Читать книгу Carbon Nanofibers - Группа авторов - Страница 23

It is difficult to give the properties of carbon fibers by quantity because that depends on how the fiber was made and what treatments were done to the fiber. Here we give properties qualitatively only. Specific strength of carbon fiber (which is the ratio of strength to weight) is very high. Strength of material is the ratio of the force per unit area applied to fiber at which it breaks to its density. Carbon fiber is very rigid, i.e., its Young’s modulus is high. In other words, it needs high force to deflect it. The fiber is chemically stable and resistant to corrosion. Carbon fiber is electrically conductive and is resistant to fatigue, especially its composites. Carbon fiber has good tensile strength, which means it can stand maximum stress while it is stretched or pulled. Carbon fibers are normally fire resistant/nonflammable in the absence of oxygen. They are a good thermal conductor. Carbon fibers have a unique property of low coefficient of thermal expansion. They are nonpoisonous, biologically inert and X-ray permeable. These properties are especially good for any medical applications.

Some general properties of PAN-based fiber are given below, but these values may be different if PAN-based fibers are prepared under some specific condition. Hence, these data can be taken as approximate values.

 Density: 1750–1870 kg/m3

 Tensile strength: 0.9–6.37 kN/mm2

 Young’s modulus: 40–588 kN/mm2

 Elongation: 0.7%–2.2%

 Filament diameter: 4.4–7.2 μm

 Tensile strength of carbon fiber: 4127 MPa

 Carbon fiber reinforced epoxy (thermal conductivity): 24 W/(m.K)