Helping Strong Materials Take Wing

Credit: Photo by Walter Lee Olivares de la Cruz on Unsplash

Overwhelmingly, airline passengers prefer that the wings stay on the plane. And they do hang in there, thanks to decades of research into how materials such as aluminum can become damaged by various conditions and forces.

Now, however, airplanes and other structures are increasingly made of low-weight, high-strength composite materials: typically epoxy resins and fabrics reinforced with carbon fiber. (The Boeing 787 Dreamliner is about 50% composites by weight.) So there is intense interest in how and why composites may fail. Recently NIST scientists devised a way to see the earliest onset of fracture, in three dimensions, at the scale of individual molecules.

They made tiny test structures out of the sort of polymer often used in composites but doped the material with fluorescent molecules that emit light when excited. After applying stress that deformed the polymer, they excited the molecules and recorded the light given off. The pattern of emissions from the embedded fluorescent molecules provided a sort of lighted path revealing the direction of the deformation caused by stress.

The researchers expect that the novel technique will enable engineers to design even safer composite materials for airframes, wind-turbine blades, bioimplants such as knee replacements, and more, further increasing confidence that, no, the wings will not fall off.