Carbon Fiber Carbon fiber is a substance made of carbon atoms linked together in long chains to form thin, strong crystalline filaments. The fibers are utilized in numerous processes to produce top-notch structural materials since they are incredibly stiff, robust, and light. Properties of Carbon Fiber: 1. Strength to Weight Ratio of Carbon Fiber is High (specific strength): Strength to weight ratio, or specific strength, which is defined as the force per unit area at failure divided by the density of the material. A favourable Strength/weight ratio can be found in any material that is both strong and light. 2. Carbon fiber has a high Young Modulus, which evaluates how much a material deflects under stress and is a measure of a substance's stiffness or rigidity. More than four times as stiff as glass reinforced plastic, over twenty times stiffer than pine, and 2.5 times stiffer than aluminium alloys is carbon fiber reinforced plastic. 3. Although carbon fiber doesn't decay on its own and is chemically stable, epoxy needs to be covered from sunshine because it is photosensitive. The carbon fiber may also be embedded in reactive other matrices. 4. Both a benefit and a drawback exist for this trait. Galvanic corrosion in fittings can be facilitated by carbon fiber conductivity. Installation done carefully can lessen this issue. A buildup of carbon fiber dust in a shop may result in sparks or short circuits in electrical apparatus. 5. It's good that carbon fiber composites have strong fatigue resistance. However, when carbon fiber fails, it typically does so in a catastrophic way with little to no warning that it is about to shatter. With more stress cycles, damage in tensile fatigue is visible as a drop in stiffness (unless the for the higher temperature). 6. The tensile strength of carbon fiber is good. The maximum stress that a material can bear when being stretched or pulled before necking, or failing, is known as tensile strength or ultimate strength. The sample cross-section begins to noticeably compress, which is known as necking. If you stretch a piece of plastic bag, it will eventually start to get narrow. It's necking. Force per Unit area is the unit of measurement. Due to inherent defects, brittle materials like carbon fiber do not always fail at the same stress threshold. They break under light stresses. 7. Fire Resistance/Non-Flammable: Carbon fiber can be relatively soft and can be produced into or more frequently integrated into protective garments for firefighting, depending on the manufacturing process and the precursor material. One illustration is fiber that has been treated with nickel. Carbon fiber can be used in environments with fire and corrosive substances because it is chemically very inert. The use of a carbon fiber blanket during welding. 8. Thermal Conductivity of Carbon Fiber: Under steady-state conditions, thermal conductivity is the amount of heat that is transferred through a unit thickness in a direction normal to a unit-area surface due to a unit temperature gradient. Applications 1. Carbon fibre in Engineering: Because of its potential construction advantages and affordability, carbon fiber reinforced polymer is used in a number of structural engineering applications. Strengthening structures constructed of concrete, steel, wood, masonry, and cast iron are some of the typical applications; 2. Carbon Fiber in Flight: The higher strength to weight ratio of carbon fiber greatly outshines that of any metal, and it has been utilized in spacecraft that have traveled to the moon. Medical Applications: In the medical industry, carbon fiber has a number of benefits over other composites, given the fact that it is radiolucent transparent to X-rays and appears as black on X-ray images. Military application: Applications in the military range widely and provide strengthening and weight reduction for all military equipment, from aircraft and missiles to protective helmets. Automobile Industry: Carbon fiber is being used increasingly frequently in autos as prices decrease. Supercar bodywork are already constructed, but its more widespread application is anticipated to be found in internal parts like instrument housings and seat frames. Fabrication Process Raw Materials Carbon fibers from polyacrylonitrile (PAN): Precursor is the name given to the basic ingredient required to create carbon fiber. Polyacrylonitrile is used to make around 90% of the carbon fibers that are manufactured. The remaining 10% are made of petroleum pitch or rayon. These substances are all organic polymers, which have lengthy chains of molecules joined by carbon atoms. Different gases and liquids are employed during the manufacturing process. Some of these substances are intended to interact with the fiber to produce a certain outcome. Fabrication Process Spinning i. To create polyacrylonitrile plastic, acrylonitrile plastic powder is combined with another plastic, such as methyl acrylate or methyl methacrylate, and polymerized using a catalyst in a traditional suspension or solution polymerization method. ii. After that, the plastic is spun into fibers via a variety of techniques. Some processes involve mixing the plastic with specific chemicals and pumping the mixture through tiny jets into a chemical bath or quench chamber, where it congeals and forms into threads. iii. In other processes, the heated plastic mixture is forced into a chamber through tiny jets, where the solvents evaporate, leaving a solid fiber. After being stretched to the desired fiber diameter, the fibers are cleaned. Stabilization The fibers must undergo chemical modification before carbonization in order to change their linear atomic bonding to a more thermally stable ladder bonding. The fibers in the air are heated for 30120 minutes at a temperature of around 390-590° F (200-300° C) to achieve this. As a result, the fibers absorb oxygen molecules from the atmosphere and change the way their atomic bonds are arranged. The chemical reactions that stabilize materials are intricate and include multiple steps, some of which take place concurrently. Additionally, they produce heat on their own, which needs to be managed to prevent overheating the fibers. The stabilization procedure is carried out commercially with a range of tools and methods. The fibers are pulled through a series of heated chambers in some processes. Carbonization After the fibers have been stabilized, they are heated for a number of minutes in a furnace with a gas mixture devoid of oxygen to a temperature of roughly 1,830-5,500° F (1,000-3,000° C). The fibers can't burn in the extremely high temperatures because there isn't enough oxygen present. The locations where the fibers enter and exit the furnace are sealed to prevent oxygen from entering, and the gas pressure inside the furnace is kept higher than the air pressure outside. As the fibers heat up, they start to release various gases such water vapor, ammonia, carbon monoxide, carbon dioxide, hydrogen, nitrogen, and others in addition to a few carbon atoms. Surface treatment The fibers' surface after carbonization makes it difficult for them to adhere to the epoxies and other components used in composite composites. The surface of the fibers is slightly oxidized to improve their bonding abilities. Better chemical and mechanical bonding qualities are produced by the addition of oxygen atoms to the surface, which also etches and roughens the surface. The fibers can be exposed to various gases, such as air, carbon dioxide, or ozone, or various liquids, such as sodium hypochlorite or nitric acid, to oxidize them. By making the fibers the positive terminal in a bath of several electrically conductive materials, the fibers can also be coated electrolytically. To prevent generating minute surface flaws, the surface treatment procedure must be carefully managed. Sizing The fibers are coated after the surface treatment to shield them from abrasion during winding or weaving. This procedure is known as sizing. Products for coatings are chosen so that they work well with the adhesive that is used to create composite materials. The usual coating materials include nylon, urethane, polyester, epoxy, and others. The coated fibers are threaded onto bobbins, which are cylindrical objects. The fibers are twisted into yarns of various sizes by loading the bobbins into a spinning machine.
