Carbon fibres type
UHM (ultra-high modulus) designates a class of carbon fibres having very high values of Young's modulus larger than 600 GPa (i.e. greater than 55% of the theoretical C11 value of graphite).
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)