Structural Characteristics of Polyacrylonitrile-Based Carbon Fibers
Polyacrylonitrile (PAN)-based carbon fibers are a type of inorganic fiber material with a carbon content of over 90%, appearing black in color. The diameter of the fibers varies depending on their specific performance requirements. PAN-based carbon fibers exhibit a hybrid structure comprising both random layered graphite structures and graphite-like structures. The size and orientation of the graphite structures within the carbon fibers determine their modulus, which is also one of the factors influencing their strength.
The bulk density of carbon fiber is 1.7–2.0 g/cm³, making it easy to produce lightweight composite materials. Its tensile strength typically ranges from 2.0 to 7.0 GPa, with a tensile modulus of 200–680 GPa, exhibiting extremely high strength and modulus. The elongation at break is 1.5%–2.2%, and it exhibits anisotropy, is weavable, offers high design flexibility, and has excellent processing performance. It has a low thermal expansion coefficient, ensuring good dimensional stability of the product, and exhibits excellent vibration damping characteristics. It demonstrates strong adaptability to sudden changes in environmental conditions, has good thermal and electrical conductivity, and does not exhibit heat accumulation or overheating phenomena. It has good biocompatibility, strong physiological adaptability, excellent X-ray penetrability, outstanding mechanical properties, and superior comprehensive characteristics. Carbon fiber has become the preferred reinforcing material for advanced composite materials and an ideal filler for conjugated energy composites
Classification of Polyacrylonitrile-Based Carbon Fibers
Carbon fibers exhibit typical dual-use material characteristics: in aerospace, defense, and other military industries, they are indispensable core strategic materials; in industrial applications, they serve as foundational materials for the upgrading of high-end equipment manufacturing, widely used in shipbuilding, infrastructure construction, transportation, oil extraction, pipeline transportation, large-scale wind power, sports and leisure, and other sectors. With the development of new energy projects, such as wind power, and the application of new energy in transportation, the use of carbon fiber and composite materials reinforced with carbon fiber will significantly increase.
Carbon fiber is classified based on different raw materials, including PAN-based carbon fiber, rayon-based carbon fiber, and pitch-based carbon fiber. Among these, PAN-based carbon fiber has abundant raw material sources and superior tensile strength compared to the others, making it the most widely applied type. It is used in fields such as aerospace, sports and leisure, wind turbine blades, automotive industry, and building reinforcement, accounting for over 90% of the market share.
Based on tow specifications, carbon fiber is generally categorized into two types: large-tow and small-tow. The name is typically derived from the ratio of the number of individual filaments in the carbon fiber to 1,000, with 1K indicating that there are 1,000 filaments in a single tow. Large-tow carbon fiber generally refers to carbon fiber with a tow count of 48K or higher. Large-tow carbon fiber includes products such as 48K, 50K, 60K, 75K, 80K, 120K, 240K, and 480K, with primary applications in wind power, energy, civil engineering, and transportation. Small-tow carbon fiber generally includes products such as 1K, 3K, 6K, 12K, and 24K, with primary applications in special equipment, sports goods, and fishing gear.
Carbon fiber is typically classified based on its tensile strength and tensile modulus: High-strength carbon fiber generally refers to products with a tensile modulus of 220–240 GPa, with tensile strength ranging from 2.0 to 5.0 GPa; High-strength, medium-modulus carbon fiber generally refers to products with a tensile modulus of 260–310 GPa and tensile strength of 5.0–7.0 GPa; High-modulus carbon fiber refers to carbon fiber products with a tensile modulus above 350 GPa and tensile strength slightly lower than that of traditional high-strength carbon fiber; high-strength high-modulus carbon fiber refers to carbon fiber products with a tensile modulus above 350 GPa and tensile strength above 2.5 GPa.