Full definition
Carbon fiber is a high-performance material primarily composed of over 92% carbon atoms. It is produced through a controlled process known as pyrolysis, where precursor fibers such as polyacrylonitrile (PAN) or pitch are subjected to high temperatures in an inert atmosphere. The resulting carbon filaments have a diameter ranging from 5 to 10 μm and are typically bundled into tows containing between 1,000 to 48,000 filaments. These tows are then combined with a polymer matrix, commonly epoxy resin, to create carbon fiber reinforced polymer (CFRP). This composite material exhibits remarkable mechanical properties, including tensile strengths of 3,500 to 7,000 MPa, making it 5 to 10 times stronger than steel. With an elastic modulus of 230 to 600 GPa and a density of 1.75 to 1.95 g/cm³, CFRP provides the highest specific strength and stiffness among engineering materials, making it suitable for a variety of applications.
The types of carbon fiber are classified based on their modulus, including standard modulus (e.g., T300, T700), intermediate modulus (e.g., T800), and high modulus (e.g., M40, M55). Manufacturing processes for carbon fiber and CFRP involve several methods, including prepreg layup combined with autoclave curing, filament winding, pultrusion, and resin transfer molding. Each method is selected based on the desired properties of the final product and the specific application requirements.
Carbon fiber is widely utilized in industries such as aerospace, where the Boeing 787 Dreamliner incorporates approximately 50% CFRP in its structure for weight reduction and increased fuel efficiency. Other applications include high-performance automotive components like Formula 1 chassis, wind turbine blades, sporting goods such as bicycles and tennis rackets, medical devices such as prosthetics, and industrial rollers. According to ASTM D3039, tensile testing is essential for determining the mechanical properties of CFRP. However, it is important to note that carbon fiber has limitations, including its brittle failure mode, high production costs ranging from $15 to $150 per kilogram, and sensitivity to UV light which necessitates protective coatings to extend its lifespan.