EXPERIMENTAL EVALUATION OF HIERARCHICAL FUNCTIONALLY GRADED LATTICES USING DIGITAL IMAGE CORRELATION AND MICRO-CT

Hierarchical meta-materials based on functionally-graded lattices (FGLs) have the benefit of customizable material properties. However, the effects of sharp transitions on the effective properties of FGLs have yet to be evaluated. This experimental study focused on characterizing the compressive properties of hierarchical FGLs built with smooth or sharp gradings. A total of 12 samples were 3D-printed in Ti-6Al-4V alloy and tested in axial compressive loading. Digital image correlation (DIC) was used to measure displacements and deformations. The 3D-printing quality of FGLs was also evaluated by micro-CT imaging of 5 samples. The results showed that the cross-sectional areas of struts in FGLs with sharp transitions were 26% smaller than uniform lattices and FGLs with smooth transitions. Compression testing also confirmed a lower average elastic modulus in FGLs with sharp gradings. These results will provide insights for incorporating adjustment factors to account for the loss of strength in FGLs.