X-Ray Study of Low-Density Materials

It's hard to get an X-ray image of low-density material like tissue between bones because X-rays just pass right through like sunlight through a window. Sandia studies myriads of low-density materials, from laminate layers in airplane wings to foams and epoxies that cushion parts. So they borrowed and refined a technique from the medical field, X-ray phase contrast imaging, to look inside the softer side of things. The technique measures not just the number of X-ray photons that get through the sample, as in conventional X-ray imaging, but also the phase of the X-rays after they pass through, offering a complete look at interfaces inside a structure.