US Patent 7947364 Energy-attenuation structure

An energy-attenuation structure comprising a core layer of cellular material. Substantially most of the cells of the cellular material are open cells, with those cells disposed in the central portion of the core layer being more open than are those cells disposed in outer portions of the core layer. The openness of the cells generally decreases from the interior of the core layer in a direction toward the outer portions. At least some of the cells of the core layer are filled with a liquid.