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.
Source:
PAC, 1995, 67, 473
(Recommended terminology for the description of carbon as a solid (IUPAC Recommendations 1995))
on page 481
Cite as:
IUPAC. Compendium of Chemical Terminology, 2nd ed. (the "Gold Book"). Compiled by A. D. McNaught and A.Wilkinson. Blackwell Scientific Publications, Oxford (1997). XML on-line corrected version: http://goldbook.iupac.org (2006-) created by M. Nic, J. Jirat, B. Kosata; updates compiled by A. Jenkins. ISBN 0-9678550-9-8.
doi:10.1351/goldbook.