Aircraft inspectors can turn off heaters

Compiled by Photonics Spectra staff

Aircraft manufacturers soon may not need large heaters or traditional infrared thermography techniques to detect internal damage in planes and other objects, thanks to a simple handheld device and heat-sensitive camera devised by scientists at MIT.

In recent years, aircraft manufacturers have built their planes from advanced high-strength fibers, such as carbon or glass, embedded in a plastic or metal matrix. Composites are stronger and more lightweight than aluminum but, when hit, often do not show surface damage even when internal damage has occurred. Inspectors currently use infrared thermography, which detects IR radiation emitted when the surface is heated.

Using a simple handheld device and a heat-sensitive camera, inspectors soon may be able to more efficiently inspect airplanes for damage, thanks to a new method developed by researchers at MIT.

In an advanced composite material, any cracks or delamination – separation into layers – redirects the flow of heat. That abnormal flow pattern can be seen with a thermographic camera. Although effective, the method is cumbersome because it requires large heaters to be placed next to the surface.

With the new approach, carbon nanotubes are incorporated into the composite material during production; when a small electric current is applied to the finished surface, the nanotubes heat up, eliminating the need for any external heat source. Using a thermographic camera or goggles, inspectors should be able to see the damage.

The technique could allow airlines to inspect planes more quickly, the scientists said. The project is part of a multiyear effort funded by the aerospace industry to improve the mechanical properties of existing advanced aerospace-grade composites. The US Air Force and US Navy both are interested in the technology, and the MIT team is working with them to develop it for their aircraft and vessels.

The new MIT carbon nanotube hybrid materials have thus far shown better mechanical properties, such as strength and toughness, than existing advanced composites. Findings appeared March 2011 in Nanotechnology (doi: 10.1088/0957-4484/22/18/185502).