TOUGH TEXTILE Nanocomp engineers demonstrate the company's large-format carbon nanotube textiles. The U.S. Air Force is evaluating material for potential deployment in advanced electromagnetic interference (EMI) and electrostatic discharge (ESD) shielding systems on manned and unmanned aircraft. Image: © NANOCOMP TECHNOLOGIES, INC.
Aerospace and aircraft companies as well as the military have been challenged to find ways of effectively shielding sensitive electronic equipment such as radar and radios from electromagnetic interference (EMI) without adding a lot of weight to aircraft and satellites (the more massive they are, the more fuel they need to stay in the air or achieve orbit, respectively). Whereas EMI can lead to headaches like erased data and loss of connectivity for casual computer and cell phone users, the problem is far more serious in aircraft, where interference can jam cockpit radio and radar signals, preventing pilots from sending and receiving crucial information.
Looking to solve this problem on its manned and unmanned aircraft, the U.S. Air Force will by the end of the year to kick off an 18-month study of the use of carbon nanotube sheets to create a shielding layer on the surfaces of lightweight composites. Nanocomp Technologies, Inc., a Concord, N.H.–based maker of carbon nanotube materials, said last this week the Air Force selected the company as prime contractor for the second phase of a larger program intended to find a substitute for the nickel-based conductors currently used for electrostatic discharge (ESD) and EMI shielding.
EMI is the result of electromagnetic radiation given off by electronic devices interrupting an electrical circuit's performance, whereas ESD is the sudden and rapid transfer of an electrostatic charge. Nanocomp's carbon nanotube sheets are designed to act as a "Faraday cage" that can block out external static electrical fields from sensitive circuitry. Because the material can carry electricity, it redirects energy along its conducting plane rather than allowing electronic emissions to penetrate the protected area, the company says.
Although the Air Force will not formally award the contract to Nanocomp for a few weeks, the company, which successfully completed the program's initial phase earlier this year, is working to scale up volume and decrease the cost of its carbon nanotube–impregnated mats, which can be made as large as 1.2 by 2.4 meters, says Nanocomp CEO Peter Antoinette. Larger sheets allow for more surface area coverage, reducing the need for seaming or joining and other manufacturing-intensive assembly steps, he adds. Northrop Grumman Aerospace Systems and Cytec Engineered Materials are also expected to participate in phase two of this program.
The Air Force's testing of Nanocomp's sheets is just the latest example of its work with carbon nanotubes. The U.S. Air Force Research Laboratory's Materials & Manufacturing Directorate (ARFL/RX), based at Wright–Patterson Air Force Base in Dayton, Ohio, has been investigating applications for carbon nanotubes for at least the past decade, mixing them with polymers in search of stronger, lighter materials that could replace aluminum and even copper wiring, which can represent as much as a third of the aircraft's total weight.
Sheets of paper or fabric made from carbon nanotubes could prove useful for allowing satellites to safely manage static electricity while in space, particularly because there is no way to provide electrical grounding once they're in orbit, says Karla Strong, a materials engineer for the Thermal Sciences & Materials branch within the ARFL/RX. The branch's engineers research, develop and apply new technologies in an effort to prevent the large amounts of heat produced by increasingly powerful electrical and propulsion systems from damaging aircraft.