Wood-metal hybrid foam can be used for lightweight construction

Researchers at the Fraunhofer Institute for Wood Research, Wilhelm-Klauditz-Institut developed a hybrid foam material made of wood and metal.

Earlier, the researchers started developing foams from pure wood. The natural adhesive properties of wood make synthetic adhesives superfluous. The wood foam can be used for a whole range of applications, like a core material for lightweight construction and sandwich panels, as packaging material, or for thermal insulation or soundproofing.

To extend the range of applications, the researchers looked to combine wood foam and metal sponges. “Strengthening the wood foam with a metal skeleton, for example, can substantially enhance its characteristically low bending strength,” they say.

The process of making the foam was a little more complicated than just mixing metal and wood in a bowl. Rather than foaming the metal, the researchers cast it in an open-cell structure with many tiny cavities. The wood foam, “which has a firm consistency similar to that of beaten egg whites”, is then inserted into the metal sponge plate using a tapping technique.

The bending strength of the hybrid is even greater than that of its two components separate. This makes it an ideal core material for, for instance, sandwich panels.

Another advantage is that, unlike wood, metal can conduct electricity. The properties of wood foam are its high levels of sound absorption and low thermal conductivity, making it an excellent insulation material. Combining metal sponge and wood foam creates a lightweight hybrid material with a higher functionality, one that can be used for components that provide reinforcement and absorb sound.

The material is suitable for use in the automotive industry, for example, as reinforcing acoustic mats or as floor plates.

Photo: Fraunhofer Institute for Wood Research, Wilhelm-Klauditz-Institut