How is carbon fiber manufactured?
Carbon fiber is made from polyacrylonitrile (PAN) fibers. These PAN fibers are obtained through polymerization, spinning, and stretching of polymers. The obtained polymer chains are arranged along the filament axis direction. This is crucial for obtaining the characteristics of carbon fiber.
Then, PAN fibers are converted into carbon fibers through carbonization process. The first step is called oxidation, which makes polyacrylonitrile fibers non flammable. Oxidation occurs between 200 and 300 ° C. In this step, tension is applied to the fiber filaments to ensure that the polymer chains remain aligned correctly.
In the next step, called carbonization, heat is applied to the fibers to remove non carbon atoms and retain only carbon atoms. At a temperature of approximately 1500 ° C, oxidized polyacrylonitrile fibers react in an inert atmosphere to form characteristic graphite planes of carbon fibers.
Carbon fiber can undergo a second heat treatment at temperatures above 2 ° C. Under the action of heat, the crystal structure of carbon fiber transforms into high modulus carbon fiber.
Then, the carbon fiber undergoes surface treatment: chemical electrolysis. It allows grafting oxygen groups on the surface of the filament. These oxygen groups prepare the fibers for the final part of the carbonization process: the application of sizing treatment. Glue application is used to promote the adhesion between fibers and polymer matrix in composite materials. This optimizes the subsequent processing of carbon fiber.
Characteristics of carbon fiber
Lightweight attributes
Carbon fiber is very light because the atomic mass of carbon atoms is very low. In addition, the chemical structure composed of graphite planes arranged in crystals results in a larger spacing between carbon atoms.
Mechanical performance
Carbon fiber is very strong and rigid (high modulus). Covalent bonds bind carbon atoms in the graphite plane. These chemical bonds are very stable: due to the shared electrons between carbon atoms, a large amount of energy is required to break covalent bonds.
The structure of carbon fiber also plays an important role in the strength and resistance of materials.
Therefore, carbon composite materials have unparalleled tensile strength, modulus, and fatigue resistance.
Thermal performance
Carbon fiber is heat-resistant. When used at high operating temperatures, carbon fiber will not degrade or expand.
In order to fully utilize its thermal properties, carbon fibers are sometimes combined with ceramic matrix to form ceramic matrix composites (CMC). Therefore, carbon can be considered as a ceramic material. Therefore, CMCs can still maintain their carbon characteristics at temperatures above 2 ° C.
Conductivity and resistance
Carbon fiber has conductivity. Under electric current, carbon fiber generates Joule heat. Due to its conductivity and excellent heat resistance, it provides an excellent heating solution. Carbon composite materials can also be used to protect electronic devices from radio or electromagnetic interference. Therefore, carbon composite materials act as Faraday cages.
X-ray permeability
Carbon fiber is composed of lightweight elements: 95% carbon atoms and 5% nitrogen. It absorbs very few X-rays and is very suitable for medical imaging.
Non flammable
Carbon fiber has an extremely ordered structure that can induce many strong bonds between carbon atoms. Therefore, the oxidation reaction generated in a fire cannot be self-sufficient, making this material non flammable.
Application of carbon fiber
Carbon fiber is lightweight, durable, and long-lasting, making it a cutting-edge material. It is most notably used to enhance composite materials. Mainly used in:
Aerospace industry;
Sports and leisure industry (golf clubs, fishing rods, bicycle frames);
Automotive industry;
Marine industry;
civil engineering;
The energy industry.
Carbon fiber is commonly used to reduce the weight of vehicles, airplanes, and other forms of public transportation. Aircraft made of carbon composite materials are 20% lighter than those made of traditional materials. Reducing weight by 20% throughout the entire lifecycle of an aircraft can reduce carbon dioxide emissions by 2 tons.
Automotive Industry: Hydrogen Energy Solutions
The battery life of hydrogen powered cars is now longer than that of battery powered cars (>500 kilometers). Due to the storage of compressed hydrogen gas in carbon fiber pressure tanks, this performance can be achieved. Due to its unique performance, carbon fiber is the only material that can provide the necessary strength, lightweight, and long-term performance for these fuel tanks.
Carbon paper is also a solution for producing key components of proton exchange membrane fuel cells: gas diffusion membranes.
Carbon Fiber Manufacturing
Carbon fiber is made from polyacrylonitrile (PAN) fibers. These PAN fibers are obtained through the polymerization, spinning, and stretching of the polymer. The resulting polymer chains are aligned along the filament axis, which is crucial for achieving the properties of carbon fiber.
Then, the PAN fibers are transformed into carbon fibers through a process called carbonization. The first step is oxidation, which makes the polyacrylonitrile fibers non-flammable. Oxidation occurs between 200 to 300°C. During this step, tension is applied to the filaments to ensure that the polymer chains remain properly aligned.
In the next step, called carbonization, heat is applied to the fibers to remove non-carbon atoms and retain only the carbon atoms. At approximately 1,500°C, the oxidized polyacrylonitrile fibers react in an inert atmosphere to form the characteristic graphite planes of carbon fibers.
Carbon fibers can undergo a second heat treatment at temperatures above 2,000°C. Under the influence of heat, the crystalline structure of the carbon fibers transforms into high-modulus carbon fibers.
Then, carbon fibers undergo surface treatment: chemical electrolytic treatment. This allows the grafting of oxygen groups onto the surface of the filaments. These oxygen groups prepare the fibers for the final part of the carbonization process: the application of sizing. Sizing is used to promote adhesion between the fibers and the polymer matrix of composite materials, optimizing the subsequent processing of carbon fibers.
Characteristics of Carbon Fiber
Lightweight Properties
Carbon fiber is very light due to the low atomic mass of carbon atoms. Additionally, the chemical structure composed of graphite planes arranged in crystals results in larger spacing between carbon atoms.
Mechanical Performance
Carbon fiber is extremely strong and rigid (high modulus). Covalent bonds hold the carbon atoms in the graphite planes together. These chemical bonds are very stable: since carbon atoms share electrons, a significant amount of energy is required to break the covalent bonds.
The structure of the carbon filaments also plays a crucial role in the material's strength and resistance. Consequently, carbon composites possess unparalleled tensile strength, modulus, and fatigue resistance.
Thermal Properties
Carbon fiber is heat-resistant. It does not degrade or expand when used at high operating temperatures. To fully utilize its thermal properties, carbon fibers are sometimes combined with ceramic matrices to form ceramic matrix composites (CMC). Therefore, carbon can be considered a ceramic material. Consequently, CMCs retain carbon properties even at temperatures above 2,000°C.
Electrical Conductivity and Resistance
Carbon fiber is electrically conductive. Under electrical current, carbon fiber generates Joule heat. Due to its conductivity and excellent heat resistance, it offers outstanding heating solutions. Carbon composites can also be used to protect electronic devices from radio or electromagnetic interference, thus acting as a Faraday cage.
X-Ray Penetrability
Carbon fiber is composed of lightweight elements: 95% carbon atoms and 5% nitrogen. It absorbs very few X-rays, making it ideal for medical imaging applications.
Non-Flammability
Carbon fiber has an extremely ordered structure that induces many strong bonds between carbon atoms. As a result, the oxidation reactions produced in a fire cannot sustain themselves, giving this material its non-flammable properties.
Applications of Carbon Fiber
Carbon fiber is lightweight, durable, and strong, making it a cutting-edge material. It is most notably used to reinforce composite materials. Major applications include:
- Aerospace industry
- Sports and leisure industry (golf clubs, fishing rods, bicycle frames)
- Automotive industry
- Marine industry
- Civil engineering
- Energy industry
Carbon fiber is commonly used to reduce the weight of vehicles, aircraft, and other forms of public transportation. An aircraft with a fuselage made of carbon composites is 20% lighter than one made of traditional materials. Over the aircraft's lifetime, a 20% weight reduction can decrease CO2 emissions by 2 tons.
Automotive Industry: Hydrogen Solutions
Hydrogen-powered cars now have a longer battery life than electric cars (over 500 km). This performance is possible due to the storage of compressed hydrogen in carbon fiber pressure tanks. Due to its unique properties, carbon fiber is the only material that can provide the necessary strength, lightness, and long-term performance for these tanks.
Carbon paper is also a solution for producing key components of proton exchange membrane fuel cells: gas diffusion layers.