Computer Simulation and Experimental Approach in the Investigation of Deformation and Fracture of TPMS Structures Manufactured by 3D Printing

Because of the developed surface of the Triply Periodic Minimum Surface (TPMS) structures, polylactide (PLA) products with a TPMS structure are thought to be promising bio soluble implants with the potential for targeted drug delivery. For implants, mechanical properties are key performance characteristics, so understanding the deformation and failure mechanisms is essential for selecting the appropriate implant structure. The deformation and fracture processes in PLA samples with different interior architectures have been studied through computer simulation and experimental research. Two TPMS topologies, the Schwarz Diamond and Gyroid architectures, were used for the sample construction by 3D printing. ANSYS software was utilized to simulate compressive deformation. It was found that under the same load, the von Mises stresses in the Gyroid structure are higher than those in the Schwartz Diamond structure, which was associated with the different orientations of the cells in the studied structures in relation to the direction of the loading axis. The deformation process occurs in the local regions of the studied TPMS structures. Maximum von Mises stresses were observed in the vertical parts of the structures oriented along the load direction. It was found that, unlike the Gyroid, the Schwartz Diamond structure contains a frame that forms unique stiffening ribs, which ensures the redistribution of the load under the vertical loading direction. An analysis of the mechanical characteristics of PLA samples with the Schwartz Diamond and Gyroid structures produced by the Fused Deposition Modeling (FDM) method was correlated with computer simulation. The Schwarz Diamond-type structure was shown to have a higher absorption energy than the Gyroid one. A study of the fracture in PLA samples with various cell sizes revealed a particular feature related to the samples’ periodic surface topology and the 3D printing process. Scanning electron microscopic (SEM) studies of the samples deformed by compression showed that with an increase in the density of the samples, the failure mechanism changes from ductile to quasi-brittle due to the complex participation of both cell deformation and fiber deformation.