Carbon Fiber

Carbon fiber, frequently used in industries such as aerospace, automotive, construction, sports, and many others, is a leading engineering material known for its high strength, light weight, chemical resistance, and aesthetic qualities. It is a lightweight yet incredibly strong material made from carbon atoms arranged in a regular pattern, typically produced as fine fibers on a microscopic scale.

Carbon fiber roll

Carbon Fiber Key Properties

• Lightweight: Carbon fiber can be up to five times lighter than steel.
• High Strength: Its tensile strength is extremely high (typically between 3.5-6 GPa).
• Hardness: The elastic modulus usually ranges from 200-700 GPa.
• Chemical Resistance: It is highly resistant to most chemicals and corrosion.
• Heat Resistance: It can withstand high temperatures and shows low thermal expansion.
• Electrical Conductivity: It is an electrically conductive material.

Carbon Fiber Production

In carbon fiber production, raw materials such as polyacrylonitrile (PAN) or petroleum-based pitch are typically used. The PAN precursor, obtained by passing the material through a coagulation bath, undergoes a series of thermal processes to produce carbon fiber.

PAN Precursor Production

PAN fibers are extended up to five to ten times their original length to improve their mechanical properties, then go through three heating processes. The first process, called stabilization, involves passing the fibers through an oven at temperatures between 200-300°C to stabilize their size for subsequent high-temperature processes. The second process, called carbonization, involves pyrolysis in a nitrogen or argon atmosphere at temperatures between 1000 and 1500°C. Pyrolysis is defined as the breakdown of complex organic material into simpler forms via heat. In the final process, called graphitization, heat treatment is applied up to approximately 2500°C. During the last two heating processes, the fibers may also undergo a tensioning process to enhance their thermal resistance. At the end of this three-step thermal process, the fibers are subjected to a surface thermal treatment to improve their bonding strength in composite structures and increase ILSS (interlaminar shear strength). They are then wound into a spool.

Applications of Carbon Fiber

Carbon fibers are produced in bundles made up of filaments with thicknesses ranging from 5 to 10 microns, and can be found in different grades such as 3K, 6K, 12K, and 24K. The application areas vary according to the fiber density:

• 3K: Ideal for lighter and finer tasks; known for its flexibility and classic aesthetic.
• 6K: A balanced choice in terms of both strength and lightness; suitable for medium-scale structures.
• 12K and 24K: Thicker and heavier; preferred for large-scale industrial and structural projects.

Carbon fibers are generally categorized into four different classes based on their required strength in the application:

• Ultra High Modulus (UHM) (>500 GPa)
• High Modulus (HM) (>300 GPa)
• Intermediate Modulus (IM) (>200 GPa)
• High Temperature (HT) (>4 GPa)