Sensors Detect Unseen Aircraft Damage
Commercial jets log hundreds, even thousands, of miles every day, and the relentless schedule of takeoff, touchdown, and turn around to do it again takes a toll on the aircraft. Airlines regularly perform spot maintenance checks, and every year or so, planes are taken out of service for extensive component testing. Dr. Kara Peters, associate professor in the Department of Mechanical and Aerospace Engineering, says the need for such scheduled maintenance would be less if aircraft were designed so the structural integrity of the fuselage and wings could be continuously monitored.
"As material systems change, we have to change how we inspect aircraft to ensure travelers' safety."
Such real-time monitoring is more difficult as planes switch from metallic bodies to parts made of carbon composites, Peters says. Metal fatigue usually begins as cracks in rivets, making it easy for mechanics to spot. "The problem with composites is that they dissipate the energy of impacts internally," she says. "The damage spreads inside out." Aircraft mechanics occasionally use imaging scans to look into composite parts, but Peters says fiber-optic sensors would improve monitoring. Hundreds of sensors could be placed on a single fiber and embedded inside the composite material. A monitor attached to the strand could then alert the flight crew or maintenance personnel to anomalies that indicate damage, so it could be repaired quickly. "If the monitoring shows nothing is wrong," she says, "you wouldn't need to park a plane as often for scheduled maintenance."
With funding from the Air Force, Peters is trying to optimize the sensor technology. While additional sensors provide more information, they also disrupt the structure of the composite material. "If you have enough sensors in there, you could produce an earlier failure in the part," she says. So, in her lab, she bangs on composites that contain various densities of optical fibers to see how much they can handle before they fail. That data is then used in computer simulations to determine the best layout for fatigue sensors in aircraft components.
Peters also is developing "healing mechanisms" within the composite parts, as part of a National Science Foundation grant, so damage can be repaired once sensors have identified it. She inserts resin that isn't fully cured in different regions of the composite matrix to determine whether chemically activating the resin would allow it to fill cracks and harden, preventing the damage from spreading. She also is working with Brigham Young University on ways to collect data from sensors faster, which would help with real-time monitoring. "As material systems change," she says, "we have to change how we inspect aircraft to ensure travelers' safety."