Micromechanical Characterization of Metal Foams

Abstract

Cellular materials such as foams, honeycombs, or auxetic structures are an interesting type of structural materials for lightweight constructions or dynamic energy absorbers. These microheterogeneous materials consist of a hierarchical structure. Foams can be separated into a macro scale, meso scale, and micro scale dealing with the entire specimen or component, individual pores, and individual struts, respectively. As a result, the macroscopic foam properties are strongly related to the mesoscopic and microscopic properties as a superposition of geometrical structural response and material properties. Whereas the geometry can be easily determined, e.g., by computer tomography measurements, the evaluation of real micro material properties of individual struts or cell walls is still a very challenging task. The material properties of these constituents of open‐cell or closed‐cell foams significantly differ from bulk material properties due to changes in boundary condition during production and different scaling effects, such as different surface‐to‐volume ratios of oxide layers or different cooling conditions due to less material in struts than in the bulk. However, the need for reliable micro material properties for the realistic forecast of macroscopic properties of components made of foam by numerical simulations makes the micromechanical characterization and testing of metal foams to an emerging field of research. The present contribution deals with the most relevant achievements in the field from the beginnings to the present day.