Each carbon fiber is made up of thousands of smaller carbon fibers, about 5 to 8 microns in diameter, almost entirely composed of carbon. The earlier generations (such as T300, HTA and AS4) have a diameter of 16-22 microns. Newly developed carbon fibers (such as IM6 or IM600) are approximately 5 microns in diameter. At the atomic level, carbon fibers are very similar to graphite and consist of a layer of carbon atoms arranged in a hexagonal pattern (graphene sheets). The difference between the two lies in the way the layers are connected. Graphite is a crystal structure in which the interlayer bonds are loose, while carbon fibers are not crystalline structures, and interlayer connections are irregular. This prevents slippage and enhances material strength. The density of carbon fiber is generally 1750 kg/m3. The heat conductivity is high but the power transmission capacity is low. The specific heat capacity of carbon fiber is also lower than that of copper. When heated, the carbon fiber will become thicker and shorter. Although the natural color of carbon fiber is black, it can be dyed in different colors.

Field of application
The tail of the RC helicopter is made of carbon fiber reinforced polymer (English: Carbon fiber reinforced polymer). In 2009, the global demand for carbon fiber composites was approximately $10.8 billion, a decrease of 8-10% from the previous year. It is expected to reach US$13.2 billion by 2012 and increase to US$18.6 billion by 2015, with an annual growth rate of over 7%. Strong demand comes from aircraft and aerospace, wind power, and from the automotive industry. Because carbon fiber is light and hard, it is widely used.