Improvement of crashworthiness in ultra lightweight metallic foam by heat-treatment for microstructural modification of base material

It is very important to understand the strain rate dependence of the platea u stress or the impact energy for the applications to a suitable design of automotive components. Limited data are, however, available for the mechani cal response of metallic foams under dynamic loading in comparison with pol ymer foams. In this study, the mechanical response and absorbed energy of a n open-celled SG91A aluminum foam with the low relative density of 0.03-0.0 65 is evaluated at a dynamic strain rate in similar to 10(3) s(-1) order in compression by the split Hopkinson pressure bar apparatus. In order to inv estigate the effect of microstructure in the solid material, solution treat ment and aging are performed and then examined at the same dynamic strain r ate. As a result, mechanical strength and absorption energy for as-received and heat treated SG91A aluminum foams showed the strain rate dependence. T his dependency was clearly decreased by the heat treatment. This mechanical response directly affects the energy absorption: the strain rate dependenc e of absorption energy is weakened with enhancing the ductility in solid ma terials by the heat treatment. Therefore, it is possible to control the abs orption energy of the metallic foam by the modification of its microstructu re, which affects the ductility in the solid material.