carbon fibres type HM

https://doi.org/10.1351/goldbook.C00833
Carbon fibres type HM (high modulus) are @[email protected] with a value of @[email protected] (tensile modulus) larger than \(300\ \text{GPa}\) (nearly 30% of the \(C_{11}\) elastic constant of a @[email protected] single crystal).
Note:
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 @[email protected] 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 @[email protected] can be achieved most readily in @[email protected] (@[email protected]).
Source:
PAC, 1995, 67, 473. (Recommended terminology for the description of carbon as a solid (IUPAC Recommendations 1995)) on page 481 [Terms] [Paper]