Term: carbon fibres type IM https://doi.org/10.1351/goldbook.C00835 Definition: Carbon fibres type IM (intermediate modulus) are related to carbon fibres type HT because of the comparable values of tensile strength, but are characterized by greater stiffness (Young's modulus up to approximately 35% of the theoretical C11 value). Note: The tensile modulus (@M03966@) varies between ca. 275 and 350 GPa, but the disposition of the boundaries is somewhat arbitrary. The relatively high ratio of tensile strength to tensile modulus, typically above 1 x 10E-2, in carbon fibres type IM, in spite of an increase of @M03966@, requires a further increase of strength, which is achievable by a significant reduction of the monofilament diameter down to about 5 µm. Such small filament diameters are typical of carbon fibres type IM. Related Terms: 1) young's modulus (http://doi.org/10.1351/goldbook.M03966). 2) carbon fibres type ht (http://doi.org/10.1351/goldbook.C00834). Source: PAC, 1995, 67, 473. 'Recommended terminology for the description of carbon as a solid (IUPAC Recommendations 1995)' on page 482 (https://doi.org/10.1351/pac199567030473) Citation: 'carbon fibres type IM' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. https://doi.org/10.1351/goldbook.C00835 License: 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. Disclaimer: 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.