes and soft rollers throughout the matrix. The last stage can be called rolling. It is used to remove air bubbles from a laminate that has not yet hardened. If they are not removed, this will affect the quality of the finished product, so the laminate must be rolled with a hard roller. Once the finished product has hardened, it is removed from the mold and subjected to machining, which includes drilling holes, trimming excess fiberglass around the edges, etc.

Advantages of this method:

there is a real opportunity to obtain a product of complex shape and considerable size with minimal investment;
the design of the product can be easily changed, since embedded parts and fittings are introduced into the product, and the price of the equipment and the required equipment is quite low;
To make the matrix, any material is used that is able to maintain its proportions and shape.

Disadvantages of this method:

significant manual labor costs;
productivity is quite low;
the quality of the product will depend on the qualifications of the molder;
This method is suitable for producing small-scale products.

2. Spraying.

This method is suitable for small and medium-scale production. The spraying method has many advantages over contact molding, even though there are some costs involved in purchasing equipment for this method.

A special installation allows you to apply protective covering and plastic. Due to this, there is no need for preliminary cutting of the material and preparation of the binder, as a result of which the part of manual labor is sharply reduced. Special installations automatically accurately count the doses of resin and hardener, and they also cut the roving into pieces required sizes(0.8 - 5 cm). After the cutting process, parts of the thread must fall into the binder stream and become saturated during transfer to the matrix. Through manual labor, the compaction process for fiberglass in the matrix is carried out using a rolling roller.

A number of advantages in the production of fiberglass by spraying:

time and useful space are saved due to the fact that there is no need to cut the material and prepare the binder;
it is possible to reduce the number of production areas by reducing the number of specially prepared places for molding;
the product molding speed increases;
control over product quality is simplified;
the wage fund is significantly saved;
Due to the fact that roving is a relatively inexpensive material, the cost of the resulting product is significantly reduced.

When the binder is prepared in small quantities, then during manual molding up to 5% of the binder remains on the tools and walls of the container, which is quite uneconomical. It is known that the quality of the resulting product will depend on the skill and experience of the installation operator. This method uses the same tooling as during hand molding.

3. Pultrusion.

Pultrusion technology is based on the continuous production of uniaxially oriented profile products from fibrous plastics. A profile product with a constant cross-section from a suitable material can be obtained by pultrusion.

Thanks to a special pultrusion machine, a fiberglass profile is produced. Such a machine consists of a section for supplying reinforcing materials, a die, a section for impregnation, a pulling unit, and a control unit heating elements and from the trimming section. It is better to strengthen the oriented fiber package in a dry state and impregnate it with a polymer composition pumped through the dry package. Thanks to this technology, air will not get into the material. Excess resin will flow back into the pan and be recycled. Roving, which is used as a reinforcing material, is unwound from reels in a dry state and collected into a bundle in a special way. Then the material enters the impregnation device - this is a special bath with resin, where it is completely wetted with polyester, epoxy or other binder. Then the already impregnated material is sent to a heated die, the task of which is to form the profile configuration. Then the composition hardens at the specified temperature. The result was a fiberglass profile, the configuration of which follows the shape of the die.

It has been proven that products produced by pultrusion have superior properties to parts made by classical molding methods. The increase in cost of this method is due to a number of advantages that are characteristic of this process. Benefits include strict control of fiber tension and directionality, reduced pores, and maintaining a constant fiber content in the composite. It is obvious that even the interlayer shear property is clearly improved. At the moment, several variants of the main pultrusion process have been developed, which are of interest to many and mean a lot to the industry. Their advantages are good electrical, physical, chemical and thermal properties, high performance and excellent dimensional tolerance. One of these pultrusion methods is precisely intended for the production of permanent plate and sheet semi-finished products.

However, each method has its drawbacks. This method is characterized by such a disadvantage as the speed of the process, which will depend on the temperature and rate of hardening of the binder. It is usually small for low heat resistant polyester resins. Another disadvantage is that it is difficult to provide a constant cross-section of the product along its length, with the exception of products with a not particularly complex cross-sectional shape - square, round, I-beam and others. To obtain the product, you must use only threads or strands. However, recently these disadvantages of the method for producing profile products have been gradually eliminated and the use of this process has expanded noticeably. A composition that is based on polyvinyl ethers and epoxy resins are used as polymer matrices. The use of such polymer matrices based on polysulfone, polyethersulfone and plasticized polyimide makes it possible to achieve a molding speed of rods with a diameter of about five mm at a speed of about one hundred and two m/min.

To obtain complex reinforced profile products, it is necessary to use the method of drawing layered materials that consist of fibrous mats or fabrics. Currently, methods have been developed for producing tubular products that combine winding of a spiral layer and broaching. Wind turbine blades that have a complex profile cross section, can be cited as an example of the use of materials with a complex reinforcement pattern. Tooling has already been developed for molding semi-finished products for automotive leaf springs, which have a curved surface and a variable cross-section.

4. Winding.

One of the most promising methods for molding fiberglass products is the fiber winding method, due to the fact that it creates the required filler structure in the products depending on their shape and operating characteristics. Thanks to the use of strands, tapes, threads as fillers, it ensures maximum strength of products. Moreover, such fillers are the cheapest.

The fiber winding process can be described as a relatively simple method in which reinforcing material in the form of a permanent roving (tow) or thread (yarn) is wound onto a rotating mandrel. Special mechanisms monitor the winding angle and the location of the reinforcing material. These devices move at a speed that matches the rotation of the mandrel. The material is wrapped around the mandrel in the form of strips touching each other, or in some special pattern until the mandrel surface is completely covered. Successive layers can be applied at one angle or at different winding angles until the required thickness is achieved. The winding angle varies from very small, which is called longitudinal, to large - circumferential. This arrangement implies 90 0 relative to the axis of the mandrel, covering all spiral angles of this interval.

Thermosetting resin serves as a binder for the reinforcing material. In the wet winding process, the resin is applied directly during the winding itself. The dry winding process is based on the use of roving, which is pre-impregnated with resin in the B-stage. Hardening is carried out at increased temperature without excess pressure. The final stage of the process is based on taking the product from the mandrel. If necessary, finishing operations can be carried out: mechanical processing or grinding. The basic winding process is characterized by many options, which differ only in the nature of the winding, as well as design features, combination of materials and type of equipment. The structure must be wound as on a surface of rotation. However, it is possible to mold products of another type, for example, by compressing a still unhardened wound part inside a closed mold.

The design looks like a smooth cylinder, pipe or tubing, the diameter of which ranges from several centimeters to several tens of centimeters. Winding allows you to form products of conical, spherical and geodesic shapes. To obtain pressure vessels and storage tanks, an end cap must be inserted into the winding. It is possible to form products that will work under non-standard loading conditions, for example, external or internal pressure, compression loads or torque. Thermoplastic pipes and high-pressure metal vessels are strengthened when wound with external bands. The resulting products are characterized by a high degree of accuracy. However, there is another side to the winding process; this process is characterized by lower production speeds. The advantage is that absolutely any permanently reinforcing material is suitable for winding.

Machines can be used for the winding process different types: from various lathes and chain-driven machines to more complex computerized units characterized by three or four axes of movement. Machines that continuously produce pipes are also used. To facilitate winding of large tanks, portable equipment should be designed at the installation site.

The main advantages of the winding method:

a method of laying material that is profitable from an economic point of view due to the speed of the process;
possibility of adjusting the resin/glass ratio;
low dead weight, but high strength;
this method is not prone to corrosion and rotting;
relatively inexpensive materials;
good structure of laminates, due to the fact that the profiles have directional fibers, and good content of glass materials.

5. Pressing.

The pressing process consists of directly giving the desired shape to the product under the influence of high pressure, which is formed in the mold at the temperature of rapid hardening of the material. Due to external pressure in the material that is pressed, its compaction and partial destructuring of the previous structure occurs. The friction between contacting particles of material, which is formed during compaction, causes the generation of thermal energy, which will definitely lead to the melting of the binder. After the material enters a viscoplastic state, it spreads in the mold under pressure, forming a coherent and compacted structure. The hardening process is based on the cross-linking reaction of macromolecules due to polycondensation between the free groups of the binder. The reaction requires heat, during which low molecular weight, volatile substances are released, such as methanol, water, formaldehyde, ammonia, etc.

Parameters for direct pressing technology:

preheating temperature;
pressing pressure;
pressing temperature;
temporary exposure under pressure;
prepress parameters;

Pressure acts directly on the material in the mold cavity during direct pressing, so mold parts may wear out prematurely. Depending on the size of the product, the pressing cycle can range from 4 to 7 minutes. Direct pressing of plastics for reinforcement has two types, which depend on how the fiber filler is impregnated:

Dry, pre-impregnated canvases and fabrics are pressed;
They are pressed with impregnation exactly in the mold.

The first method is more popular. To produce products of relatively simple shapes, direct pressing is used. Due to the high demands placed on the quality of the outer surface of the part, automatic installations were created for dosing components when preparing prepreg blanks. Special automatic manipulators have been designed that load packages of blanks into multi-cavity press molds. The new generation of high precision presses are equipped with modern systems control, thanks to which it is possible to obtain parts with a high-quality surface, and their cost is approximately the same as steel parts.

6. SMC technology.

A serious obstacle to the spread of composite materials is the poor adaptation of traditional technologies for their production to the needs of modern large-scale production, which is also fully automated. Today, composite parts still remain “piece goods”. Expensive labor of experienced personnel makes a high contribution to the cost share of these materials. Despite this, in recent years we have made significant progress in the preparation of automated methods for the production of composites. SMC technology has become one of the most popular developments.

The final products using this technology are subject to a two-stage process. The first stage of the technology is characterized by the fact that prepreg is produced on an automatic conveyor unit, and already at the second stage the prepreg is processed in steel molds in finished parts. Let us describe these stages in more detail. Unsaturated polyester resin is used as the base for the binder material. Its advantages include low price and short curing time. The reinforcing component is chopped fiberglass, which is randomly distributed throughout the sheet volume. Long-term storage for several months at room temperature is ensured by the resin curing system. Chemical thickeners increase the viscosity of the binder after the glass fiber has been impregnated by several orders of magnitude, thereby improving the manufacturability of the prepreg and also increasing its shelf life. Mineral fillers that are added to the binder in large quantities, increase the fire resistance of finished products and, and the quality of their surface noticeably improves.

The resulting prepreg can be processed in an automatic process thanks to pressing in heated steel molds. These molds are similar in design to injection molds for thermoplastics. Thanks to the binder formulation, the prepreg hardens at a temperature of 150 C and a pressure of 50-80 bar at a speed of ~30 sec/mm of thickness. Very low curing shrinkage is important feature SMC technologies. Due to the high content of mineral filler and special thermoplastic additives, shrinkage is up to 0.05%. The resulting products have an impact strength of 50-100 kJ/m2, and a destructive bending strength of 120-180 MPa. It is economically feasible to use SMC technology when producing high-quality composite products in large quantities from several thousand to hundreds of thousands per month. Hundreds of thousands of similar materials are produced on the European market per year. The electric power, automobile and railway industries are the largest consumers of these materials.

7. RTM (Resin Transfer Molding) method.

The RTM method is based on the impregnation and injection molding of composites, during which the binder is transferred into a closed matrix that already contains fillers or preforms. Various fabrics various weaves can act as a reinforcing material, for example, multiaxial or emulsion material, and powder glass mats. The binder is a resin that gels in 50-120 minutes and has a low dynamic viscosity. GOST 28593-90 determines the viscosity and gelation time of the resin.

This method is perfect for standard volumes of 500 -10,000 products per year. The matrix design consists of composite or steel forms that follow the external contours of the part on both sides. The structures have high temperature properties that are held in place by the precise alignment of enclosed steel frames that are supported at the clamping locations.

This method is ideal for the production of matrices from 0.2m2 to 100m2. The matrix design consists of composite or steel forms. The circuit matrix consists of a lighter and more flexible design. The halves of the matrix are connected to each other under the influence of vacuum.

Advantages of RTM technology:

automated production, which reduces the random nature of human intervention;
there is a reduction and control of the amount of raw materials used;
the impact of the material on the environment is reduced;
working conditions have been improved;
relatively durable products are created due to better impregnation;
relatively cheap equipment.

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

2. Types of composite materials.

3. Classification of composite materials.

4. Economic efficiency of using composite materials.

Production of composite materials

Advantages of using composite materials

Use of composites in the defense and aviation industries

Advantages of composite materials

Disadvantages of composite materials

Areas of use

Consumer goods

Mechanical engineering

Characteristic

Specifications

Technical and economic advantages

Areas of application of technology

Aviation and astronautics

Weapons and military equipment

see also

Links

Classification of composites

Advantages of composite materials

Disadvantages of composite materials

High price

Anisotropy of properties

Low impact strength

High specific volume

Hygroscopicity

Toxicity

Low operational efficiency

Areas of use

Consumer goods

Sport equipment

Medicine

Mechanical engineering

Characteristic

Specifications

Technical and economic advantages

Areas of application of technology

Aviation and astronautics

Weapons and military equipment

see also

Notes

Literature

Links

Composite Material Information About

2. Spraying.

3. Pultrusion.

4. Winding.

5. Pressing.

6. SMC technology.

7. RTM (Resin Transfer Molding) method.

Related materials: