00833 IUPAC Gold Book - carbon fibres type HM 10.1351/goldbook.C00833 C00833 current initialisms: HM, UHM 1 Carbon fibres type HM (high modulus) are carbon fibres with a value of Young's modulus (tensile modulus) larger than \(300\ \rm{GPa}\) (nearly $\pu{30\%}$ of the \(C_{11}\) elastic constant of a graphite 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 graphite single crystals in the direction of the layer planes, is \(1060\ \pm 20\ \rm{GPa}\). 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 \(600\ \rm{GPa}\), surpassing 50% of the theoretical \(C_{11}\) number. Such high values of Young's modulus can be achieved most readily in mesophase pitch-based carbon fibres (MPP-based carbon fibres). MPP-based carbon fibres https://goldbook.iupac.org//terms/view/M04038 Young's modulus https://goldbook.iupac.org//terms/view/Y06733 carbon fibres https://goldbook.iupac.org//terms/view/C00831 graphite https://goldbook.iupac.org//terms/view/G02684 mesophase pitch-based carbon fibres https://goldbook.iupac.org//terms/view/M03851 PAC, 1995, 67, 473. 'Recommended terminology for the description of carbon as a solid (IUPAC Recommendations 1995)' on page 481 (https://doi.org/10.1351/pac199567030473) https://goldbook.iupac.org/terms/view/C00833/html https://goldbook.iupac.org/terms/view/C00833/json https://goldbook.iupac.org/terms/view/C00833/plain Citation: 'carbon fibres type HM' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. 10.1351/goldbook.C00833 The IUPAC Gold Book is licensed under Creative Commons Attribution-ShareAlike CC BY-SA 4.0 International (https://creativecommons.org/licenses/by-sa/4.0/) for individual terms. If you are interested in licensing the Gold Book for commercial use, please contact the IUPAC Executive Director at executivedirector@iupac.org . The International Union of Pure and Applied Chemistry (IUPAC) is continuously reviewing and, where needed, updating terms in the Compendium of Chemical Terminology (the IUPAC Gold Book). Users of these terms are encouraged to include the version of a term with its use and to check regularly for updates to term definitions that you are using. 2026-04-19T04:11:14+00:00