The effect of design parameters on the mechanical performance and energy absorption behavior of additively fabricated triply periodic minimal surface structures

Abstract In this study, the mechanical performance of triply periodic minimal surface (TPMS) structures under compression load, which are widely used in biomedical applications, was systematically investigated. The aim of the study was to compare the mechanical strength, energy absorption and surface-to-volume ratio of structures fabricated with different TPMS types (diamond, gyroid, primitive), volume fractions (40%, 60%, 80%) and layer thicknesses (0.10 mm, 0.15 mm, 0.20 mm) to determine the optimum fabrication parameters. Specimens fabricated with FFF, an additive manufacturing process, were subjected to compression tests. Additional tests were also carried out to elaborate the effect of layer thickness. The results were evaluated in terms of first peak, maximum force, energy absorption (EA), specific absorbed energy (SAE) and surface/volume (S/V) ratio changes and optimizations were made by Taguchi method. The novelty of this study is that it examines the combined effects of TPMS type, layer thickness, and volume fraction on the mechanical and energy absorption behavior of biodegradable polymer-based TPMS structures and determines the optimal parameters. Accordingly, fabrication parameters and geometric configurations were effective on failure behavior. Diamond specimens exhibited superior performance in terms of mechanical properties and energy absorption characteristics, while the performance of primitive specimens was relatively weak. The decrease in layer thickness resulted in significant increases in mechanical and energy absorption performances. The most effective parameter on the S/V ratio variation was volume fraction. There were dramatic decreases in S/V ratios with increasing volume fraction. It is recommended to prefer diamond or gyroid TPMSs with high volume fraction for applications such as bone implants where high strength is required. In applications such as tissue grafts where cell and fluid transfer are more important than mechanical strength, it is more feasible to increase the porosity by reducing the volume fraction. In applications where high mechanical strength and high porosity are required together, the desired properties may be achieved by reducing the layer thickness.