Mechanical behavior and failure mode of body-centered cubic, gyroid, diamond, and Voronoi functionally graded additively manufactured biomedical lattice structures

Given the capability to produce parts with complex geometries, powder bed fusion using a laser beam (PBF-LB), one of several additive manufacturing techniques, is becoming increasingly prevalent in both research and industry. Advances in the development of biomedical lattice structures show a trend in the use of functional gradients for greater customization and adjustment of mechanical properties according to the demands. This study analyzed four biomedical potential lattice structures (regular and graded) manufactured using PBF-LB in Ti6Al4V alloy. X-ray computed microtomography results demonstrated high accuracy for thin walls (0.6 mm), with negligible discrepancies. The diamond structure exhibited the highest mechanical resistance (∼130 MPa) and energy absorption (∼200 J) and showed a reduced effect of the gradient on the mechanical properties. The body-centered cubic (BCC) structure had the lowest resistance and absorption (∼6 MPa), but the use of graded structures improved energy absorption (∼30 J). Two primary failure modes were identified: shear fracture at 45° and crushing. Triply periodic minimal surface (TPMS) structures showed initial crushing before shearing. Graded structures experienced failures in the upper region due to lower density, causing stress and strain increases. Numerical simulations revealed stress distribution, with TPMS structures displaying better distribution and BCC/Voronoi structures having stress concentrators, contributing to lower collapse loads. Cross-sectional views indicated a tendency for 45° failure in regular structures and progressive collapse in graded structures.