Additively-manufactured lattice-grid sandwich cylinders and elastoplastic multi-failure analyses

Abstract

Aluminum alloy lattice-grid sandwich cylinders, comprising a symmetric pyramidal truss core and open grid face-sheets, are additively manufactured using the selective laser melting method. The compression behaviors of these sandwich cylinders are investigated. Failure is controlled by three competing mechanisms: global buckling, core shear instability and grid buckling, with the active failure mode determined by the cylinder geometry and the material yield stress. Failure criteria are defined in terms of the effective elastoplastic properties of the grid-skins and core, which agree well with the measured and simulated failure responses, and are applied to generate multi-failure maps with cylinder geometrical parameters as axes. The maps help with failure load prediction and design optimization. For these cylinders, grid buckling is proposed as the dominant failure mode.