Airplane manufacturers have been changing over from aluminum to advanced composite materials. These lighter, stronger composites are made of fibers of carbon or glass embedded in a second material, often plastic.

One advantage is that composite-based planes use significantly less fuel. But there’s an important disadvantage. When aluminum is hit, you can see a dent. Composites, though, spring back to the original shape, which could hide internal damage.

One technique to test composite material takes advantage of heat transfer. Inspectors place large heaters next to a section of the plane. Any cracks will alter the flow of heat, and these changes can be picked up with a heat-sensitive camera. But this involves bulky and expensive equipment.

Now M.I.T. researchers have designed a new system. All you need is carbon nanotubes included in the composite, because nanotubes will heat up in response to a small electric current. This can be produced with a handheld device. Any internal deformations will still change the heat flow, which can be picked up by the thermal camera. The research was published in the journal Nanotechnology. [Roberto Guzmán de Villoria et al., "Multi-physics damage sensing in nano-engineered structural composites"]

This technique offers the ability to detect very small cracks—which could help keep passengers safer in the skies.

—Cynthia Graber

[The above text is an exact transcript of this podcast.]