In recent years, many airplane manufacturers have started building their planes from advanced composite materials, which consist of high-strength fibers such as carbon or glass, embedded in a plastic or metal matrix. Such materials are stronger and more lightweight than aluminum, but they are also more difficult to inspect for damage because their surfaces usually don't reveal underlying problems.

“With aluminum, if you hit it, there's a dent there,” says Brian L. Wardle, associate professor of aeronautics and astronautics. “With a composite, oftentimes if you hit it, there’s no surface damage, even though there may be internal damage.”

Wardle and his colleagues have devised a new way to detect that internal damage using a simple handheld device and heat-sensitive camera. Their approach also requires engineering the composite materials to include carbon nanotubes, which generate the heat necessary for the test.

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