1. Introduction to Carbon Fiber Composites
Carbon fiber composites (Carbon Fiber Reinforced Polymer/Plastic, CFRP) are structural materials made by combining carbon fibers with matrices such as resin, ceramics, and metals. As one of the most advanced composite materials globally, CFRP offers a range of excellent properties, including high strength, low weight, high-temperature resistance, and corrosion resistance. These attributes have made it widely used in aerospace, shipbuilding, automotive manufacturing, and defense industries.
2. Classification of Carbon Fiber Composites
2.1 Carbon Fiber Ceramic Matrix Composites
Ceramic materials are known for their excellent corrosion resistance, wear resistance, high-temperature resistance, and chemical stability, making them widely used in industrial and consumer products. However, ceramics are highly sensitive to microscopic defects such as cracks, pores, and inclusions. The introduction of carbon fibers can effectively improve the toughness of ceramics, prevent brittle fracture, and slow the propagation of cracks within the matrix. Currently, carbon fiber-reinforced silicon carbide is one of the most mature carbon fiber-reinforced ceramic materials, known for its outstanding high-temperature mechanical properties. This material is widely used in aerospace engines and reusable space vehicles due to its ability to operate at high temperatures without the need for additional insulation.
2.2 Carbon/Carbon Composites
Carbon/Carbon (C/C) composites, also known as carbon fiber-reinforced carbon matrix composites, are high-performance composite materials made from carbon fibers or fabrics combined with carbon-based matrices. These materials are composed primarily of different forms of carbon, including fiber carbon, resin carbon, and deposited carbon. C/C composites, made entirely from carbon, exhibit a range of superior properties, such as high strength, rigidity, dimensional stability, oxidation resistance, and wear resistance. They also possess high fracture toughness and pseudo-plasticity. In high-temperature environments, C/C composites retain their strength, are non-melting and non-combustible, and only undergo uniform ablation, which surpasses the performance of any metal material. Therefore, they are widely used in advanced fields such as missile warheads, solid rocket motor nozzles, and aircraft brake discs.
2.3 Carbon Fiber Metal Matrix Composites
Carbon fiber-reinforced metal matrix composites are materials that use carbon fibers as reinforcement and metals as the matrix. Compared to traditional metals, they offer higher specific strength and modulus, while also providing greater toughness and impact resistance than ceramics. Commonly used metal matrices include aluminum, magnesium, nickel, titanium, and their alloys. Among these, carbon fiber-reinforced aluminum and magnesium composites are the most technically mature. One of the main technical challenges in producing these composites is the surface coating of carbon fibers, which prevents damage during the composite manufacturing process and ensures optimal performance. Techniques such as chemical vapor deposition and liquid sodium treatment are commonly used for surface modification, but their complexity and high cost have limited the widespread adoption of these materials.
2.4 Carbon Fiber Resin Matrix Composites
Carbon fiber-reinforced resin matrix composites (CFRP) are among the most advanced composite materials available today. Known for their lightweight, high strength, heat resistance, corrosion resistance, and excellent thermodynamic properties, CFRP is widely used as structural materials and high-temperature ablative materials, surpassing other fiber-reinforced composites in performance. The resin matrix used in CFRP can be categorized into two types: thermosetting resins and thermoplastic resins. Thermosetting resins, such as epoxy, bismaleimide, polyimide, and phenolic resins, undergo cross-linking and polymerization reactions when cured under heat or with curing agents, resulting in a stable, insoluble structure. In contrast, thermoplastic resins are composed of linear polymers that melt and dissolve under specific conditions, undergoing only physical changes. Common thermoplastics include polyethylene, nylon, polytetrafluoroethylene (PTFE), and polyetheretherketone (PEEK).
In CFRP, carbon fibers serve as the primary reinforcing material, while the resin matrix holds the composite together, transferring loads to the carbon fibers. Thus, the choice of matrix material significantly impacts the technical performance, processing techniques, and cost of the final product. The method of fiber reinforcement also plays a critical role in determining the composite's performance. CFRP is commonly used in everyday items, sports equipment, and automotive components, making it the most widely utilized type of carbon fiber composite in daily life.
