Carbon Nanotubes Used to Stitch Materials Together

Engineers at Massachusetts Institute of Technology devised a method to use carbon nanotubes as a stitching material for composites. Because nanotubes could be made into some of the strongest known fibers, the technology should allow the development of new generation of medical prostheses and novel medical materials.

Wardle wondered whether it would make sense to reinforce the plies in advanced composites with nanotubes aligned perpendicular to the carbon-fiber plies. Using computer models of how such a material would fracture, “we convinced ourselves that reinforcing with nanotubes should work far better than all other approaches,” Wardle said. His team went on to develop processing techniques for creating the nanotubes and for incorporating them into existing aerospace composites, work that was published last year in two separate journals.
How does nanostitching work? The polymer glue between two carbon-fiber layers is heated, becoming more liquid-like. Billions of nanotubes positioned perpendicular to each carbon-fiber layer are then sucked up into the glue on both sides of each layer. Because the nanotubes are 1000 times smaller than the carbon fibers, they don’t detrimentally affect the much larger carbon fibers, but instead fill the spaces around them, stitching the layers together.
“So we’re putting the strongest fibers known to humankind [the nanotubes] in the place where the composite is weakest, and where they’re needed most,” Wardle said. He noted that these dramatic improvements can be achieved with nanotubes comprising less than one percent of the mass of the overall composite. In addition, he said, the nanotubes should add only a few percent to the cost of the composite, “while providing substantial improvements in bulk multifunctional properties.”

Press release: ‘Nanostitching’ could lead to much stronger airplane skins, more
Images: Top: Brian Wardle, the Charles Stark Draper Assistant Professor in the Department of Aeronautics and Astronautics, shows an advanced composite material held together by “nanostitching,” a technique developed at MIT that could make airplane skins and other products stronger. Side: Schematic showing carbon nanotubes bridging the gap between plies of an advanced composite.