Prospects for the use of composite materials. Technologies for the production of composite materials

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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. structural composites, reinforcing elements usually provide the necessary mechanical characteristics material (strength, stiffness, etc.), and the matrix provides joint work reinforcing elements and protecting them from mechanical damage and aggressive chemical environment.

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 CM cannot be better than 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 a fairly large number of disadvantages that hinder their distribution.

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 therefore a developed industrial production and scientific base of the country. However, this is true only when composites replace simple rolled products made of ferrous metals. case of light products, products complex shape, corrosion-resistant products, high-strength dielectric products composites are the winners. Moreover, the cost of composite products is often lower than analogues made of non-ferrous metals or of 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 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 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 parts engines internal combustion(pistons, connecting rods).

Characteristic

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

see also

• Composite rebar
• hybrid material

Notes

1. 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

Links

• Journal of Mechanics of Composite Materials and Structures
• "Composites from the science city"
• "Black Wing Technology"

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Composite Material Information About

By various combinations of binders and fillers, polymer composite materials (PCM) are obtained with the necessary physical, mechanical and physical characteristics for operation in various conditions. Often the production of polymer composite materials and the molding of products from them are combined in one process, which allows to significantly reduce the cost of products made of composites.

The optimal molding method for each specific PCM product is determined a large number factors such as:

• design features of the product;
• the purpose of the resulting product (and the corresponding requirements - surface cleanliness, dimensional accuracy, etc.);
• properties and technological capabilities of the binder component;
• filler structure;
• economic factors (cost, productivity and service life of equipment, labor intensity, etc.)

Features of molding polymer composites based on thermoplastics

Productivity of production and processing methods polymer composites on the basis is mainly determined by the speed of the physical and physico-chemical processes occurring in the binder polymer during processing:

• melting;
• crystallization;
• heating;
• cooling;
• relaxation, etc.

The completeness and nature of these processes are largely determining factors for the quality of the finished product. In addition, the quality of finished products is also affected by destructive processes in the polymer, which proceed at an increased rate as a result of thermal and mechanical effects on the material from the working bodies of machines during processing.

The required shape of the product from can be given by the development of highly elastic or plastic deformation. Due to the high viscosity of the material, the rate of deformation processes is low. Depending on the physical state of the polymer at the time of molding, a different degree of non-equilibrium is achieved in the finished product due to incomplete relaxation of internal stresses. This imposes certain restrictions on the temperature range of operation of products obtained various methods. An increase in the proportion of the highly elastic component of deformation leads to a decrease in the upper temperature limit up to the glass transition temperature of the polymer.

Features of the molding of polymer composite materials based on thermosets

A feature of the methods for obtaining polymeric materials is the combination physical processes actual molding with chemical reactions formation of three-dimensional polymers (curing), and the properties of products are determined by the speed and completeness of curing. Incomplete curing causes the instability of the properties of products from time to time, as well as the occurrence of destructive processes in finished products.

Depending on the processing method, curing is combined with the molding of the product (in the case of pressing thermoplastics, it occurs after the molding of the product in the mold cavity (injection molding, thermoplastic injection molding) or during heat treatment of the molded workpiece (in the formation of large-sized products). Achieving the required completeness of curing of some types of oligomers, even in the presence of catalysts and at elevated temperatures, requires a significant time (up to several hours). In this case, the final curing can already be carried out outside the forming equipment, since shape stability is acquired long before complete completion curing process.

Some Problems in the Production of Polymer Composite Materials

The presence during processing of temperature differences over the cross section of the product leads to an increase in structural heterogeneity and the appearance of additional stresses associated with the difference in the rates of cooling, crystallization, relaxation in various parts, as well as with varying degrees of curing (in the case of thermoplastics). This causes the heterogeneity of the properties of the material in the product, which is not always acceptable, and is the cause of many types of defects (warping, cracking, etc.). The existence of internal stresses, primarily orientational, also limits the temperature range of operation. A certain increase in the heterogeneity of the supramolecular structure and a decrease in internal stresses can be achieved due to the heat treatment of the finished product, but it is more efficient to use methods of directed control of structures during processing.

When molding products from polymer composites a significant change in the structure is possible and hence the properties of the polymer. Therefore, materials and products obtained on the basis of the same polymer may differ significantly in performance. if the technology is different. The most important factors affecting the structure and properties of PCM are the parameters of the processing process:

• temperature,
• pressure,
• heating and cooling modes, etc.

Proper accounting and selection of all technological parameters allows to achieve in the finished product:

• uniform structure,
• minimum level of residual stresses (structural, shrinkage, thermal),
• a high degree of completion of the processes of curing, crystallization,

to get high quality products.

I dedicated history composite materials. I continue to occupy my leisure time on this topic and today I want to talk a little about the terms and technologies of prototyping using polymer composites. If you have nothing to do long winter evenings, then you can always make a snowboard, a motorcycle case or a smartphone case out of carbon fiber fabric. Of course, the process can end up being more expensive than buying a finished product, but it's interesting to make something with your own hands.

Under the cut - an overview of methods for manufacturing products from composite materials. I would be grateful if you add me in the comments so that the result is a more complete post.

A composite material is created from at least two components with a clear boundary between them. There are layered composite materials - for example, plywood. In all other composites, the components can be divided into a matrix, or binder, and reinforcing elements - fillers. Composites are usually divided according to the type of reinforcing filler or matrix material. You can read more about the use of composites in the post, and this post is about methods for making products from composites.

hand molding

In the case of the manufacture of single items, the most common method is hand molding. A gel coat is applied to the prepared matrix - a material to obtain a good finish on the outer part of the reinforced material, which also allows you to choose the color for the product. Then a filler is placed in the matrix - for example, fiberglass - and impregnated with a binder. We remove air bubbles, wait until everything cools down, and refine it with a file - cut it, drill it, and so on.

This method is widely used to create body parts for cars, motorcycles and mopeds. That is, for tuning in cases where it is not limited to sticking a film “under carbon”.

Spraying

Spraying does not require cutting glass material, but instead you need to use special equipment. This method often used to work with large objects, such as boat hulls, vehicles, and so on. In the same way as in the case of hand molding, the gel coat is applied first, then the glass material.

RTM (injection)

With the method of injection of polyester resin into a closed mold, a tooling is used from a matrix and a reciprocal mold - a punch. The glass material is placed between the matrix and the counter form, then a hardener is poured into the form under pressure - polyester resin. And, of course, finishing with a file after curing is to taste.

Vacuum infusion

The vacuum infusion method requires a bag in which a vacuum is created using a pump. The package itself contains a reinforcing material, the pores of which, after the air is pumped out, are filled with a liquid binder.

An example method is for making a skateboard.

winding

The method of winding composites makes it possible to make ultra-light cylinders for compressed gas, for which a PET liner pumped up to 2-5 atmospheres is used, as well as composite pipes used in the oil industry, chemical industry and public utilities. From the name it is easy to understand that fiberglass is wound around a moving or stationary object.

On the video - the process of winding fiberglass on a balloon.

pultrusion

Pultrusion is "pulling". With this method, there is a continuous process of pulling the composite material through the pulling machine. The speed of the process is up to 6 meters per minute. The fibers are passed through a polymer bath, where they are impregnated with a binder, after which they pass through a preformer, obtaining the final shape. Then the material is heated in the mold, and at the exit we get the final hardened product.

Production process of sheet piles by pultrusion method.

direct pressing

Thermoplastic products are made in molds under pressure. For this, high temperature hydraulic presses with a force of 12 to 100 tons and maximum temperature about 650 degrees. In this way, for example, plastic buckets are made.

Autoclave molding

The autoclave is necessary for carrying out processes with heating and under pressure above atmospheric in order to speed up the reaction and increase the yield of the product. Composite materials are placed inside the autoclave on special forms.

Composite Products

Composite materials are widely used in the aircraft industry. For example, built from them.

Auto industry

Prostheses and orthoses.

If you have additions, be sure to write about them in the comments. Thank you.

Materials based on several components, which determines their operational and technological characteristics. Composites are based on a matrix based on metal, polymer or ceramics. Additional reinforcement is performed by fillers in the form of fibers, whiskers and various particles.

Are composites the future?

Plasticity, strength, wide scope of application - this is what distinguishes modern composite materials. What is it in terms of production? These materials consist of a metallic or non-metallic base. Flakes of greater strength are used to reinforce the material. Among them are plastic, which is reinforced with boron, carbon, glass fibers, or aluminum, reinforced with steel or beryllium filaments. If you combine the content of the components, you can get composites of different strength, elasticity, resistance to abrasives.

Main types

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

Composites with a non-metallic matrix are based on polymers, carbon or ceramics. Among the polymer matrices, the most popular are epoxy, polyamide, and phenol-formaldehyde. The shape of the composition is given by the matrix, which acts as a kind of binder. To strengthen materials, fibers, tows, threads, multilayer fabrics are used.

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

• impregnation of reinforcing fibers with matrix material;
• molding in the mold of the reinforcing tapes and the matrix;
• cold pressing of components with further sintering;
• electrochemical coating of fibers and further pressing;
• deposition of the matrix by plasma spraying and subsequent compression.

What hardener?

Composite materials have found application in many industries. What it is, we have already said. These are materials based on several components, which are necessarily strengthened with special fibers or crystals. The strength of the composites themselves also depends on the strength and elasticity of the fibers. Depending on the type of hardener, all composites can be divided:

• on fiberglass;
• carbon fibers with carbon fibers;
• boron fibers;
• organ fibers.

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

wood composites

Separately, it is worth mentioning the wood composite. It is obtained by combining raw materials different type, with wood as the main component. Everyone wood-polymer composite consists of three elements:

• particles of crushed wood;
• thermoplastic polymer (PVC, polyethylene, polypropylene);
• a complex of chemical additives in the form of modifiers - they are up to 5% in the composition of the material.

The most popular type of wood composites is a composite board. Its uniqueness lies in the fact that it combines the properties of both wood and polymers, which significantly expands the scope of its application. So, the board is distinguished by its density (its indicator is affected by the base resin and the density of wood particles), good resistance to bending. At the same time, the material is environmentally friendly, retains texture, color and aroma. natural wood. The use of composite boards is absolutely safe. Due to polymer additives, the composite board acquires high level wear resistance and moisture resistance. It can be used for finishing terraces, garden paths even if they are heavily loaded.

Production features

Wood composites have a special structure due to the combination of a polymer base with wood in them. Among the materials of this type can be noted wood-chip, different density, oriented chip boards and wood-polymer composite. The production of composite materials of this type is carried out in several stages:

1. The wood is shredded. For this, crushers are used. After crushing, the wood is screened and divided into fractions. If the moisture content of the raw material is above 15%, it must be dried.
2. The main components are dosed and mixed in certain proportions.
3. The finished product is pressed and formatted to acquire a presentation.

Main characteristics

We have described the most popular polymer composite materials. What it is is now clear. Thanks to the layered structure, it is possible to reinforce each layer with parallel continuous fibers. It is worth mentioning the characteristics modern composites which are different:

• high value of temporary resistance and endurance limit;
• high level of elasticity;
• strength, which is achieved by reinforcing the layers;
• Due to the rigid reinforcing fibers, the composites are highly resistant to tensile stresses.

Metal-based composites are characterized by high strength and heat resistance, while they are practically inelastic. Due to the structure of the fibers, the propagation rate of cracks, which sometimes appear in the matrix, is reduced.

Polymer materials

Polymer composites are presented in a variety of options, which opens great opportunities on their use in various fields, from dentistry to the production of aviation equipment. Polymer-based composites are filled with different substances.

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

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

Consider popular types

fiberglass

Glass fibers formed from molten inorganic glass are used to reinforce these composite materials. The matrix is ​​based on thermosetting synthetic resins and thermoplastic polymers, which are distinguished by high strength, low thermal conductivity, and high electrical insulating properties. Initially, they were used in the production of antenna radomes in the form of domed structures. AT modern world fiberglass plastics are widely used in the construction industry, shipbuilding, the production of household equipment and sports items, and radio electronics.

In most cases, fiberglass is produced on the basis of sputtering. This method is especially effective in small- and medium-scale production, for example, hulls of boats, boats, cabins for road transport, railway wagons. The sputtering technology is convenient because it does not require cutting glass material.

CFRP

The properties of composite materials based on polymers make it possible to use them in a variety of fields. They use as a filler carbon fibers obtained from synthetic and natural fibers based on cellulose, pitches. The fiber is thermally processed in several stages. Compared to fiberglass, carbon fiber is characterized by a lower density and higher lightness and strength of the material. Due to the unique operational properties of carbon fiber plastics, they are used in mechanical engineering and rocket building, the production of space and medical equipment, bicycles and sports equipment.

Boroplasty

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

Organoplasty

In these composites, mainly synthetic fibers act as fillers - tows, threads, fabrics, paper. Among the special properties of these polymers, one can note low density, lightness compared to glass and carbon fiber reinforced plastics, high tensile strength and high resistance to impact and dynamic loads. This composite material is widely used in such areas as mechanical engineering, shipbuilding, automotive industry, in the production of space technology, and chemical engineering.

What is the efficiency?

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

• in aviation in the production of aircraft and engine parts;
• space technology for the production of load-bearing structures of vehicles that are heated;
• automotive industry to create lightweight bodies, frames, panels, bumpers;
• mining industry in the production of drilling tools;
• civil engineering for the creation of spans of bridges, elements of prefabricated structures on high-rise buildings.

The use of composites allows increasing the power of engines, power plants, while reducing the weight of machines and equipment.

What are the prospects?

According to representatives of the Russian industry, the composite material belongs to the materials of a new generation. It is planned that by 2020 the volumes of domestic production of composite industry products will increase. Pilot projects aimed at the development of new generation composite materials are already being implemented in the country.

The use of composites is expedient in a variety of areas, but it is most effective in industries related to high technology. For example, today not a single aircraft is created without the use of composites, and some of them use about 60% of polymer composites.

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

Composite materials, or, as they are usually called, composites, have revolutionized many industries and become popular in high-tech products that must be characterized by low weight, but at the same time high resistance to mechanical stress. Expected economic benefits in high-tech projects such as military and space developments are primarily associated with lightweight, high-temperature resistant composite materials, which reduce the weight of 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, should be light, and on the other hand, strong enough) were the main guiding force in their design and development. It is now generally accepted that the wings of aircraft, their tails, propellers, and engine turbine blades are made of modern composite materials. The same applies to most of their internal structure and parts of the fuselage. The bodies of some small aircraft are already completely made of composite materials. In large commercial aircraft, wings, tails and body panels are usually made of such materials.

Composite connectors for internal connections, supplied to the market in accordance with its needs and requirements of consumers, successfully replace the previous connectors, which were made of brass, nickel, aluminum, bronze or stainless steel. Composite connectors are ideal for use in environments environment where high temperature resistance and EMC requirements are required. When using them, toxic gaseous products and, in particular, and most importantly, halogens are practically not emitted. Composite materials are stronger than steel, they provide high corrosion resistance, have higher 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 beneficial way. There are two components in composite materials: 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 the polymers that hold the reinforcing elements together, and they help to set the desired physical properties final product.

Thermoplastics are characterized by being hard at low temperatures but soften when heated. Although they are less commonly used than thermoset plastics, they do have some advantages, such as higher fracture toughness, long shelf life as a raw material, and recyclability. The use of thermoplastic plastics is safer and less polluting workplace, because when preparing them for direct use there is no need for organic solvents for their hardening.

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

The performance of any connector is the sum of the performance of its constituent parts. The use of composite materials in the ACT series increased the strength of the connector body and the locking threaded 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, the design of this series of connectors includes clamps that favorably affect the performance and duration life cycle connector.

Thermoplastics, or thermosetting plastics, in their original form are in liquid state, but harden and harden (vulcanize) when 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, for example, glass fibers, thermosets successfully resist wear and harsh chemicals and are highly durable even in extremely harsh environments. Such materials provide both design flexibility and high dielectric strength.

If composites are classified according to the matrix material, then they are distinguished: thermoplastic composites, composites using short (chopped) fibers and thermoplastics with long fibers or reinforced fibers. The most famous 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, ceramic is used when the material is exposed to very high temperatures, while carbon is used for products that are subject to friction and wear.

Polymers not only used as a matrix material, they are also used as well-established reinforcing materials for reinforcing composites. For example, Kevlar is a polymer fiber that is very strong and adds stiffness to the composite material combined with toughness. While fiberglass is 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 and thermal conductivity, are resistant to radiation exposure, and do not emit toxic gases. However, they tend to be more expensive than their replacement counterparts and are used where their higher specifications and properties can justify the cost increase.

To date, these materials most often find application in aircraft assemblies and space systems.

Durability and resistance to elevated temperatures- most important characteristics in polymers used for high-tech applications. Products intended for commercial and military space applications must be made using so-called specialty engineering plastics or other specialized high temperature polymers. Engineering plastics such as polyesterimide (PEI), polyphthalamide (PPA), polyphenylene sulfide (PPS) and polyesterimide (Polyamide-imide - PAI) have been developed and designed specifically for use in high operating temperature. Polyetheretherketone (PEEK) type resins and various liquid crystal polymers (LCPs) are also capable of withstanding extremely high temperatures. These advanced high-tech plastics also meet toxic gas emission requirements and are flame retardant.

Benefits of using composite materials

We depend on composite materials for a number of aspects of our Everyday life. Composite materials based on glass fiber were developed in the late 40s of the last century, they are the first modern composite materials and are still widely used. In the total volume of currently produced composite materials, materials based on glass fibers occupy approximately 65%. You may be using products made from fiberglass composite without even knowing it.

The ever-increasing number of manufacturers of composite materials and the growth of their offerings on the market allows consumers to choose desired 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 essential. For most of these applications, typical weight savings with composites over aluminum are approximately 40%, and 80% over brass and stainless steel.
• Composite materials are extremely durable. As an example, high-strength fiber-structured composites are widely used in body armor. Due to the high strength of such composite materials, soldiers are well protected from shrapnel and bullets.
• Composites are very resistant to aggressive chemicals they will never rust or corrode. This is exactly why the maritime industry was one of the first to adopt them for use.
• Polymer plastics are less susceptible to mechanical resonance, so threaded parts made from these materials are less likely to loosen and unscrew when subjected to shock and high vibration.
• Some composites are not electrically conductive. This is important because often composite materials are needed where strength and high electrical insulating properties are needed.
• Composites can weaken magnetic fields, reduce the effect of magnetic fields on corrosion and muffle the so-called "acoustic signature", that is, the acoustic radiation characteristic of each device, which is very important property when developing products for which a low probability of detection is important.

Composite parts are much less likely to fail under stress than metal parts. Small crack in metal part can develop into catastrophic, and 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 along its fibers, it is the fibers that carry all the load, so their type, number, orientation and linearity determine their effectiveness. Glass fiber composites are used for applications that simultaneously require stiffness, high electrical insulating 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 holds the fibers in their proper 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.

The 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 a low specific gravity. It is most difficult to design complex parts from composites that use the listed properties for their own purposes, but at the same time must fulfill necessary requirements geometric dimensions, installation and functional use. But by choosing the appropriate combination of reinforcing material and matrix material, manufacturers can provide all the necessary product characteristics that will meet the requirements for both its specific design and its specific purpose of use.

Electrical connectors used for power and data transmission in military and aerospace products are constantly shrinking in size and weight. Many military customers are looking for smaller, lighter and more flexible solutions that meet the tough 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 provide both their high technical characteristics and the necessary requirements for environmental protection.

Composites are the basis of many modern projects in the development of devices with a minimally noticeable effect. 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 rigidity, due to which they are suitable materials for systems that are used in avionics.

These materials provide weight savings, high strength, and operational stability that far exceed those of many metals and non-composite thermosets.

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

It is an undoubted fact that composite materials are increasingly being developed for the specific requirements of internal connection systems, despite the complexity of both their design and the production process for their manufacture, 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 can never completely replace traditional materials, such as, for example, steel, but the significant advantages of composites give real savings funds, reducing fuel consumption and saving on maintenance of the system as a whole, increase the service life for a large number defense and space products. Without a doubt, we should be aware of all the possibilities that composites can give us.

Sourced from www.connectorsupplier.com
Jenny Bieksha, Bishop & Associates Inc.
Translation: Vladimir Rentyuk
The article was published in the journal "Bulletin of Electronics" No. 1 2014