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International audience; Metallic foam with uniform pore structure has been used as a filling material for the thin-walled tube to improve the structural crashworthiness. Homologous natural porous materials, such as bone, adopt graded pore structures and exhibit excellent performance. Inspired by the biological mechanism of adaptive remodeling in bone, this study proposes a density tailoring method on the foam filler to further improve the energy absorption of the composite structure. This method designs the density gradient of foam filler depending on the internal plastic strain distribution calculated by Finite Element (FE) analysis. The requisite material parameters of aluminum foam for the FE model, including the hardening curves and the plastic Poisson’s ratios, are obtained through experiments. The simulation results demonstrate that the outer part of foam filler exhibits a higher strain level than the inner part when adhesive effect is applied at the foam/tube interface. Radial density gradients are developed for the foam fillers to align with the FEA strain distribution pattern. The graded foam-filled tubes exhibit up to 24% higher specific energy absorptions (SEA) than the equal-weight uniform foam-filled tubes in FE simulations.

International audience; Radial graded structures in biological materials, e.g. bones, are lightweight and exhibit good mechanical properties. This paper developed a novel method to fabricate a functionally radial graded aluminum foam. In this method, a sequential solidification was applied from the periphery to the inner on the foaming aluminum melt to obtain a radial gradient. The graded foams were then served as fillers for thin-walled tubes. Quasi-static compressive tests were conducted on the foams and foam-filled tubes. The results indicated that the graded foam-filled tubes exhibited improved crushing resistance and specific energy absorption, compared to the uniform foam-filled tube with similar weight.