carbon fibres type IM

https://doi.org/10.1351/goldbook.C00835
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 (
Young's modulus
) 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 1×102, in carbon fibres type IM, in spite of an increase of
Young's modulus
, 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.
Source:
PAC, 1995, 67, 473. (Recommended terminology for the description of carbon as a solid (IUPAC Recommendations 1995)) on page 482 [Terms] [Paper]