Effect of core structure on the quasi-static bending behaviors and failure mechanisms of aluminum foam sandwiches at elevated temperatures

In this study, a novel three-step method involving liquid casting, hot-rolling, and foaming was employed to fabricate three types of metallurgical bonded aluminum foam sandwich (AFS): AFS with a uniform foam core (UAFS), AFS with a density-graded foam core (GAFS), and AFS with an interlayer plate (IAFS). The bending behaviors of different AFS structures in four cases were investigated using the digital image correlation (DIC) technique to examine the effect of foam core structure, loading direction, and loading temperature. The results showed that the initial peak load (Fp), plateau load (Fpl) and load oscillation decreased with increasing loading temperature. IAFS demonstrated the low sensitivity to loading temperature, an important reason was the addition of interlayer plate. The deformation mode involved interface separation and foam core detachment occurring in the interface vicinity beneath the indenter at the lower temperatures (≤300 °C) shifted towards well-bonded interface and foam core densification at the higher temperatures (400 °C and 500 °C). Different core structures and loading directions gave rise to four distinct modes of crack initiation and propagation. In addition, as the loading temperature increased, the strain localization effect was diminished, accompanied by hindering in crack formation. The fracture mode of core shear transitioned from brittle to ductile with increasing loading temperature.