carbon fibres type IM

https://doi.org/10.1351/goldbook.C00835
Carbon fibres type IM (intermediate modulus) are related to @[email protected] because of the comparable values of tensile strength, but are characterized by greater stiffness (@[email protected] up to approximately 35% of the theoretical \(C_{11}\) value).
Note:
The tensile modulus (@[email protected]) varies between ca. \(275\) and \(350\ \text{GPa}\), but the disposition of the boundaries is somewhat arbitrary. The relatively high ratio of tensile strength to tensile modulus, typically above \(1 \times 10^{-2}\), in carbon fibres type IM, in spite of an increase of @[email protected], requires a further increase of strength, which is achievable by a significant reduction of the monofilament diameter down to about \(5\ \unicode[Times]{x3BC}\text{m}\). Such small filament diameters are typical of carbon fibres type IM.
Source:
PAC, 1995, 67, 473. (Recommended terminology for the description of carbon as a solid (IUPAC Recommendations 1995)) on page 482 [Terms] [Paper]