I have at times made out the use of carbon nanotubes in fillers for composite resins as much a marketing ploy as it was a structural improvement.
It seems researchers of a joint research project between Applied NanoStructured Solutions LLC (ANS, Baltimore, Md.), a Lockheed Martin subsidiary, and Owens Corning (Toledo, Ohio) were not altogether satisfied either with just using carbon nanotubes in these fillers.
The researchers were frustrated that resin loading of the carbon nanotubes was limited to little more than 3% or else the filler would become to viscous. So instead they started to look for ways of using carbon nanotubes in reinforcements rather than resins.
Back in 2007 when they embarked on this project they were looking to develop a way to incorporate nanoparticles directly into the fibers themselves. Now they have done that and also managed to do it in a way that it can be dropped into composites processors.
“We have developed a way to grow carbon nanostructures on fabrics,” Dr. Tushar Shah, ANS’ chief technology officer, is quoted as saying in the article from Composites World. “We’re not making CNTs and then transferring them,” he clarifies. “This is a continuous, direct growth process, directly onto the reinforcing fibers.” The first application area being targeted is in electronics for electromagnetic interference (EMI) shielding. But that is really just a starting off point. Because the composites developed with this process exhibit an inherent conductivity they are likely strong candidates for structural health monitoring (SHM) applications in which the material itself could serve as an in situ nanosensor in “smart” body armor. If this industrial partnership is successful in getting these composites into more products, I think my reflex to scoff at the use of carbon nanotubes in them will have been cured.
Dexter Johnson is a contributing editor at IEEE Spectrum, with a focus on nanotechnology.