Influence of density and loading speed on static and impact properties of closed-cell metallic foams

Currently, to reduce CO2 emissions and fuel consumption, the automotive industry seeks to replace high-density components with low-density ones. Due to their advantageous properties (high stiffness/strength-to-weight ratio and high energy absorption performances), metallic foams (MFs) are identified as ideal candidates for this purpose. This paper investigates the influence of density (0.3–1.0 g/cm3) and loading speed (1.74 mm/min – static to 174000 mm/min – impact) on the mechanical behavior of MFs. Studied MFs have closed-cells and are manufactured from aluminum alloys (AlMg1Si0.5 + 0.4 wt% Ti) through the powder metallurgy route. For this purpose, rectangular specimens with lateral notches and surface skin were used. A 3-point bending test was used for the static properties, while the instrumented Charpy hammer was adopted for the impact behavior. Following the experimental tests, a macrostructural analysis of the fracture surfaces of the specimens was performed to highlight the influences of the topology on the MF properties. It was found that both foam density and loading speed significantly influence their mechanical behavior. Significant increases in properties were obtained with the increase in foam density and test speed. Equations have been proposed that can predict with high-accuracy the main mechanical properties of MFs. It was observed that the mechanical properties of MFs are closely related to the topology of the fracture surface, as well as to the shape of the foam cells and the skin of the specimens.