https://doi.org/10.1351/goldbook.C00834
Carbon fibres type HT are carbon fibres with values of Young's modulus between and to . The term HT, referring to high tensile strength, was early applied because fibres of this type display the highest tensile strengths.
Note: The disposition of boundaries between the fibre types is somewhat arbitrary. For carbon fibres type HT, the values of the strength-to-stiffness ratio are typically larger than . The tensile strength of carbon fibres is flaw-controlled, however, and therefore the measured values increase strongly as the diameter of the filaments is decreased.