Properties of metal foams

The characteristics of a foam are best summarized by describing the material from which it is made, its relative density, p/ps (the foam density, p, divided by that of the solid material of the cell wall, ps), and stating whether it has open or closed cells. Beyond this, foam properties are influenced by structure, particularly by anisotropy and by defects - by which we mean wiggly, buckled or broken cell walls, and cells of exceptional size or shape.

Metal foams are still inadequately characterized, but the picture is changing rapidly. An overview of the range spanned by their properties is given by Table 4.1 and the property charts of Section 4.3. The primary links between properties, density and structure are captured in scaling relations, listed in Section 4.4. They allow foam properties to be estimated, at an approximate level, when solid properties are known.

The producers of metal foams have aggressive development programs for their materials. The properties described here are those of the currently available generation of foams, and should be regarded as a basis for initial, scoping, calculations and designs. The next generation of foams will certainly be better. Final design calculations must be based on data provided by the supplier.

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