Evaluating flexural response of additively manufactured functionally graded surface-based lattice structured cantilever beams

Nature has evolved over several billion years, optimizing structural efficiency through the use of repeating unit cells called lattice structures that have inspired researchers in mimicking such changes in real-life applications to achieve customized objects with high strength-to-weight ratios. Through additive manufacturing, such changes can be incorporated into designs providing site-specific properties enhancing mechanical performance while reducing weight. In this study, functionally graded lattices involving relative density and period change (mathematical parameters defining unit cell morphology) were designed from the fixed end to the loading end using three different triply periodic minimal surface (TPMS) structures, namely Gyroid, Schwarz-P, and Schwarz-D, for a cantilever beam. The structures were designed in a rectangular-shaped cantilever beam and additively manufactured using MultiJet fusion (MJF) technology. Flexure tests were performed on the manufactured samples using specially designed cantilever beam equipment until failure to study flexure properties. In calculating the flexural properties, the moment of inertia (MOI) of the beams plays a significant part which was also found by different methods owing to limitations, and a comparison is given between how the values vary when compared by taking the MOI of the bounding box. The experimental results indicate a decrease in mechanical properties as the period of the structures is changed. Even though the properties are enhanced as a result of better distribution in the case of period change in two directions, it is not as good as variation with linearly varying thickness. In the case of structures, the Schwarz-D structure performs the best among all the structures due to better tension and compression properties, as supported by the literature. Lastly, the failure of the structures reveals that as the period changes, the structures develop areas of stress concentrations that lead to earlier failure.