Carbon fiber reinforced polymer (CFRP) has high strength, rigidity, low weight, and excellent fatigue resistance. Compared to aluminum and steel, the specific strength of carbon fiber is about ten times higher. Over the past fifty years, CFRP has been successfully applied in aerospace, automotive, rail transport, marine, and wind energy industries.
The Meaning of Carbon Fiber
Carbon fiber is a high-performance industrial fiber, which, after fine processing, is composed almost entirely of carbon. Under a microscope, these fibers are thin, approximately only one-eighth the diameter of a human hair. To make it suitable for various applications, 1,000 to hundreds of thousands of filaments are combined into tow and wound onto spools.
The Process of Carbon Fiber Production
Carbon fiber is a product of high-tech manufacturing processes. It begins with raw materials like polyacrylonitrile (PAN), which has excellent chemical and solvent resistance. In the first processing step, PAN is formed into fibers, which are then wound onto spools. The PAN fibers undergo heat treatment, first oxidizing at 200-300°C, then carbonizing at 1200 to 1800°C. After surface treatment and sizing, the carbon fibers are wound up and ready for use.
What Does CFRP Mean?
CFRP stands for Carbon Fiber Reinforced Polymer. It is a composite material composed of matrix material and reinforcing carbon fibers embedded within the matrix. Polymers are usually used as the matrix material. Depending on the type of carbon fiber used, the type of matrix, and the manufacturing process, the cured CFRP exhibits different properties.
How is CFRP Produced?
There are various methods for producing CFRP. Due to differences in production methods, they vary in production cost, material performance, and application range. In the manufacturing process of CFRP, carbon fibers can be continuously wound or woven into carbon fiber fabrics.
Advantages of CFRP
| Lightweight: CFRP composites with 70% carbon fiber typically have a density of 0.055 lbs/in³.
| High Strength: It is lighter and stronger per unit weight. When comparing steel with CFRP, CFRP with the same strength typically weighs one-fifth as much as steel. The same-strength aluminum may weigh 1.5 times as much as the CFRP. This is why the automotive industry is increasingly using the material.
| Properties | CFRP Cable | Steel Cable |
| Tensile Strength | 2700N/mm2 | > 1670N/mm2 |
| Modulus of Elasticity | 160,000N/mm2 | 205,000N/mm2 |
| Elongation at Rapture | 1.6% | 6.0% |
| Density | 1600kg/m3 | 7850k g/m3 |
| Poisson Ratio | 0.3 | 0.3 |
| In the table, the tensile strength of steel cable is given as 1670N/mm2 whereas that of CFRP cables | ||
| High Mechanical Performance: They have improved mechanical performance while reducing weight, making them particularly suitable for use as raw materials in various lightweight, high-strength sports equipment.
| Good Damping: Polymer has a noticeable long-chain structure. When polymers deform, their movement exhibits both viscous and elastic characteristics, giving them viscoelasticity. In CFRP materials, there are many fine cracks at the interface between the carbon fibers and the polymer. When the material vibrates due to external force, there is friction at these interface cracks. When the external force is removed, part of the kinetic energy is converted into heat due to friction, leading to energy loss, which is manifested as good damping in the material.
| High Safety Level: It is a kind of composite material with strength and impact resistance that is significantly better than traditional metal materials. In the event of overload, they do not fracture. Additionally, because of the presence of carbon fibers, the fracture of some fibers does not affect the performance of the remaining fibers, ensuring the composite material’s strength and making it less prone to brittle fracture, thereby enhancing its safety.
Disadvantages of CFRP
| Cost: Despite the impressive material properties, it is quite expensive. The cost of carbon fiber materials per pound is 5 to 25 times more than that of fiberglass. The price difference is even greater when comparing steel with CFRP.
Factors affecting the cost include market supply and demand, the type of carbon fiber (aerospace grade or commercial grade), and fiber tow size.
Applications of CFRP
| Aviation: With technological advancements, both the carbon fiber and the polymer properties have significantly improved, enhancing CFRP’s performance. This has allowed the material to be used in major aircraft structures such as fuselages, vertical stabilizers, tail fin boxes, and wings, replacing traditional lightweight metal alloys. Today, it is widely used in the A380 aircraft, accounting for over 50% of its weight.
| Automotive: Due to the advantages of carbon fiber in reducing vehicle weight and improving strength performance, it is widely used in automotive body structures, such as body panels and roof components. It is estimated that by 2030, carbon fiber consumption in the automotive field will reach 90,000 to 100,000 tons.
| Medical Field: Many types of polymer matrices can be combined with carbon fiber using various manufacturing methods to form composites with different properties. Due to its high strength, lightweight, and radiolucency, they are replacing traditional metal implants.
| Wind Energy: In wind turbine applications, carbon fiber has a higher specific modulus than glass fiber, allowing for longer blades and more aerodynamic designs. The emergence of textile-grade carbon fibers with 300-450k tow sizes, modulus ranging from 260 to 290 GPa, and tensile strengths from 1700 to 2700 MPa is well-suited for modulus-driven applications in the automotive and wind energy fields, further promoting the use of carbon fiber in wind energy.
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