It is a common practice to stretch out before exercise or some other physical labor for many reasons. In the case of carbon nanotubes, it is to make them stronger and better conductors, but stretching them is difficult. Researchers at North Carolina State University though have figured out a way to do it and it could lead to stronger and light composite materials
For things are needed for carbon nanotubes to be useful as a strong material. They have to be long, aligned, held together by a polymer or resin, and stretched out so they are straight. All of these improve the strength of the finished product, but accomplishing them all is tricky. The researchers did it though using rotating spools. Starting with a forest of long nanotubes, they pulled them down to align them before winding them on a spool. While being wound up, a polymer was applied to bind the nanotubes together. By pulling the nanotubes as a ribbon onto the rotating spool, they were able to stretch them and increase their tensile strength by 90% and stiffness doubled.
As this method achieves all four of the requirements for making strong carbon nanotubes for composite materials, it could allow for them to see greater use. As they can be stronger for their weight compared to other materials like steel, it could make many forms of travel much more efficient and/or safer from airplanes to bicycles.