ABSTRACT
A common characteristic of the spun fibers, comprising 105-106individual CNTs, is their non-uniformity of cross sections, shown in Figure 14.2. Instead of the unit of GPa, Yuri is more often used to describe the tensile properties (strength and modulus) of such fibers, after Yuri Artsutanov who proposed the space elevator in 1960. Yuri is a unit by dividing the load by the linear mass density that is the mass (in grams) per kilometer fiber. One million Yuris (1 M Yuri) is somewhere between steel wire (0.5 M Yuri) and Spectra® 2000 fiber (3.5 M Yuri). It is also very common to use GPa cc/g or N/tex, both of which are equivalent to 1 M Yuri. The first reported direct-spun CNT
fibers in 2004 had the tensile strengths ranging from 0.05 to 0.5 N/ tex (equivalent to 0.10 and 1.0 GPa, assuming a density of 2.0 g/cc) [2]. The strength was improved to 0.7 N/tex [3], 2.2 N/tex [4], and a surprisingly high value of 9.8 N/tex measured with a gauge length of 1 mm [5] (Figure 14.3).
