Page 178 - Carbon Nanotube Fibres and Yarns

Carbon nanotube yarn structures and properties 169

Fig. 7.21 Sonic and quasistatic moduli of twisted carbon nanotube yarns. (A) Sonic
and quasistatic moduli of the twisted carbon nanotube yarns and (B) the ratio be-
tween sonic modulus (E s ) and quasistatic modulus (E qs ) [69]. (Reprinted with permis-
sion from M. Miao, Characteristics of carbon nanotube yarn structure unveiled by acoustic
wave propagation, Carbon 91 (2015) 163–170.)

tenacity, dynamic, and quasistatic moduli and modulus ratio (E s /E qs ), as
shown in Table 7.2. The increase of the modulus ratio may be explained by
the added friction between the three plies of singles yarns in the structure.
On the other hand, gamma-irradiation treatment of twisted CNT yarn
in air introduces CNT-CNT cross-linking, which increases the yarn sonic
and quasistatic moduli and reduces the tendency of frictional slippage be-
tween the CNTs, leading to a decrease of the modulus ratio. Rub-densified
CNT yarns have high degree of CNT alignment and intimate CNT-CNT
contact because of the twistless yarn structure and the high CNT packing
density, resulting in much higher quasistatic and sonic moduli and a very
low modulus ratio as the nanotubes in the yarn are prevented from relative
movement.

Table 7.2 Dynamic and quasistatic tensile properties of CNT yarns [69].

Quasistatic Specific modulus (N/tex) Modulus
tenacity (cN/tex) Quasistatic Sonic ratio (E s /E qs )
Twisted singles 74.3 14.8 37.5 2.5
yarn
3-ply twisted yarn 50.5 8.1 22.4 2.8
Gamma-irradiated 87.7 26.1 58.1 2.2
twisted yarn
Rub-densified yarn 72.9 56.7 69.4 1.2