good afternoon, dear listeners. topic of the lecture Carbon fibers for PCM reinforcement Carbon fibers are one of the main types of reinforcing components used to create high modulus, high strength composite materials Carbon fibers are widely used due to their high mechanical properties The possibilities of using carbon fibers are determined by the structure of graphite, of which they are composed and the theoretical values of its characteristics The theoretical ultimate strength and elastic tension modulus along atomic planes are, respectively 100 and 1000 GPa (for comparison, the real elastic modulus of steel is 200 MPa) Depending on the degree of realization of the potential properties it is common practice to subdivide fibers into graphite and carbon Fibers with a high degree of orientation of atomic planes re called graphite fibers, which manifests itself in high values of the elastic modulus (more than 345 GPa), carbon fibers are fibers with lower characteristics (the elastic modulus does not exceed 345 GPa) The creation of carbon fiber involves both chemical and mechanical processes The raw materials, or precursors, are drawn into long strands and then heated to high temperatures in an anaerobic oxygen-free) environment After the carbonation process is complete, the remaining fiber consists of long, closely interconnected chains of carbon atoms In the process of obtaining PAN-based carbon fibers the following stages are involved forming the original PAN fiber preliminary drawing stabilization at a temperature of about 220 � C in air under tension carbonization at 1500 � C in an inert gas atmosphere graphitization at 3000 � C in an inert gas atmosphere surface treatment Polyacrylonitrile is a linear polymer The presence of nitrile groups provides a relatively strong intermolecular interaction, which manifests itself in a sufficiently high vitrification temperature of PAN (about 120 � C) and makes it difficult to spin fibers at lower temperatures PAN fibers are formed mainly by dissolving the polymer and passing the solution through the spinnerets into a special bath where the solution is formed into fibers (coagulation) Before carbonizing the fibers, they must be chemically altered to convert their linear atomic bond into a more heat-resistant ladder bond This is achieved by heating the fibers in air to about 200-300 � C for 30-120 minutes The next step is carbonization of the PAN fiber Once the fibers are stabilized, they are heated to a temperature of about 1800 � C for a few minutes in an oven filled with a gas mixture that does not contain oxygen Graphitization is carried out at temperatures above 1800 � C and is intended to increase the carbon content in the fiber and increase its elastic properties An increase in elasticity is achieved by the ordering of the crystal structure and the creation of a preferential orientation of the crystals As a cheap raw material, pitches can reduce the cost of carbon fibers and expand the use of these materials Thus, concurrently with the development of PAN-based carbon fibers, efforts have also been made to develop resin-based carbon fibers Otani (1965) developed the first carbon fiber based on isotropic pitch Mechanical properties were not very attractive, and the fibers were called general purpose carbon fibers Cellulose fiber as a precursor was first used by Thomas Edison in the 1880s as the base for his revolutionary filament incandescence Much later, in 1959, the National Carbon Company introduced viscose fiber carbon cloth in 1959, and two years later carbon fiber became available In 1965, the Thornel series of carbon fibers were produced in which properties were improved by post-carbonization treatment involving stretching at 2500 � C This fiber had a tensile strength of 1.25 GPa and the Young's modulus of 170 GPa Cellulose is a promising precursor for the production of carbon fiber cellulose fibers have a well-ordered crystalline structure and cellulose undergoes thermal decomposition without melting In addition, as a result of pyrolysis, a strong fibrous carbonaceous material is formed, and cellulose precursors have high thermal conductivity high purity, mechanical flexibility and low cost PAN carbon fibers are notable for their high physical and mechanical properties and high cost Pitch-based carbon fibers are much cheaper, their properties are comparable to PAN-based low-modulus fibers and have potential for improving their characteristics, which makes them very promising for the use as reinforcing elements Viscose-based CFs have the lowest characteristics, but at the same time they can be the cheapest due to the cheapness of raw materials Carbon fibers can be produced in various forms chopped (cut, short) yarns, continuous yarns woven and nonwoven materials The most common type of products are tows yarns, rovings, nonwoven canvases All types of textile products are manufactured using conventional technologies similar to those for other types of fibers The type of textile product is determined by the method of using carbon fibers in the composite material, just like the method of obtaining the composite itself The main methods for producing composites are also common laying out, injection molding, pultrusion Carbon plastics are widely used in aviation rocketry, and in the manufacture of sports equipment bicycles, cars, tennis rackets, fishing rods, etc. In addition, carbon fibers and carbon fiber reinforced plastics have a very low, almost zero coefficient of linear expansion which makes them indispensable in some special applications for example, in space telescopes or other similar elements of space technology