Page 166 - Carbon Nanotube Fibres and Yarns
P. 166
Carbon nanotube yarn structures and properties 157
30 1
1.4
25
0.8
Yarn diameter (µm) 20 0.6 Yarn linear density (tex) Strength (GPa) 1.2 1
0.8
15
0.6
0.4
10
5 Diameter Linear density 0.2 0.4
0.2
0 0 0
0 5 10 15 20 0 20 40 60 80 100
(A) Specimen sequence number (B) Fiber length (cm)
Fig. 7.17 Variability of CNT yarn in a 1-m yarn length: (A) yarn diameter and linear
density [27], (B) yarn strength [42]. (Panel (A) reprinted with permission from M. Miao,
Electrical conductivity of pure carbon nanotube yarns, Carbon 49 (12) (2011) 3755–3761;
Panel (B) reprinted with permission from Y. Zhang, L. Zheng, G. Sun, Z. Zhan, K. Liao, Failure
mechanisms of carbon nanotube fibers under different strain rates, Carbon 50 (8) (2012)
2887–2893.)
Deng et al. [43] studied the strength distribution of a CNT yarn using
a modified Weibull strength distribution model. The modulus, strength, and
fracture strain of the yarn were in the ranges of 2–10 GPa, 82–490 MPa,
and 0.03–0.12, with the average values of 4.6 GPa, 170 MPa, and 0.068,
respectively. The modified Weibull model takes into account of yarn diam-
eter distribution:
σ m
F σ () =−1exp d − h (7.5)
σ d
where σ d = σ 0 L −1/m , L is the yarn specimen length, d is the yarn diameter,
h is a diameter dependent parameter, σ 0 is the scale parameter (characteris-
tic strength), and m is the Weibull shape parameter that is an indication of
the scattering of strength distribution. A larger value for the Weibull shape
parameter m indicates a narrower strength distribution (smaller scattering).
The shape parameter m was found to be 4.1 and the diameter-dependent
parameter h was 5.82. In comparison [44], the m values were 1.7 for CVD-
grown multiwalled CNTs, 4.5 for Thornel-300 carbon fibers tested at
60 mm gauge length, and 5.12 for glass fibers tested at 5 mm gauge length.
So the CNT yarn showed smaller scattering than those of multiwalled
CNTs but larger than those of commercial carbon and glass fibers.
Zu et al. [45] produced CNT yarns using the twisting and
solvent-densifying method [9]. The average strength, modulus, and strain
to failure obtained from 50 tensile tests were 1.2 ± 0.3 GPa, 43.3 ± 7.4 GPa,
and 2.7% ± 0.5%, respectively. They obtained a Weibull shape parameter m
of 5.44, higher than that determined by Deng et al. [43].
