This new nanotube composite materal is very tough, i.e. resists crack propagation. It is not necessarily very strong, for example plasticene is very tough, but not strong at all. Glass is very strong, but not very tough - it is brittle rather than ductile.

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A way of manufacturing long chemically-bonded nanotube fibers that possess incredible strength has yet to be invented. Other super-strong super-fibers are often polymer strands with alternating monomer components, such as Zylon: ZYLON consists of rigid-rod chain molecules of poly(p-phenylene-2,6-benzobisoxazole) or PBO for short.

Speculative: Since really long nanotubes fibers are difficult to produce, I wonder if they can be linked together by another type of material into a chain molecule like PBO above? Maybe a bioreactor could produce these chains by protein synthesis?