Mechanical response of Ti–6Al–4V hierarchical architected metamaterials

Abstract

A snap-fit manufacturing technique has been designed for making hierarchically architected lattice structures from Ti–6Al–4V alloy sheets. By patterning the unit cell of a small-scale lattice along the struts of a self-similar unit cell of a large-scale lattice, fractal-like geometry with a hierarchy order of 2 was obtained. A subsequent vacuum brazing operation was performed to create fractal-like structures with an octahedron-of-octahedra half-cell geometry. Hierarchical architected lattices with a fractal number 4–15 and a relative density ranging from 0.7% to 12% have been manufactured by allowing a fixed small-scale cell size of approximately 10 mm and a varying large-scale cell size from 40 to 190 mm, and their mechanical responses under compression been experimentally examined. The measured compressive elastic moduli and strengths of the hierarchical lattices agreed well with micromechanical and finite element predictions. The Ti–6Al–4V hierarchical lattice materials exhibit very competitive mechanical properties when compared to other cellular materials, and provide a new solution for lightweight engineering materials for use at maximum service temperature up to 450 °C.