Carbon-Carbon Composites: Properties, Applications and Limitations
Introduction
Carbon fibre reinforced carbon (CFRC), also known as carbon-carbon (C/C) or reinforced carbon-carbon (RCC), is a composite material with a long history of use in high-performance applications. It consists of carbon fiber reinforcement embedded in a matrix of graphite, which gives it excellent structural properties at high temperatures, low coefficients of thermal expansion, and good resistance to thermal shock. In this article, we will discuss the properties, applications, and limitations of carbon-carbon composites.
Development and Properties
Carbon-carbon composites were initially developed for reentry vehicles of intercontinental ballistic missiles due to their ability to withstand extreme temperatures and thermal shock. The material’s most well-known application is in the nose cone and wing leading edges of the Space Shuttle orbiter. Its unique combination of properties arises from the synergy between the carbon fibers and the graphite matrix.
Carbon fibers contribute to the material’s tensile strength, stiffness, and resistance to cracking. On the other hand, the graphite matrix provides excellent thermal conductivity, contributing to the composite’s ability to dissipate heat rapidly. This heat dissipation is critical in high-temperature applications where thermal gradients can lead to material failure. Furthermore, the graphite matrix provides a high degree of dimensional stability, with a low coefficient of thermal expansion. This ensures that the material maintains its shape and dimensions under varying temperatures.
Applications
- Space Exploration: The most famous application of carbon-carbon composites is in the Space Shuttle program. The material’s resistance to extreme temperatures and thermal shock made it ideal for the orbiter’s nose cone and wing leading edges, which experienced temperatures exceeding 3000°F (1650°C) during atmospheric reentry.
- Formula One Racing: Since the late 1970s, carbon-carbon brake discs and brake pads have been the standard component of brake systems in Formula One racing cars. The first year carbon brakes were seen on a Formula One car was in 1976. Carbon-carbon composites offer several advantages in this application, including high thermal conductivity for efficient heat dissipation, low weight for improved vehicle performance, and excellent wear resistance, which ensures consistent braking performance over the course of a race.
- Aerospace Industry: Carbon-carbon composites are used in aircraft brake systems, engine components, and other high-temperature applications where weight reduction and thermal management are critical.
- Nuclear Industry: Carbon-carbon composites have found applications in nuclear reactors due to their excellent thermal and dimensional stability, as well as their resistance to radiation damage.
Limitations and Challenges
Despite their impressive properties and numerous applications, carbon-carbon composites have some limitations. One notable drawback is their lack of impact resistance. The Space Shuttle Columbia disaster in 2003 highlighted this vulnerability when a piece of polyurethane foam insulation broke off from the Space Shuttle External Tank and damaged one of the orbiter’s RCC panels. The damaged panel led to the catastrophic failure of the spacecraft during atmospheric re-entry.
Another challenge is the high cost of carbon-carbon composites, which arises from the complexity of their manufacturing process. The production of carbon-carbon composites involves multiple stages, including the preparation of carbon fibers, infiltration of the fibers with a carbon precursor, and high-temperature heat treatments. This complexity makes carbon-carbon composites more expensive than many other materials, limiting their widespread adoption.
Conclusion
Carbon-carbon composites are a unique class of materials with exceptional properties that make them well-suited for high-temperature structural applications. Their use in the Space Shuttle program, Formula One racing, and other industries has demonstrated their potential for withstanding extreme conditions. However, their limitations, such as impact resistance and high cost, must be considered when evaluating their suitability for specific applications
