Engineers predict that future aircraft will have high-tech "smart" skin--a network of sensors embedded in wings or doors to warn of impending failures or to assess structural damage from enemy fire. But developing devices sensitive enough to pick up tiny changes and remain free from the electrical interference prevalent in planes isn't easy to do.Now, in one of the few unclassified experiments using military planes, researchers at Virginia Tech's Fiber & Electro-Optics Research Center have demonstrated a fiber-optic device that may do the trick. In their sensor, light shines through one optical fiber, then bounces off the end of another a few microns away. As a wing changes shape under strain, the gap between fibers grows or shrinks, altering the interference pattern between the original beam and the reflected light.
When Virginia Tech researchers mounted the devices on the wing of an F-15 fighter at Wright Patterson Air Force Base, the fiber-optic sensors proved to be at least 10 times more sensitive than conventional electrical strain sensors.