Aluminum foam sandwich with density-graded open-cell core: Compressive and flexural response

We created a density-graded, open-cell, aluminum foam core sandwich (AFS) by joining, alternately arranged Al sheets and three different relative density (ρ* = 7%, 29%, and, 42%) foams using a zinc filler. A defect free, lamellar, α + η microstructure was observed in the foam/facesheet joint interface. Vickers microhardness and nanoindentation of the joint revealed higher hardness in the Zn filler compared to foam struts and sheets. The density-graded AFS showed a staggered compressive stress-strain response and its energy absorption increased by up to 607% compared to as-received (7% ρ*) foam core AFS. Three-point bend testing of the density-graded AFS showed indentation, foam strut bending, core shear and interface debonding as major failure mechanisms. Our results show that density-grading of foam core by introducing different relative density foam layers is a viable method to tailor the mechanical response of AFS.