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Cradle-to-Grave Safety Testing of Aircraft Composites

Professor Kosmatka with his students
Professor John Kosmatka works with his graduate students to install a Predator wing in the new Composite Aviation Safety Center.

Predator wing
Researchers will be working on two Predator wings.

Detecting damage to the outer skin and primary structural components of aircraft is becoming increasingly difficult as manufacturers switch from aluminum alloy to composite materials, which can undergo damage that is not visible to the naked eye.

Because a single hit is unlikely to have significant consequences, researchers at the Jacobs School are working to better understand how repeated and widespread impacts, as well as other kinds of severe events affect the aircraft's compostite materials over their lifespan.

A major facility in the new Structural and Materials Engineering building is dedicated to studying all aspects of full-scale composite material aircraft structures. In the Composite Aviation Safety Center, researchers build and test specimens representing aircraft parts made from composite materials. They outfit these specimens with sensors and use the data they collect to build computational models to predict damage – all in an effort to make composite structures safer and more efficient.

"What makes us unique is that we will be researching the entire product development process," said John Kosmatka, a professor of aerospace and structural engineering and one of the lead researchers for the new facility.

Kosmatka and colleagues Hyonny Kim and Chiara Bisagni, in the Department of Structural Engineering, focus on manufacturing and testing. One of Kosmatka's projects investigates how carbon nanotubes could reinforce the composite's resin matrix. The ultimate goal is to develop a custom-tailored nanoparticle to reinforce the resin matrix as well as a procedure to place these high-performance particles in critical stress regions.

Meanwhile, Kim's lab subjects components to a wide range of tests to simulate impacts and dynamic loading, including everything from hail to cargo loaders. Prior to testing, structures can be outfitted with embedded sensors and damage detection strategies developed in the lab of Michael Todd, a professor of structural engineering. The sensors use ultrasonic waves to detect damage, from cracks, to voids, to corrosion. Damage also can be detected by special instruments placed on the outside of the structures and developed in the lab of structural engineering professor Francesco Lanza di Scalea. His team is using ultrasonic waves to detect and quantify damage, both during and after testing, or after an actual event, such as a crash.

Test: time=1.396ms Test: time=1.529ms Test: time=1.795ms Test: time=2.261ms Test: time=3.458ms
The lab of Professor Hyonny Kim simulated the impact of hail on composite materials used in modern jets. Researchers launched ice spheres of about 2.4 inches in diameter at 108 meters per second using a gas gun built for testing ice impacts on aircraft structures. Their target was a 12" by 24" composite panel made of the same composite material used in the Boeing Dreamliner. The panel is about 12 times thicker than an aluminum soda can (0.064 inches). The research was funded by the Federal Aviation Administration. Learn more Feb. 28, 2013 at an alumni event with Kim at Boeing in Seal Beach, Calif. (See details.)

Finally, the data collected during the tests comes back to Kosmatka's lab, where he and structural engineering professor Joel Conte are developing probabilistic-based computational models to predict the type and growth rate of damage in composite aircraft parts. These computational models, along with an extensive experimental database, aim to predict the remaining life of in-service aircraft components, as a result making it easier to schedule maintenance, or provide a critical warning to the flight crew.

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