Why is carbon fiber a unique material? In a carbon kitchen: Durability Fiberglass rod repair.

Carbon fiber is a composite multilayer material, which is a web of carbon fibers in a shell of thermosetting polymer (usually epoxy) resins, Carbon-fiber-reinforced polymer.

The international name Carbon is carbon, from which carbon fiber is obtained.

But at present, carbon fibers include everything in which the supporting base is carbon fibers, but the binder can be different. Carbon and carbon fiber have been combined into one term, causing confusion in the minds of consumers. That is, carbon or carbon fiber are the same thing.

This is an innovative material, the high cost of which is due to the labor-intensive technological process and a large share of manual labor. As manufacturing processes improve and become automated, the price of carbon will decrease. For example: the cost of 1 kg of steel is less than $1, 1 kg of European-made carbon fiber costs about $20. Reducing the cost is only possible through complete automation of the process.

Application of carbon

Carbon fiber was initially developed for sports cars and space technology, but due to its excellent performance properties, such as low weight and high strength, it has become widespread in other industries:

• in aircraft manufacturing,
• for sports equipment: clubs, helmets, bicycles.
• fishing rods,
• medical equipment, etc.

The flexibility of carbon fabric, the possibility of its convenient cutting and cutting, and subsequent impregnation with epoxy resin allow you to mold carbon products of any shape and size, including yourself. The resulting blanks can be sanded, polished, painted and flexo-printed.

Technical characteristics and properties of carbon

The popularity of carbon fiber plastic is explained by its unique performance characteristics, which are obtained by combining materials with completely different properties in one composite - carbon fiber as a load-bearing base and as a binder.

The reinforcing element common to all types of carbon fiber is carbon fibers with a thickness of 0.005-0.010 mm, which work well in tension, but have low bending strength, that is, they are anisotropic, strong only in one direction, so their use is justified only in the form of a canvas.

Additionally, reinforcement can be carried out with rubber, which gives a gray tint to carbon fiber.

Carbon or carbon fiber is characterized by high strength, wear resistance, rigidity and low weight compared to steel. Its density is from 1450 kg/m³ to 2000 kg/m³. The technical characteristics of carbon fiber can be seen in density, melting point and strength characteristics.

Another element used for reinforcement along with carbon threads is . These are the same yellow threads that can be seen in some types of carbon fiber. Some unscrupulous manufacturers pass off colored glass fiber, dyed viscose, and polyethylene fibers as Kevlar, the adhesion of which to resins is much worse than that of carbon fiber, and the tensile strength is several times lower.

Kevlar is an American brand name for a class of aramid polymers related to polyamides and lavsan. This name has already become a common noun for all fibers of this class. Reinforcement increases resistance to bending loads, so it is widely used in combination with carbon fiber.

How are carbon fibers made?

Fibers consisting of the finest carbon filaments are obtained by heat treatment in air, that is, oxidation, of polymer or organic filaments (polyacrylonitrile, phenolic, lignin, viscose) at a temperature of 250 ° C for 24 hours, that is, practically charring them. This is what a carbon filament looks like under a microscope after charring.

After oxidation, carbonization occurs - heating the fiber in nitrogen or argon at temperatures from 800 to 1500 °C to build structures similar to graphite molecules.

Then graphitization (saturation with carbon) is carried out in the same environment at a temperature of 1300-3000 °C. This process can be repeated several times, stripping the graphite fiber of nitrogen, increasing the carbon concentration and making it stronger. The higher the temperature, the stronger the fiber. This treatment increases the carbon concentration in the fiber to 99%.

Types of carbon fibers. Canvas

The fibers can be short, cut, theircalled“stapled”, or there may be continuous threads on bobbins.These can be tows, yarn, roving, which are then used to make woven and non-woven fabric and tapes. Sometimes the fibers are laid in a polymer matrix without interlacing (UD).

Since fibers work well in tension, but poorly in bending and compression, the ideal use of carbon fiber is to use it in the form of Carbon Fabric. It is obtained by various types of weaving: herringbone, matting, etc., which have the international names Plain, Twill, Satin. Sometimes the fibers are simply intercepted crosswise with large stitches before being filled with resin. The correct technical characteristics of the fiber and type of weaving for carbon fiber are very important for obtaining high-quality carbon fiber.

Epoxy resins are most often used as a supporting base, in which the fabric is laid layer by layer, with a change in the direction of weaving, to uniformly distribute the mechanical properties of oriented fibers. Most often, 1 mm of carbon sheet thickness contains 3-4 layers.

Advantages and disadvantages of carbon fiber

The higher price of carbon compared to fiberglass and fiberglass is explained by more complex, energy-intensive multi-stage technology, expensive resins and more expensive equipment (autoclave). But strength and elasticity are also higher, along with many other undeniable advantages:

• 40% lighter than steel, 20% lighter than aluminum (1.7 g/cm3 - 2.8 g/cm3 - 7.8 g/cm3),
• carbon made from carbon and Kevlar is slightly heavier than carbon and rubber, but much stronger, and upon impact it cracks, crumbles, but does not crumble into fragments,
• high heat resistance: carbon retains its shape and properties up to a temperature of 2000 ○C.
• has good vibration damping properties and heat capacity,
• corrosion resistance,
• high tensile strength and high elastic limit,
• aesthetics and decorativeness.

But compared to metal and fiberglass parts, carbon parts have disadvantages:

• sensitivity to pinpoint impacts,
• difficulty of restoration in case of chips and scratches,
• fading, fading under the influence of sunlight, coated with varnish or enamel for protection,
• long manufacturing process,
• in places of contact with metal, metal corrosion begins, so fiberglass inserts are fixed in such places,
• Difficulty in recycling and reuse.

How carbon is made

There are the following main methods for manufacturing carbon fabric products.

1. Pressing or “wet” method

The canvas is laid out in a mold and impregnated with epoxy or polyester resin. Excess resin is removed either by vacuum forming or pressure. The product is removed after polymerization of the resin. This process can occur either naturally or accelerated by heating. Typically, this process results in carbon fiber sheets.

2. Molding

A model of the product (matrix) is made from plaster, alabaster, and polyurethane foam, onto which a resin-impregnated fabric is laid out. When rolling with rollers, the composite is compacted and excess air is removed. Then either accelerated polymerization and curing is carried out in an oven, or natural. This method is called “dry” and products made from it are stronger and lighter than those made by the “wet” method. The surface of a product made by the “dry” method is ribbed (if it is not varnished).

This category also includes molding from sheet blanks - prepregs.

Based on their ability to polymerize with increasing temperature, resins are divided into “cold” and “hot”. The latter are used in prepreg technology, when semi-finished products are made in the form of several layers of carbon fiber coated with resin. Depending on the brand of resin, they can be stored for up to several weeks in an unpolymerized state, layered with plastic film and passed between rollers to remove air bubbles and excess resin. Sometimes prepregs are stored in refrigerators. Before molding the product, the workpiece is heated, and the resin becomes liquid again.

3. Winding

Thread, tape, fabric are wound onto a cylindrical blank for the manufacture of carbon pipes. The resin is applied layer by layer with a brush or roller and dried mainly in an oven.

In all cases, the application surface is lubricated with release agents for easy removal of the resulting product after hardening.

DIY carbon fiber

Products based on carbon fiber can be molded yourself, which has long been successfully used in the repair of bicycles, sports equipment, and car tuning. The ability to experiment with resin fillers and the degree of its transparency provides a wide field for creativity for fans of carbon fiber auto tuning. You can read more about the main methods of manufacturing carbon parts.

As follows from the technology described above, for molding it is necessary:

• matrix form,
• carbon sheet,
• mold lubricant for easy removal of the finished workpiece,
• resin.

Where can I get carbon fiber? Taiwan, China, Russia. But in Russia it refers to “high-strength structural fabrics based on carbon fiber.” If you find a way into the enterprise, then you are very lucky. Many companies offer ready-made DIY carbon fiber trim kits for cars and motorcycles, including carbon fiber fragments and resin.

70% of the global carbon fabric market is produced by Taiwanese and Japanese large brands: Mitsubishi, TORAY, TOHO, CYTEC, Zoltec, etc.

In general terms, the process of making carbon fiber with your own hands looks like this:

1. The form is lubricated with anti-adhesive.
2. After it dries, a thin layer of resin is applied, onto which the carbon fiber is rolled or pressed to release air bubbles.
3. Then another layer of impregnation resin is applied. Several layers of fabric and resin can be applied, depending on the required parameters of the product.
4. The resin can polymerize in air. This usually happens within 5 days. You can place the workpiece in a heating cabinet heated to a temperature of 140 - 180 ◦C, which will significantly speed up the polymerization process.

Then the product is removed from the mold, sanded, polished, varnished, gelcoated or painted.

We hope you have found a comprehensive answer to the question “What is carbon”?

Irina Khimich, technical consultant

Advanced industries and construction have recently mastered many fundamentally new technologies, most of which are associated with innovative materials. An ordinary user could notice the manifestation of this process in the example of building materials with the inclusion of composites. Also in the automotive industry, carbon elements are being introduced to improve the performance of sports cars. And these are not all the areas in which carbon fiber reinforced plastics are used. The basis for this component is carbon fibers, a photo of which is presented below. Actually, the uniqueness and active spread of new generation composites lie in their unsurpassed technical and physical qualities.

Receiving technology

To produce the material, raw materials of natural or organic origin are used. Further, as a result of special processing, only carbon atoms remain from the original workpiece. The main influencing force is temperature. The technological process involves performing several stages of heat treatment. At the first stage, oxidation of the primary structure occurs under temperature conditions of up to 250 °C. At the next stage, the production of carbon fibers proceeds to the carbonization procedure, as a result of which the material is heated in a nitrogen environment at high temperatures up to 1500 °C. In this way, a graphite-like structure is formed. The entire manufacturing process is completed by a final treatment in the form of graphitization at 3000 °C. At this stage, the pure carbon content in the fibers reaches 99%.

Where is carbon fiber used?

If in the first years of popularization the material was used exclusively in highly specialized areas, today there is an expansion of production in which this chemical fiber is used. The material is quite plastic and heterogeneous in terms of exploitation capabilities. With a high probability, the areas of application of such fibers will expand, but the basic types of presentation of the material on the market have already taken shape. In particular, we can note the construction industry, medicine, the manufacture of electrical equipment, household appliances, etc. As for specialized areas, the use of carbon fibers is still relevant for manufacturers of aircraft, medical electrodes and

Manufacturing forms

First of all, these are heat-resistant textile products, among which we can highlight fabrics, threads, knitwear, felt, etc. A more technological direction is the production of composites. Perhaps this is the widest segment in which carbon fiber is presented as the basis for products for mass production. In particular, these are bearings, heat-resistant components, parts and various elements that operate in aggressive environments. Composites are mainly aimed at the automotive market, however, the construction industry is also quite willing to consider new proposals from manufacturers of this chemical fiber.

Material properties

The specifics of the technology for obtaining the material left its mark on the performance qualities of the fibers. As a result, high thermal resistance has become the main distinguishing feature of the structure of such products. In addition to thermal effects, the material is also resistant to aggressive chemical environments. True, if oxygen is present during the oxidation process when heated, this has a detrimental effect on the fibers. But the mechanical strength of carbon fiber can compete with many traditional materials that are considered solid and resistant to damage. This quality is especially pronounced in carbon products. Another property that is in demand among technologists of various products is absorption capacity. Thanks to its active surface, this fiber can be considered an effective catalytic system.

Manufacturers

The leaders in the segment are American, Japanese and German companies. Russian technologies in this area have practically not developed in recent years and are still based on developments from the times of the USSR. Today, half of the fibers produced in the world are produced by Japanese companies Mitsubishi, Kureha, Teijin, etc. The other part is shared by Germans and Americans. Thus, on the US side, Cytec is acting, and in Germany, carbon fiber is produced by SGL. Not long ago, the Taiwanese company Formosa Plastics entered the list of leaders in this area. As for domestic production, only two companies are engaged in the development of composites - Argon and Khimvolokno. At the same time, significant achievements have been made in recent years by Belarusian and Ukrainian entrepreneurs who are exploring new niches for the commercial use of carbon fiber reinforced plastics.

The future of carbon fibers

Since some types of carbon fiber reinforced plastics will in the near future make it possible to produce products that can retain their original structure for millions of years, many experts predict an overproduction of such products. Despite this, interested companies continue to race for technological upgrades. And in many ways this is justified, since the properties of carbon fibers are an order of magnitude superior to those of traditional materials. It is enough to remember the strength and heat resistance. Based on these advantages, developers are exploring new areas of development. The introduction of the material will most likely cover not only specialized areas, but also areas close to the mass consumer. For example, conventional plastic, aluminum and wooden elements can be replaced with carbon fiber, which will surpass conventional materials in a number of performance qualities.

Conclusion

Many factors hinder the widespread use of innovative chemical fiber. One of the most significant is the high cost. Since carbon fiber requires the use of high-tech equipment for production, not every company can afford to produce it. But this is not the most important thing. The fact is that not in all areas manufacturers are interested in such radical changes in product quality. Thus, while increasing the durability of one infrastructure element, a manufacturer cannot always perform a similar upgrade on adjacent components. The result is an imbalance that nullifies all the achievements of new technologies.

The twenty-first century is replete with innovation, and the construction industry is no exception.

One of the newest and increasingly popular materials - carbon fiber - has taken its rightful place, partially displacing fiberglass and similar reinforcing materials.

Carbon fabric: characteristics and features

Strictly speaking, carbon fiber is not an invention of this century. It has long been used in aircraft and rocket production, but the average person is familiar with this material in the form of carbon fiber fishing rods and Kevlar. Having gone through a long stage of mastering and improving the technology, the industry has finally become ready to provide carbon fabric to other industries, including construction.

The main feature of carbon fibers is their high specific tensile strength relative to their own weight. Products reinforced with carbon fiber retain the highest known tensile strength, while in terms of material consumption and total weight they are much more profitable than steel, which is common today.

In its original form, carbon fiber is a thin microfiber that can be woven into threads, which in turn can be woven into canvas of any size. Due to the correct orientation of the molecules and their strong connection, such high strength is achieved. Otherwise, the fibers simply serve as reinforcement for any type of structural fill, from epoxy resins to concrete.

One of the most pronounced features of carbon fiber is its high sorption capacity. The benefit of using carbon fiber to strengthen interior finishing elements is that carbon does not allow natural impurities, dyes or solvents to penetrate into the air environment of residential premises. At the same time, sorption processes occur absolutely harmlessly for the fiber itself.

Benefits of use

In general, two properties of carbon fiber are interesting for construction. The first - structural versatile reinforcement - is used to give the material increased hardness and compressive strength. The structure is reinforced with fiber 5–10 microns thick with different fiber lengths. It makes sense to structurally strengthen the finishing surfaces and supporting structures of buildings.

The second purpose of carbon fibers in the construction industry - embedded reinforcement - is performed by additionally processed primary fiber, which takes the form of canvas, roving, threads, ropes and rods reinforced with polymer resins. In this case, carbon fiber does not strengthen the filler itself as a whole, but serves as a reliable, tear-resistant base for it.

But what are the benefits of carbon fibers, and why should they be preferred to less exotic materials? Let's start with the fact that in terms of physical and chemical properties, the closest competitor to carbon fiber is glass fiber, which is quite widespread in the form of fiberglass for interior plastering work. However, glass has a much lower tensile strength and is heavier, while carbon polymer is not only strong, but also adheres much better to the surrounding solid material due to its high intrinsic adhesion.

The cladding and structure reinforced in this way are also characterized by increased shear and torsional strength, which has always been a significant problem for steel, glass and other synthetic materials.

However, it is not without complications. In particular, when interior finishing of buildings, the question of the fire safety of carbon fiber is raised. In the presence of oxygen, it burns out already at temperatures of about 350–400 °C, but being “preserved” in an airless environment, carbon retains its properties even when heated above 1700 °C. Higher heat resistance is guaranteed by fiber and its derivatives coated with various types of carbides - this must be taken into account when choosing a material for finishing work.

Application in finishing works

A wide range of decorative finishing materials require a base that is absolutely not susceptible to cracking. This includes acrylic painting, polymer floor coverings, Venetian plaster and other thin and fragile compositions.

If this problem is not particularly acute for false walls made of gypsum plasterboard, then other materials require a special approach due to more pronounced linear expansion. For example, let’s take the strengthening and insulation of joints of single-layer sheathing made of OSB. Almost any putty or glue will crumble right inside the seam within a year or two.

Such joints should be filled with durable polymer glue, and then cover the adjacent edges by 25-30 mm with a tape of thin carbon threads and cover again with a layer of filler, carefully smoothing the seal with a spatula.

In most cases, such processing does not require subsequent leveling of the surface. The sheathing assumes monolithic strength, and the resulting structural overstresses are fully compensated by the properties of OSB.

A similar principle can be applied when finishing leveling plastered walls with acrylic putty. In this case, carbon fiber is the undisputed leader in imparting impact resistance and resistance to cracking. Installation is carried out by analogy with fiberglass:

1. First, thin continuous coating of the surface.
2. Then laying the canvas and smoothing it out.
3. After which you can immediately begin the final alignment.

The canvas does not show itself in any way on the appearance of the finished surface, either before the composition dries or after.

Using carbon fiber

Increasing the strength of load-bearing elements of buildings, cast on site or in a factory, is possible by adding carbon fiber to the liquid filler composition. Carbon fiber can already be purchased in fairly large quantities, which will reduce the thickness of walls, columns and other elements of a concrete structure that experience vertical axial compressive loads. Due to this, a lot of space is freed up for structural insulation or insulation of structures.

This material will be especially interesting for fans of pile-grillage foundations, where the work of carbon yarn is completely visual. A column that maintains a compressive strength of 12–15 tons, taking into account all the recommended safety margins, has a thickness of about 80 mm. There are only two threads of polymer reinforcement inside it, and strands of carbon roving are laid on the other two sides.

How much carbon fiber is required to reinforce concrete? Not at all, only 0.05–0.12% of the mass of the finished concrete products. The concentration may be higher if we are talking, for example, about hydraulic structures or concrete floor trusses.

External reinforcement systems

The structure, reinforced with carbon fiber, is so strong that it can even be used as girdle reinforcement for elements of heavily loaded structures. From high-rise housing construction to prefabricated frame structures, the external reinforcement belt provides unprecedented resistance to operational overloads.

The bottom line is that the core of the element itself, containing embedded reinforcement, is cast as usual, but with a minimal protective layer of concrete on the sides. After removing the formwork, the product, be it a column or a reinforcing belt, is wrapped with a layer of carbon fabric or thick thread, and then filled with sand concrete containing fiber. This approach eliminates the need to use heavy granite concrete while fully inheriting its strength characteristics. Moreover, even a minimal layer of carbon-reinforced concrete significantly reduces corrosion of embedded reinforcement.

A special case of external reinforcement can be called pasting joints with flaps or tape made of carbon fiber, carbon fabric with accompanying impregnation with epoxy resins. Such a connection demonstrates three times higher strength than a conventional one, which is invaluable for rafter systems and especially for attaching trusses to the Mauerlat.

Carbon materials and carbonized fiber materials. Structural carbon fabrics 3k, 6k, 12k, 24k, 48k, manufacturing and supply. Carbon insulating fabrics. for thermal protection of various equipment, including protective screens and curtains. Carbon tapes, including foil carbon tapes. Carbon braided heat resistant cords. Carbon filaments, production and supply.

Carbon fiber general information

Many polymer fibers are suitable for producing carbon fiber. Enterprises of the IFI Technical Production group use polyacrylonitrile (PAN) fiber to produce carbon fibers. In this section of the site, we will consider only two types of carbon fiber and products made from them. We do not consider graphitized fibers, since these products are given a separate section on our website.
And so, according to physical characteristics, carbon fiber is divided into high-strength carbon (carbon) fibers and general-purpose carbon fibers (carbonized).

The two types of yarn are very different in appearance. In the photo on the right, under the number 1, the yarn is made from high tenacity carbon fiber 12k, that is, a yarn consisting of 12,000 continuous filaments. Numbered 2, carbonized yarn for general use. This is a twisted carbonized thread made of two or more fibers with a length from 25mm to 100mm.

It is carbon (carbonized) general purpose yarn that is used for the production of carbon gland packings.

Carbonized carbon fibers

Carbonized fiber is produced in two main stages:

1. PAN fiber is oxidized at a temperature of +150°C ~ +300°C.

2. Oxidized PAN fiber is carbonized in a nitrogen environment at a temperature of +1000°C ~ +1500°C

General purpose carbonized fiber is used mainly to produce thermal insulation products and products such as fabrics, tapes, and cords. Carbonized fabrics are used for high temperature insulation. It is an excellent thermal protection in various industrial applications. Carbonized fabric is used as a cushioning material or as a winding for structural elements, pipelines, etc. Carbonized fabric is used in the form of protective screens and curtains. Products made from carbonized fiber are operational at temperatures from -100°C to +450°C.

Carbonized fabrics are an excellent modern substitute for fiberglass fabrics. Unlike fiberglass products, carbonized fabric does not cause irritation of the mucous membrane, does not provoke itching of the skin, carbonized fabric, cords, tapes are completely harmless to humans. Carbon content in carbonized fibers is up to 90%. Carbonized fibers have good chemical resistance, they are functional in almost all environments, except for highly concentrated acids, including: nitric (Nitric), orthophosphoric (Orthophosphoric), sulfuric (Sulfuric), sulfurous (Sulfurous), hydrochloric (Hydrochloric), oxalic (Oxalic) ) and in other environments, the pH value of which is less than 2, i.e. pH

Carbon carbon fibers

To obtain high-modulus carbon fiber, carbonized fibers are subjected to heat treatment at a temperature of about +2500°C. Carbon fiber is used to produce special yarn of increased strength, which is used for the production of special items and products. One of the main values ​​characterizing carbon (carbon) yarn is the coefficient k, which expresses the number of elementary continuous fibers in the yarn. 1k=1000 fibers. The most common fibers are 1k, 3k, 6k, 12, 24k and 48k are also used. The k coefficient is used to denote only carbon fibers; the properties and characteristics of general purpose carbonized fibers are described by other parameters.

One of the main products made from high modulus carbon fiber is structural carbon fabric. Carbon (carbon) fabrics are used to reinforce composite materials in the production of carbon fiber reinforced plastics. Carbon fiber plastics based on resins and carbon fabric are highly resistant to corrosion and various types of deformation, allowing the production of highly complex products with a practically zero linear expansion coefficient. Carbon fiber reinforced plastics reduce the weight of the structure by an average of 30%. In addition, carbon fiber is a conductive material.
In addition to fabrics, special tapes, cords, paper and other products for many industries are made from high-modulus carbon fibers.

Carbonized carbon fabric RK-300

Carbonized carbon fabric RK-300 is used as high temperature insulation. It is an excellent thermal protection in a variety of industrial applications and can be used as a cushioning material or as a winding, as well as in the form of protective screens and curtains.

Carbonized fabric RK-300 is a modern substitute for fiberglass and other heat-insulating fabrics, including asbestos. Unlike fiberglass, carbonized fabric does not irritate the mucous membranes of the respiratory tract and does not cause itching of the skin. Compared to asbestos fabric, carbonized fabric RK-300 is completely safe for humans; in addition, it has an incomparably longer service life, excellent chemical resistance and the possibility of repeated use due to its unique properties.

Options:

Blade width: 1000mm

Thickness: 1.6mm ~ 5.0mm

Density: 520~560 g/m²

Weave: plain

Attention: Dear colleagues, dear partners! All carbonized carbon fiber products and products can be made from high strength and high modulus carbon fiber. Also, upon request, it is possible to produce thermal insulating fabric RK-300 from high-modulus carbon fiber - fabric RK-300H. Parameters of RK-300H carbon fiber fabric. Blade width: 1000mm~1500mm; Thickness: 1.0mm~6.0mm; Density: g/m? depending on thickness; Operating temperature: -100°С +1200°С

Carbonized Carbon Fabric with Single Side Aluminum Coating RK-300AF

Carbon carbonized fabric RK-300AF is a modern, highly reliable industrial thermal insulation. An excellent substitute for fiberglass and asbestos fabrics. Unlike fiberglass and asbestos fabrics, carbonized fabric is completely harmless.

One-sided application of aluminum to carbonized fabric gives it even better thermal insulation properties. The aluminum layer on the fabric is a thermal screen that reflects high temperature if the fabric is used as a thermal curtain. At the same time, when using RK-300AF as a winding thermal insulation material, the aluminum layer ensures maintaining a stable temperature inside the insulated system.

Options:

Blade width: 1000mm

Thickness: 1.6mm ~ 5.0mm

Density: 520~560gsm?

Operating temperature: -100°С +450°С

Weave: plain

Attention: Textile RK-300HAF

Carbonized Carbon Tape

Thermal insulation tapes made of carbonized carbon fiber are an excellent, modern replacement for asbestos tapes and glass tapes. Carbon tapes are significantly superior to asbestos tapes and fiberglass tapes in terms of physical and mechanical properties, and also have a wider range of chemical resistance. In addition, carbonized tapes are completely safe for humans and environmentally friendly. Carbon carbonized tapes are used for thermal insulation of cable trunks, elements of instruments and machines, pipelines and other systems and equipment operating at temperatures up to +450°C.

We produce 2 types of carbonized carbon tapes:

RK-300T tape is a carbonized carbon tape without coating.

RK-300TAF tape is a carbonized carbon tape with a thin aluminum layer applied on one side.

Options:

• Blade width: 5.0mm ~ 1000mm
• Thickness: 1.6mm ~ 5.0mm
• Density: 520~560gsm?
• Operating temperature: -100°С +450°С
• Weave: plain

Ribbons RK-300THAF and RK-300TH made of high strength and high modulus carbon fiber. Operating temperature: -100°C +1200°C.

Carbon cord, braided RK-300RS

Carbon cords are made from both general purpose carbonized carbon fiber and high modulus carbon carbon fiber. The cords are made with both round and square cross-sections using the weaving method. Carbon cords can be made using the through braiding method, as well as using single-layer or multi-layer core braiding. In the production of cords, to obtain the required properties of the final product, together with carbon yarn, other types of yarn can be used, including ceramic, aramid, and fiberglass yarn.

Carbon cords are used as fireproof, heat-resistant and heat-resistant seals in many industrial applications. Carbon cords are significantly superior to similar products made from other types of fibers in almost all physical, mechanical and technical indicators; in addition, cords made from high-modulus carbon fiber are completely chemically inert, their acid pH index is in the range of 0~14, which allows their use in environments any concentrated acids and alkalis.

Also, unlike fiberglass cords, which emit fine glass dust that irritates the mucous membranes of the eyes, sinuses, palate and causes itching of the skin, carbon cords are completely harmless. The breaking load of high modulus fiber carbon cords is by far the best.

Carbon cords also serve as the basis for the production of gland packings with unique properties for use in almost all types of industry.

Options:

• Working temperature: +280°C~+1200°C
• Section sizes: O4mm ~ O50.0mm and 4.0mmx4.0mm to 70.0mmx70.0mm

Carbon construction fabrics

Structural carbon fabrics are made from high modulus carbon fiber yarns. In the production of carbon construction fabrics, yarns with a coefficient of 1k, 3k, 6k, 12, 24k and 48k are used, where k is the number of elementary continuous fibers in the yarn. 1k=1000 fibers.

The main area of ​​application of high-modulus carbon fiber fabrics is as a reinforcing layer in the production of heat-shielding, chemically resistant composite materials, as well as fillers in the production of carbon fiber plastics.

Carbon fiber fabrics are made of different types of weaving, depending on their further purpose of use. There are three main types of weaving carbon fabrics:

• The most common weave is plain weave, it is described as follows: 1/1. In plain weaving, each warp thread is intertwined with a weft thread, one after another. This type of weaving provides the best strength to the fabric.
• Satin weave fabric. This weaving method is described as follows: 4/1, 5/1 - 1 weft thread overlaps 4, 5 warp threads. Fabrics made using the satin weave method are the least durable, so these fabrics are made very dense. Since the warp and weft threads rarely bend in satin weaving, the surface of such fabrics is even and smooth.
• Twill or twill weaving method. This type of weaving is described as follows: 2/1, 2/2, 3/1, 3/2... - the number of warp threads covered by the number of weft threads. Twill weaving is visually easily identified by oblique stripes on the surface of the fabric.

The table below shows the main characteristics of standard carbon fabrics. The carbon fiber for these fabrics is derived from polyacrylonitrile (PAN) fibers.

Fabric brand	Carbon content	Elastic modulus E, GPa	Elongation, %	Linear density, g/1000m	Density, g/cm?
RK-301	98,5	3800	210	1,5	100	1,76
RK-303	98,5	3900	215	1,6	187	1,76
RK-306	98,5	3600	206	1,5	360	1,76
RK-312	98,5	3400	209	1,6	729	1,76

E- Young's modulus or modulus of elasticity - a coefficient characterizing the resistance of a material to tension and compression during elastic deformation. For clarity, we add that the modulus of elasticity E for steel is from 195 GPa to 205 GPa, and for fiberglass from 95 GPa to 100 GPa. The elastic modulus of graphitized carbon fiber is up to 677 GPa, while tungsten wire has an E coefficient of 420 GPa.

Parameters of standard structural carbon fiber fabrics:

• Width: 1000mm ~2000mm. The maximum width upon request is 2000mm.
• Thickness: 0.25mm~3.0mm
• Density: 100g/m?~640g/m?
• Blade width: 1000mm
• Temperature: up to +1200°С
• Carbon content: >98.5%

It is possible to produce carbon fiber fabrics with non-standard parameters.

Winding length per roll - upon request. The fabric is packed in film and cardboard boxes.

Brands of carbon fabrics and their designation

All carbon fabrics produced by enterprises of the IFI Technical Production holding have the letters RK in their name, denoting the manufacturer's trademark RK™ and the index 300. For example, carbon carbon construction fabric made from 6k yarn, that is, from yarn containing 6000 continuous fibers, has designation RK-306. Carbon fabric made from 3k or 12k yarn, RK-303 and RK-312 respectively.

Application for the supply of carbon fabrics

Dear Colleagues! You can purchase carbon fabrics in any way convenient for you. We offer the following options:

• Purchase of products directly from the factory in China. You enter into a direct contract with the factory and work independently. To do this, you need to send a request to the following address: This e-mail address is being protected from spambots. You must have JavaScript enabled to view it. We will send you contact information, including the phone number and email address of the factory employee responsible for export.
• Purchase of products through the Russian representative office of the IFI Technical Production holding, through the Rus-Kit company. The transaction is carried out under a supply agreement concluded between your organization and the Rus-Kit company. In this case, Rus-Kit takes upon itself all issues regarding the organization of delivery and customs clearance of goods. To do this, you also need to send a request to the email address: This e-mail address is being protected from spambots. You need JavaScript enabled to view it

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Currently, a large number of carbon fibers, varied in purpose, composition and properties, have been developed and industrialized. The branded assortment is based primarily on the type of initial fiber when obtaining carbon, the purity of raw materials, processing technology of the initial fibers, the final processing temperature (which determines the perfection of the structure of the carbon and its properties), the required texture of industrial forms of carbon and their purpose. The assortment of carbon fibers is quite wide and varied , which is determined by the type and composition of the feedstock, its ability to undergo thermal transformations when heated, and the conditions (regimes, environment) for carrying out thermal transformations when producing carbon fibers. Based on elementary carbon fibers, various textile forms are obtained, which are used as carbon fiber materials (CFM) as components for the production of composite materials or as independent materials (products). The brand range of carbon fiber materials is determined primarily by the purpose and need for this type of material for modern technology products. Companies producing carbon fibers, as a rule, specialize in the production of several types of carbon fiber materials, but on one type of feedstock. For example, the companies Hercules, UCC, Celanese, HITOCO, Great Lakes Carbon, Stackpole Carbon Fibers (USA) produce CFM based on PAN fibers; Tore, Toho Besoon, Nihon Kabon, Asahi Nihon Kabon faiba, Mitsubishi Reyon, Sumitomo Kagaku (Japan). The Union Carbite company produces CFM based on PAN, GC and pitches. CFM based on conventional pitches is produced by Kureha Kagaku (Japan), Courtlands (Great Britain), and Serofim (France).

Properties of carbon fibers

The properties of carbon fiber reinforced plastics depend on the properties of carbon fibers, which in turn are determined by the conditions of pyrolysis of organic fibers (cellulose hydrate, polyacrylonitrile, fibers from mesophase pitches) currently used as raw materials for the manufacture of carbon fibers.

Mechanical properties. The tensile modulus of elasticity (along the fibers) of high-quality high-strength carbon fibers (based on PAN) is 200 - 250 GPa, high-modulus type (based on PAN) - about 400 GPa, and carbon fibers based on liquid crystalline pitches: 400 - 700 GPa. At the same heating temperature, carbon fibers based on liquid crystal pitches have a higher tensile modulus of elasticity than fibers based on PAN. The tensile modulus across the fibers (flexural stiffness modulus) decreases as the tensile modulus along the fibers increases. For PAN-based carbon fibers it is higher than for fibers based on liquid crystal pitches. The transverse modulus of elasticity is also affected by the orientation of the atomic planes in the carbon fiber cross-section. The axial tensile strength of high-strength PAN-based carbon fibers is 3.0-3.5 GPa, high elongation fibers are ~4.5 GPa, and high-modulus fibers are 2.0-2.5 GPa. High-temperature processing of the second type of fiber produces high-modulus fibers with a tensile strength of approximately 3 GPa. The strength of fibers based on liquid crystal pitches is usually 2.0 GPa. The theoretical value of the tensile strength of graphite crystals in the direction of the atomic lattice planes is 180 GPa. The experimentally measured tensile strength of high-strength and high-modulus PAN-based carbon fibers in a section 0.1 mm long is 9-10 GPa. This value is 1/20 of the theoretical value and 1/2 of the strength of filamentary graphite single crystals. For carbon fibers based on liquid crystalline pitches, the strength measured in a similar way is 7 GPa. Tables 17.1, 17.2 show the mechanical properties of the most common carbon fibers.

The lower strength of industrially produced carbon fibers is due to the fact that they are not single crystals and there are significant deviations from regularity in their microscopic structure. The properties of carbon fibers can be significantly improved up to a breaking elongation of 2% and a strength of 5 GPa and above.

Table 17.1 - Mechanical properties of carbon fiber.

Characteristic	CF based on PAN			HC based liquid crystalline pitches
	high strength	high elongation	highly modular
Fiber diameter, nm
Tensile modulus of elasticity, GPa
Breaking tensile stress, GPa
Tensile elongation, %
Density, g/cm3
Specific strength, m

Table 17.2 - Physical and mechanical properties of carbon fibers.

Original fiber	Diameter, µm	Density, g/cm 3	Breaking tensile stress, MPa	Tensile modulus of elasticity, E, GPa	Testile form
Polyacrylonitrile					Continuous tourniquet
Viscose					Continuous tourniquet

As can be seen from the tables, carbon fibers have low density and high tensile strength and elastic modulus. Consequently, carbon fibers have high strength and specific elastic modulus. The most characteristic feature of carbon fibers is their high specific modulus of elasticity. This makes it possible to successfully use carbon fibers for reinforcing materials for structural purposes. Comparing high-modulus fibers with low-modulus fibers of similar chemical composition, it should be noted that with an increase in the elastic modulus and density of carbon fibers, the volume of closed pores, the average diameter and specific surface area decrease, and its electrical conductivity improves.

Electrical properties. The increase in elastic modulus as the texture angle decreases means that the structure of carbon fiber approaches that of graphite, which has metallic conductivity in the direction of the hexagonal layer. Carbon fibers obtained at temperatures not lower than 1000°C have high electrical conductivity (more than 102 Ohm -1 -cm -1). By varying the elastic modulus, and therefore the electrical properties of the carbon filler, it is possible to regulate the electrical properties of the composite material. In the process of converting organic fibers into carbon fibers, a transition occurs through all conduction bands. The original fibers are dielectrics; during carbonization, the electrical resistance sharply decreases, then with an increase in the processing temperature above 1000 o C, although it continues to decrease, it is less intense. Carbonized fibers are classified as semiconductors by type of conductivity, while graphitized fibers cover the range from semiconductors to conductors, approaching the latter as the processing temperature increases. For carbon fibers, the temperature dependence of conductivity is determined by the final temperature of their processing, and, consequently, by the electron concentration and crystallite sizes.

It should be noted that the higher the carbonization temperature, the lower the temperature coefficient of electrical conductivity. Carbon fibers have hole and electronic conductivity. With increasing temperature treatment, accompanied by an improvement in the structure and an increase in the number of electrons, the conduction band gap decreases, therefore the electrical conductivity increases, which for fibers treated at high temperatures approaches the electrical conductivity of conductors in absolute value.

Thermal properties. One of the manifestations of the features of the anisotropic structure of high-modulus carbon fibers is a negative coefficient of thermal linear expansion along the fiber axis, which increases the level of residual stresses in high-modulus fibers. For fiber with a large elastic modulus, the coefficient is higher in absolute value and has a negative value over a wider temperature range. Thus, for carbon fibers made from PAN fiber (Figure 17.11), the maximum (in absolute value) value of the coefficient is observed at 0°C, and with increasing temperature its sign changes to the opposite (at temperatures above 360°C for fiber with E= 380 GPa and above 220 °C for fiber with E= 280 GPa. It should be noted that the curve in Figure 3.11 coincides well with a similar dependence of the coefficient of thermal expansion of the pyrolytic graphite lattice along the axis A.

Due to their high C-C bond energy, carbon fibers remain solid at very high temperatures, giving the composite material high temperature resistance. Short-term tensile strength of high modulus fiber containing 99.7 wt. % carbon remains virtually unchanged in neutral and reducing environments up to 2200 °C. It does not change at low temperatures either. In an oxidizing environment, the strength of carbon fiber remains unchanged up to 450°C. The surface of the fiber is protected from oxidation by oxygen-resistant protective coatings made of refractory compounds or heat-resistant binders; Pyrolytic coatings are most widely used.

Figure 17.11 - Dependence of the coefficient of thermal linear expansion

along the grain for carbon fibers with a modulus of elasticity of 380 (1)

and 280 GPa (2) from temperature..

Chemical properties. Carbon fibers differ from other fillers in their chemical inertness. The chemical resistance of carbon fibers depends on the final processing temperature, the structure and surface of the fiber, and the type and purity of the feedstock. After exposure of high-modulus fibers obtained from PAN fiber to aggressive liquids for 257 days at room temperature, a noticeable decrease in tensile strength is observed only under the action of orthophosphoric, nitric and sulfuric acids (Table 17.3).

Table 17.3 - Chemical resistance in aggressive environments of high-modulus hydrocarbons based on PAN (duration of exposure 257 days).

Reagents	Temperature, °C	Diameter fibers, nm	σ R , MPa	E R , GPa
Control fiber sample
Acid (50%):
Coal
Orthophosphoric
Vinegar ice
Sodium hydroxide solution,

The elastic modulus of the samples changes only under the influence of a 50% nitric acid solution. The strength of alkaline glass fiber after exposure for 240 hours in 5% solutions of sulfuric or nitric acids decreases by 41 and 39%, respectively. As the temperature increases, the resistance of carbon fiber to aggressive environments decreases.

It oxidizes especially easily in solutions of nitric acid. A solution of sodium hydrochloride oxidizes carbon, as a result of which the diameter of the fiber decreases, and its mechanical properties even improve somewhat.

According to the degree of activity in relation to high-modulus carbon fiber obtained from PAN fiber, acids can be arranged in the following series: HNO 3 > H 2 S0 4 > H 3 P0 4 > HC1. Acetic and formic acids and alkali solutions of any concentration and at any temperature do not destroy carbon fibers. The chemical resistance of carbon fibers ensures the stability of the properties of composite materials based on them.

Defects and wetting. Pyrolysis of organic fibers is accompanied by an increase in their porosity. High-modulus carbon fibers have elongated pores and differ from low-modulus carbon fibers in the orientation of grooves and cracks along the fiber axis and their lower concentration on the surface. Apparently, during drawing, some surface defects are smoothed out, which is especially effective during high-temperature processing of fibers. The pores on the surface of carbon fibers have different sizes. Large pores with a diameter of several hundred angstroms are filled with a binder during the molding of a composite material, and the adhesion strength of the binder to the filler increases. Most of the pores on the surface of the fibers have a diameter of several tens of angstroms. Only low-molecular components of the binder can penetrate into such small cavities, and a molecular sieve redistribution of the binder occurs at the surface of the filler, changing its composition.

The wettability of fibers by the binders used to produce carbon fiber plastics has a great influence on their properties. Unlike glass fibers, the surface energy of carbon fibers is very low, so the fibers are poorly wetted by binders, and carbon fiber reinforced plastics are characterized by low adhesion strength between the filler and the binder. The adhesion strength of the fibers to the binder increases if a thin layer of monomer is first applied to the surface of the fibers, wetting it well and filling all the pores. As a result of polymerization of the monomer, the fiber is covered with a thin layer of polymer - a protector, “sealing” its surface defects. Then the filler is combined with the selected binder, the product is molded and the plastic is cured according to the standard regime.

Currently, several more methods have been proposed to increase the adhesion strength of carbon fiber to the binder, the effectiveness of which is assessed by increasing the shear strength of the composite material:

Removing the lubricant film from the surface of carbon fibers after textile processing;

Etching the surface of carbon fibers with oxidizing agents;

Finishing of carbon fibers;

Growing whisker-like crystals with high shear resistance on the surface of fibers (vorserization or visceration).

In some cases, several processing methods are used sequentially.

Worshiping high-modulus carbon fibers is the most radical method of increasing the shear strength of carbon fiber reinforced plastics. Proportional to the volume content of whiskers on the fiber, not only the shear strength increases, but also the compressive and bending strength in the transverse direction due to additional strengthening of the matrix with crystals with high mechanical properties (for example, the strength of ?-SiC whiskers is 7-20 GPa at modulus elasticity about 50 GPa). With a high content of whiskers on the fiber (more than 4-7%), the strength and elastic properties of the plastic deteriorate. In some cases, the decrease in plastic strength is associated with the loss of strength of carbon fiber during vorserization. Table 17.4 shows how the properties of carbon fiber reinforced plastics depend on the method of preparing the carbon fiber surface.

Table 17.4 - Effect of various types of surface preparation of high modulus fiber on the properties of unidirectional epoxy carbon fiber reinforced plastic.

Method for preparing the surface of carbon fibers	Density, g/cm 3	Breaking stress, MPa, at		Modulus of elasticity, GPa
		shift	bend
Fiber with lubricant
Etching in HNO 3
Burning off the lubricant in nitrogen and impregnating with epoxy resin
Worserization silicon carbide whiskers

The ability of carbon fibers containing the same amount of carbon (at least 99 wt.%) to vorserization from the gas phase increases with a decrease in its resistance to oxidation, which is proportional to the concentration of surface defects.

Physical properties carbon fibers depend on their background (carbonization and graphitization conditions), and some indicators on the nature and quality of the raw materials. Many of the properties of carbon fibers are determined by the final processing temperature, but other factors may also make significant contributions. Table 17.5 shows the most typical physical properties of carbon fibers.

The density of graphite is 2.26 g/cm 3, it significantly exceeds the density of carbon fiber, which is due to the less perfect structure of the latter. Among heat-resistant fibers, carbon has the lowest density; this has a beneficial effect on the specific mechanical properties of the fiber. Graphite fibers have a small specific surface area.

Table 17.5 - Physical properties of carbon fibers.

Characteristic	Fiber
	carbonated	graphitized
Density, kg/m 3
Specific surface area, m 2 /g
Temperature coefficient of linear expansion, 10 6 / K
Specific heat capacity, kJ/kg K
Thermal conductivity, W/(m K)
Electrical resistivity, 10 -5 ohm m
Dielectric loss tangent (at 10 10 Hz)
Hygroscopicity,%

The specific surface area of ​​carbonized fibers, depending on the conditions of their production and the type of raw materials used, can vary within wide limits.

In order to increase the specific surface area of ​​500-1000 m 2 /g, carbon fibers are treated with superheated water steam, carbon dioxide and other reagents. Carbon fibers are characterized by a small coefficient of linear expansion, noticeably lower than metals, graphite and quartz glass. In terms of heat capacity, carbon fibers differ little from other solids. A characteristic feature of carbon and especially graphitized fibers is their very high thermal conductivity. This is also characteristic of graphite. When using carbon fibers or compositions based on them as heat-shielding materials, high thermal conductivity is undesirable, since intense heat transfer occurs through the composite material. To eliminate this drawback, in addition to carbon fiber, other heat-resistant fibers are added to composite materials, in particular, metal oxide fibers with low thermal conductivity.

Carbon fibers with a developed specific surface area are highly hygroscopic due to water condensation in the pores. Graphite fiber has low porosity, so its hygroscopicity is low. Hygroscopicity is of great importance in the manufacture of composite materials.

Textile forms of carbon fibers

Carbon fibers can be produced in a wide variety of textile structures: stapled, continuous filament, woven or non-woven. Tows, yarns, rovings and non-woven scrims are the most common types of carbon fiber structures currently used. Carbon fibers have a high modulus of elasticity and low elongation. Therefore, they cannot withstand repeated deformation and their use for producing woven materials presents certain difficulties. However, due to progress in carbon fiber production technology and weaving techniques, it has become possible to make all kinds of woven materials from them.

The advantage of unidirectional fabrics (in this case, thin threads: glass or organic, located along the weft, serve only for the technological connection of threads or strands with each other) is that they practically eliminate kinks of fibers in the longitudinal direction, the fibers are well oriented, the material is obtained smooth and pleasant to the touch. They are also produced in the form of hybrid tapes and fabric in combination with fiberglass threads. Currently, the range of fabrics is very diverse; they differ in the density of the threads along the width, the weaving structure, the ratio of the number of threads in the longitudinal (along the warp) and transverse (along the weft) directions, the number of elementary fibers in the bundle and other characteristics.

Depending on the conditions of use, CFM is produced in the form of continuous threads and strands (formed from 1000, 3000, 5000, 6000, 10000 and more elementary continuous fibers), cords, staple fiber, knop, tapes, fabrics (often combined with polymer or glass fibers), unidirectional tapes in which strong warp threads are bound with low-strength weft, non-woven materials (felt, mats), etc. Almost the entire possible range of textile forms has been developed and used based on carbon fibers.

To obtain woven products from carbon fiber, two main methods are used: weaving of initial fibers and subsequent thermal processing of woven products into carbon ones (i.e. carbonization and graphitization of woven forms); production of carbon threads, tows and their subsequent textile processing. The advantage of the latter method is the possibility of obtaining fabrics with less anisotropy of properties, as well as the possibility of obtaining combined woven materials from CF and other types of fibers; the disadvantage is the fragility of CF and the associated difficulties during textile processing.

Figure 17.12 shows the types of some special purpose fabrics: uncrimped fabric, in which, by eliminating the bending of the carbon fibers, damage to the fibers and loss of strength are prevented; spiral fabric, in which carbon fibers are arranged in a spiral and interconnected in a radial direction; fabrics with carbon fiber orientation at an angle of 0.30 and 60°; three-dimensional fabrics in which the carbon fibers are also oriented in the direction of the fabric thickness, etc.

a - uncrimped fabric; b - spiral fabric; c - fabric with triaxial orientation of threads in the plane of the fabric; d - three-dimensional fabric with orthogonal volumetric orientation of threads.

1 - glass thread; 2 - carbon thread.

Figure 17.12 - Examples of special purpose fabrics.

Carbon fiber fabrics. The properties and conditions for producing carbon fabrics depend on the structure of these fabrics, the density of the weave, the crimp of the yarn, the density of the original yarn and the weaving conditions.

The density of threads in the warp and weft is determined by the number of threads in 1 cm of fabric, respectively, in the longitudinal and transverse directions. The “warp” is the yarn placed along the length of the fabric, and the “weft” intertwines the fabric in the transverse direction. Therefore, the density of the fabric, its thickness and tensile strength are proportional to the number of threads and the type of yarn used in weaving. These parameters can be determined if the fabric design is known. There are different types of warp and weft weaves to create durable fabrics. By varying the type of fabric, it is possible to create a variety of reinforcing structures that, to a certain extent, affect the properties of composites made from them. In some cases, the use of carbon fabrics requires special types of weaves.

Braid is a narrow (less than 30.5 cm wide) fabric that may contain a loose selvedge (i.e., fill yarn extending beyond the tape). Carbon fiber webbing in the form of braided sleeves is characterized by greater flexibility compared to carbon fiber-based fabrics. From braid you can produce products of complex configurations with an irregularly shaped surface, etc.

Textile Carbon Fiber Yarn- These are single parallelized fibers or strands (bundles) collected together, which can later be processed into textile material. Continuous single tows (strands) are the simplest form of textile carbon fiber yarn, known as “plain yarn”. To use such yarn in further textile processing, it is usually subjected to slight twisting (less than 40 m -1). However, for a large number of fabrics, thicker yarn is needed. This range of textile yarns can be produced by twisting and caning. A typical example is the twisting of two or more simple strands together with simultaneous reweaving (i.e., subsequent twisting of two or more pre-twisted strands).

As a result of the operations of twisting and twisting, yarn is obtained, the strength, flexibility and diameter of which can vary. This is an important prerequisite for the creation of various fabrics from which composites are subsequently obtained.

Harnesses consist of a large number of filaments collected in a bundle. Typically, tows with a number of filaments of 400, 10 thousand or 160 thousand are used. Yarn is usually understood as twisted threads consisting of cut fibers, while roving is a strand (strand) consisting of parallel or slightly twisted bundles of fibers. Finally mats (tapes) Consist of a large number (sometimes up to 300) of carbon fiber bundles or strands laid side by side or stitched together and can be processed into various types of textile structures. Short carbon fibers (3 - 6 mm long) can be processed into felt or non-woven fabric using conventional technology.

For carbon fiber and carbon fiber composites, carbon fibers UKN-P/2500, UKN-P/5000 with surface treatment and the number of filaments in the thread are respectively 2500 and 5000, VMN-4, VMN-RK, Rovilon, VEN-280, UKN/5000, UKN /10000, Coulomb/5000A, Coulomb/5000B with a linear density from 200 to 900 tex, characterized by strength and elastic modulus within a fairly wide range. The properties of some carbon filaments are presented in Tables 17.6 and 17.7.

Table 17.6 - Properties of carbon filaments.

Indicators	Filler brand
	UKN-P/2500	UKN- P/5000	UKN/ 5000	UKN/ 10000	Pendant/5000A Pendant/5000B
Linear density, tex
Deviation of linear density,%
Relative breaking load of thread when broken by a loop, n/tex
Mass fraction of sizing agent, %
Modulus of elasticity, GPa
Breaking tensile stress of a thread in microplastic, GPa
Breaking stress of plastic, GPa at: Stretching

Table 17.7 - Properties of carbon filaments.

Indicators properties	Filler brand
	VMN-4	VMN-RK-3	ROVILON			VEN-280-1	VEN-280
Linear density, tex
Deviation of linear density, % no more
Thread density, g/cm 3
Breaking tensile stress of a filament, GPa
Modulus of elasticity of the rope in plastic, GPa
Dynamic modulus of elasticity of the rope, GPa
Bending strength of a rope in plastic MPa

The most widely used as a reinforcing filler for carbon fiber laminates are carbon tapes of the LU-P and ELUR-P types, which are rolls 250 mm wide tightly wound on double-flange reels. The main characteristics of the tapes are presented in Table 17.8. A distinctive feature of carbon tapes is their low linear density, which ensures the production of carbon fiber plastics with a monolayer thickness of 0.08-0.13 microns.

Table 17.8 - Properties of carbon tapes.

Tape type	Tape width, mm	Linear density, g/m	Thread density, g/cm 3	Number of threads per 10 cm, no less	Breaking tensile stress in carbon fiber reinforced plastic, GPa, not less	Breaking stress during compression in carbon fiber reinforced plastic, GPa, no less	Modulus of elasticity in bending, GPa	Volume fraction of filler in carbon fiber, %	Density of carbon fiber, g/cm 3	Carbon fiber monolayer thickness, mm

A large group of carbon reinforcing fillers are woven materials based on carbon threads UKN-P/2500 and UKN/P500. These are woven tapes UOL-1 and UOL-2 with a width of 300, 460 and 600 mm. (In the symbol of the tape, the first number is the width of the tape, the second number in the marking is the type of threads used as the warp: 1- for UKN-P/5000 threads and 2- for UKN-P/2500 threads.) These tapes have only carbon threads in the warp and in the weft, the tapes have sparse glass or organic threads with a linear density of 14-30 tex. They are produced on tape weaving looms.

To expand the range, combined tapes of the UOL-K type are produced with a 6:1 ratio of carbon and glass threads. The main characteristics of woven carbon and composite tapes are given in Table 3.9. Unlike carbon fibers of the LU type, these fillers provide carbon fiber reinforced plastics with a higher monolayer thickness from 0.17 mm to 0.25 mm and a higher level of strength characteristics. Woven tapes of the LZHU type, unlike tapes of the UOL type, are woven using raw materials and have a carbon weft thread. LZHU tapes differ in linear density when using different carbon threads in the base of 2500 or 5000 filaments. The main characteristics of these tapes are presented in Table 4.9.

The carbon fabric UT-900-2.5 based on UKN-P/2500 threads woven with a twill weave, which ensures an equal density of warp and weft threads, is fundamentally different from the previously discussed fillers. The characteristics and properties of fabrics are given in table 17.9.

Table 17.9 - Properties of woven carbon tapes and fabrics.

The brand range and properties of domestic and foreign CFM are presented in tables 17.10 - 17.13.

Table 17.13 presents some properties of foreign carbon fibers from various parent fibers. They can be delivered to the consumer after or without surface treatment. The type and type of textile structure for processing carbon fibers is usually determined by its application in the composite material. This also determines the method of producing the composite: laying, injection molding or pultrusion.

Volumetric structures based on carbon fibers.

One of the main advantages of reinforced composite materials is the high specific strength in the direction of reinforcement. Another important advantage of such materials over isotropic materials is the effective control of the anisotropy of mechanical, thermophysical and other properties in the direction of reinforcement. The anisotropy of properties is controlled by varying the placement of reinforcement.

Table 17.10 - Carbon fillers for structural carbon fiber reinforced plastics (Russia).

	Textile	Density g/cm 3
LU-P-0.1 and O.2 4 , 5
UKN-P-O,1 1 ,4, 5
UKN-P-5000M 4, 5
UKN-P-5000 2, 6
UKN-P-2500 4, 5
PENDANT N24-P 5
GRANITE P 5	thread 400 tex
ELUR-P-0.1 4 , 5	tape245±30mm
	tape 90+10 mm
	tape 90±10 mm
	tape,?= 0.235±0.015
	tape, ?= 0.175+0.015
	twill, ?= 0.22±0.02
ELUR-P-0.08 4 , 5
	thread, tourniquet
	thread, tourniquet

Note: 1 - analogue of Tornel 300, Toreyka TZOO; 2 - based on UKN-P-5000, carbon-organic tapes UOL-55, 150, 300, 300-1, ZOOK (NPO "Khimvolokno"); UOL-300-1 (warp UKN-P-5000, 410 tex, weft SVMK 14.3 tex); UOL-ZOOK (warp UKN-P-5000, 410 tex and Armos 167 tex, weft SVMK 14.3 tex); UOL-150, 300 (warp UKM-P-5000, 390 tex, weft SVMK tex 29.4); 3 - warp and weft made of UKN-P-2500 200 tex, selvedge Ural N 205 tex; 4 - PAN threads for ELUR-P, LU-P tex 33.3, UKN-P-5000 tex 850, UKN-P-2500 tex 425; 5 - P - electrochemical oxidation (ECHO method); 6 - used for the manufacture of TZ-structures such as TsOO and TsTMZ; Tex is the mass of 1 km of fiber in grams.

Table 17.11 - Properties of carbon materials based on viscose (hydrated cellulose, HC) fibers, for thermal protection, adsorption-active materials, electrical products (heaters). (Russia) .

Brand material	Textile form	%	Breaking load per strip 5cm, kgf		Elemental Strength threads, GPa
	fabric, ribbon
Ural TR Z/2-15	Knitwear
Ural TR 3/2-22	Knitwear
Ural TM/4-22	Multilayer fabric
Ural LO-22	Unidirectional tape
Ural LO-15	Unidirectional tape
	textile thread
	sewing thread
Ural Tr-3/2-15E	surface-treated knitwear
Uglen, Uglen-9

Table 17.12 - Textile forms and properties of carbon tows (Russia).

Options	Carbon strands, grades
	VMN-4	ROVILON	VPR-19(s)	VNV(s)
Feedstock		Nitron 650 -1700 tex	Nitron 850 -1700 tex
Number of threads, pcs
Number of twists per 1 m
Number of fibers (filaments), pcs.
Length, max, m
Diameter, max, µm
Pyrolysis temperature, Max, °C
Density, g/cm 3
Tensile strength, ?, GPa
Tensile modulus of elasticity, E, GPa
Relative elongation, ε, %
Lubricant

Table 17.13 - Properties of foreign industrial carbon fibers.

Fiber	Supplier company	Source material	σ IN , MPa	E, GPa	 , kg/m 3	σ , 10 -4 cm/m	 etc , W/ (m  °C)	α etc , TO -1
Fortafil 3 (0)
Fortafil 5
CI - Tex 12000
CI - Tex 6000
HI - Tex 3000
Hi-Tex 1500
Panex 1/4 CF-30
Panex 30 R
Panex 30V800d
Selion GY-70
Selion 6000
Selion 3000
Selion 1000
Thornel 300 WYP 90 - 1/0
Tornel 300 WYP30-1/0

Names of companies: G - “Hercules” (Hercules), GLK - “Great Lakes Carbon” (Great Lakes Carbon), K - “Carborundum” (Carborundum), P - “Polycarbon” (Polycarbon), SF - “Stackpole Carbon Fibers” (Stackpole Carbon Fibers), C - “Celanese”, YK - “Union Carbide”.

The reinforcing elements of carbon composite materials are carbon fibers. Reinforcing structures have been developed that have three, four, five or more directions of reinforcement. By changing the ratio of reinforcement in different directions, materials with specified properties are created.

There are several systems of reinforcement structures for composite materials. In practice, systems of two, three and n threads

A characteristic feature of materials formed by a system of two threads is the presence of a given degree of curvature of the fibers in the warp direction (x-axis), while the weft fibers (y-axis) are straight. There is no reinforcement in the third direction (z axis). The main reinforcing parameters of this group of materials are the degree of curvature of the base fibers (angle ) and the reinforcement coefficient  in the direction of the warp and weft (Figure 17.13).

Figure 17.13 - Variants of reinforcement schemes formed by a system of two threads. Connecting adjacent layers with directional fibers at: in plane zx(A) and in the plane zy(b); throughout the entire thickness of the structure and in the plane zx(V) and in the plane zy(G). Connection through two layers using in the direction X straight fibers ( d) and through the layer and throughout the entire thickness of the material using in the direction X straight fibers ( e). Connection through a layer with variable density along the thickness of the material ( and) .

Composite materials formed by a system of three threads have reinforcement in three directions of selected coordinate axes. The most common reinforcement schemes are shown in Figure 17.14.

Reinforcement schemes, as a rule, are formed by mutually orthogonal fibers (Figure 17.14, a, b), however, there are schemes with an oblique arrangement of fibers (Figure 17.14, c, d). Reinforcing fibers can be straight (Figure 17.14, A), have a given degree of fiber curvature in one (Figure 17.14, V) or two (Figure 17.14, G) directions. The number of fibers and the spacing between them in each of the three directions are the main parameters of composite materials, which are determined by the conditions of their use.

Figure 17.14 - Options for reinforcement schemes formed by a three-strand system

with straight fibers in three directions ( a, b),

with straight fibers in two directions ( V),

with a given degree of fiber direction in two directions ( e) .

The four-strand system makes it possible to obtain composite materials with different options for the spatial arrangement of reinforcement. Option 4 is the most popular d. Its characteristic feature is the location of the reinforcement along the four diagonals of the cube. This laying scheme, with equal distribution of reinforcement along the reinforcement directions, makes it possible to obtain an equilibrium structure.

Reinforcement of composite materials formed by a system of multiple threads is carried out in different directions, most often in three mutually perpendicular directions of the selected coordinate axes and in diagonal planes containing the coordinate axes. More complex reinforcement schemes are also possible (Figure 17.15). The geometry of spatial reinforcement is created based on the conditions of destruction of the material and should provide targeted anisotropy of properties. An increase in the number of reinforcement directions helps to reduce the anisotropy of properties, the overall reinforcement coefficient, and, consequently, the absolute values ​​of the material characteristics. Materials with complete isotropy of elastic properties are obtained by laying reinforcement at an angle of 31° 43 to the axes of the Cartesian coordinate system in each of the three orthogonal planes. Other symmetries are characterized by the presence of certain extreme values ​​of physical properties.

Figure 17.15 - Diagram of the diagonal arrangement of the structure in one plane ( A) and in space ( b) for composite materials formed by the system n threads; eleven-directional (11d) reinforcement pattern ( V), diagonals between diametrical vertices along two faces and along edges.

For the rational use of reinforced composite materials, it is necessary to know their maximum reinforcement coefficients. The work explored the possibilities of limiting filling of spatially reinforced structures with fibers of round cross-section. Basically, they studied the dense packing of fibers - when touching their cylindrical surfaces - in one plane, perpendicular to which fibers were introduced, “fastening” the layers. Table 17.14 shows the theoretical maximum permissible values ​​of reinforcement coefficients for some types of structures in the case where multidirectional in-plane reinforcement was created by straight fibers. Parameter  (%) indicates the proportion of straight fibers orthogonal to the laying plane in the total volume of the reinforcement.

Table 17.14 - Limit reinforcement coefficients for some types of structures.

№ p/p	Reinforcement scheme	Number reinforcement directions	Laying fibers	Proportion of fibers orthogonal to the packing plane, %	 etc
			Hexagonal
			Rectangular
			Layered (arbitrary)
			Rectangular in three planes
			Hexagonal transversally isotropic

As can be seen from the data in Table 17.14, the deviation of the fiber laying directions from the unidirectional and flat pattern significantly reduces the volumetric reinforcement coefficient of the material. With three mutually orthogonal directions of fiber laying, the maximum reinforcement coefficient  pr. is reduced by 25% compared to the coefficient for a continuous structure. With four directions of reinforcement, three of which create isotropy of properties in the plane (Table 17.14, clause 5),  etc the reinforcement coefficient is reduced compared to the reinforcement coefficient according to the hexagonal unidirectional pattern (Table 17.14, paragraph 1) by 38%. In scheme 5, due to the oblique laying of fibers in a plane, when they touch fibers in a direction orthogonal to the plane, there are more vacancies to fill with the matrix than in the case of three orthogonal directions of reinforcement (Table 17.14, paragraph 4).

It should be noted that idealized schemes for the maximum filling of a composite material with fibers should be considered only for comparison. In real cases, due to technological or other conditions, the distances between adjacent fibers change, and it is necessary to introduce corrections to  etc coefficients reflecting the degree of fiber dispersion when idealizing the geometry of the structure.

The actual volume of fibers in the frame is always significantly lower than the calculated one. This is due to the fact that the threads do not have the correct cross-sectional shape adopted in the calculation, and the elementary fibers are not monolithic.

Methods for making reinforcement frames of carbon-carbon composite materials are varied, including dry thread weaving, fabric stitching, assembling rigid rods made from pultruded carbon threads, thread winding, weaving, and a combination of these methods. The most widely used method is weaving (weaving) dry threads. It is acceptable for the manufacture of both the simplest of multidirectional frames, in which the fibers are located along the axes of a rectangular coordinate system (CR), and the most complex multidirectional ones - 11 D (see Figure 17.15, V). In this case, small-diameter threads are used with their dense laying (Figure 17.16), which ensures small voids and high frame density.

The dry thread weaving method is also applicable for creating cylindrical frames. Woven scaffolds of this type are shown in Figure 17.17. Ensuring a constant density of reinforcement for cylindrical frames with increasing divergence of radial threads as they approach the outer diameter is achieved by increasing the diameter of the axial bundles of threads or introducing radial elements of different lengths into the main reinforcement system. The production of such frames is carried out on weaving machines. It is possible to create more complex structures.

Figure 17.16 - Typical layout of small-diameter fibers in orthogonally reinforced material in order to obtain a high frame density.

Figure 17.17 - Arrangement of threads in a three-directional cylindrical

weave .

The development of methods for producing orthogonally reinforced frames made it possible to create a modified structure called Mod 3. The modification was as follows: in the plane xy Instead of straight threads, carbon fabric is used, the fibers are in the direction of the axis z remain straight and pass through the layers of fabric between the fibers in a plane xy. When sewing fabric in the direction of the axis X Both dry threads and carbon rods are used, obtained by impregnation of the threads either with an organic binder followed by carbonization, or with pyrolytic carbon from the gas phase. The type and distribution of fibers in scaffolds of this structure can vary in all directions.

Multidirectional frames are also produced from carbon rods alone. The disadvantage of such scaffolds is the lack of integrity before the introduction of the matrix connecting the rods; the advantage lies in the high degree of filling of the volume of material with reinforcement.