Post-yielding and failure mechanism of additively manufactured triply periodic minimal surface lattice structures

This study investigates the post-yielding and failure mechanisms of additively manufactured Triply Periodic Minimal Surface (TPMS) lattice structures, including Primitive, Gyroid, Diamond, and Neovius. Experimental compression tests were conducted on Ti-6Al-4V samples made using the laser powder bed fusion process. In addition, numerical simulations were performed incorporating the modified Mohr-Coulomb damage criterion to analyze mechanical responses, deformation patterns, and local stress states. Numerical results revealed significant improvement in accuracy with damage consideration, especially for post-yielding prediction. The error of predicted energy absorption could be reduced by up to 80 % when the damage model was included. In addition, the results revealed a transition in failure modes from buckling to ductile damage at a relative density of approximately 0.3. This observation was emphasized by the analysis of stress triaxialities, which exhibited small changes when the relative density was greater than 0.3. Furthermore, under the same mass, the Diamond structure provided the highest energy absorption. However, under the same maximum allowable stress, the Gyroid exhibited the highest absorbed energy. It was also found that TPMS Ti-6Al-4V could be designed to achieve extensive ranges of specific energy absorption, approximately from 10-4 to 10-3 J/g. These findings offer valuable insights into TPMS lattice structure behavior and emphasize the significance of considering a ductile damage model for accurate numerical predictions.