carbon fibres type HM
Carbon fibres type HM (high modulus) are @C00831@ with a value of @Y06733@ (tensile modulus) larger than \(300\ \text{GPa}\) (nearly 30% of the \(C_{11}\) elastic constant of a @G02684@ single crystal).
The level of the tensile modulus of carbon fibres is controlled by the degree of preferred orientation of the layer planes in the direction parallel to the fibre axis. \(C_{11}\), the elastic constant of @G02684@ single crystals in the direction of the layer planes, is \(1060\ \pm 20\ \text{GPa}\). In general, the ratio of tensile strength to tensile modulus is smaller than \(1 \times 10^{-2}\) for carbon fibres type HM (but the tensile strength is influenced by flaws in the fibres and may be improved in the future). Carbon fibres type UHM (ultra-high modulus) have moduli of elasticity in excess of \(600\ \text{GPa}\), surpassing 50% of the theoretical \(C_{11}\) number. Such high values of @Y06733@ can be achieved most readily in @M03851@ (@M04038@).
PAC, 1995, 67, 473. (Recommended terminology for the description of carbon as a solid (IUPAC Recommendations 1995)) on page 481 [Terms] [Paper]