carbon fibres type UHM

initialism: UHM
https://doi.org/10.1351/goldbook.C00837
Carbon fibres type UHM (ultra-high modulus) designates a class of carbon fibres having very high values of Young's modulus larger than \(600\ \rm{GPa}\) (i.e. greater than $\pu{55\%}$ of the theoretical \(C_{11}\) value of graphite).
Source:
PAC, 1995, 67, 473. (Recommended terminology for the description of carbon as a solid (IUPAC Recommendations 1995)) on page 482 [Terms] [Paper]