Researchers have improved techniques for spinning fibers of carbon nanotubes: they make the nanotubes align in the fiber, creating fibers as strong as, or stronger than, materials such as Kevlar that are used in bullet-proof vests. Also, the nanotube fibers, unlike regular ropes, can be knotted without hurting their strength much.
Alan Windle, a professor of materials science at the University of Cambridge, in England, made and tested the new nanotube fibers along with researchers at the Natick Soldier Research Development Center, in Massachusetts. Windle and his colleagues tugged on the nanotube fibers, finding that the weaker ones snapped at stresses around one gigapascal, making them comparable to steel, gram for gram.
The better-performing carbon-nanotube fibers broke at around six gigapascals, beating the strengths that manufacturers report for materials used in bullet-proof vests, such as Kevlar. These nanotube fibers matched the highest reported strengths for a couple of the strongest commercially available fibers, Zylon and Dyneema, also used in bullet-proof vests. A lone, extremely strong nanotube fiber was off the charts, reaching nine gigapascals of stress–far beyond any other reported material–before breaking. Earlier work with carbon nanotubes has produced fibers that withstand at most three gigapascals.