3. Energy absorption

Energy absorption is one of the preferred fields of application for cellular materials, and metallic foams in particular. Generally speaking, this involves taking advantage of the particular behavior of this type of material, highlighted by its highly characteristic compression curve (figure 1 ), which comprises three distinct zones:

• Zone 1 corresponds to normal material behavior in compression. Towards its end, it may include a peak, generally considered harmful, as it temporarily imposes a high level of stress;

• zone 2 is the specific and interesting zone of the curve. It corresponds to the successive collapse of the various foam cells, hence the sometimes irregular shape of the compression curve. This stress, which is almost...