Engineering design with cellular metals. From mechanical properties to the implementation as car seat components

Despite the unique properties of cellular metals in terms of energy absorption and damping capacity and stiffness to weight ratio, their application in technical products is still limited. This can be attributed to (i) a large scatter in material properties for some metal foam products and (ii) a lack in standardization of testing procedures and design concepts devoted to cellular metals. For the example of safety-relevant car seat components, the present paper outlines the definition of material requirements, the selection of suitable metal foam components and the applied materials characterization methods. By means of compression, tensile and bending testing as well as light microscopy (LM) and scanning electron microscopy (SEM) of several candidate materials, i.e., Alulight and Alporas metal foam, as well as aluminum/aluminum foam and steel/aluminum foam sandwich structures, the general material properties and the reproducibility of mechanical data were tested. The results, which also include optical 3D strain distribution measurements, were used as input data for the design of structural car seat components using finite element calculations implying the simulation of the crash behavior. A further objective of the work is the derivation of robust and reliable mechanical testing procedures and an improved understanding of the damage mechanisms of cellular metals under monotonic loading conditions. Based on the international standard (ISO/DIS 13314) for compression testing of cellular metals, evaluation work for a standard for tensile testing has been started and is part of the present paper.