Porosity-dependent mechanical response of PLA Voronoi scaffolds under quasi-static and impact loading

Tissue engineering scaffolds play a vital role in bone repair by replacing affected bone regions and accommodating tissues for new bone formation. Additive manufacturing has opened pathways to mimic bone microstructures and tailor scaffold properties according to specific defect sites. In this study, we focussed on the suitability of Voronoi lattice scaffolds with different porosity levels (45 %, 55 % and 65 %) and build orientations for load-bearing bone regions, with special emphasis on assessing their performance under low-velocity impact conditions. Fused deposition modelling (FDM) technique was utilised for manufacturing scaffolds with polylactic acid (PLA) as the feedstock material. A lower printing nozzle temperature was selected to improve manufacturing quality. Key mechanical properties were found to decrease with increasing porosity under both quasi-static and impact loading. Under quasi-static loading, transversely built scaffolds showed lower yield strength and energy absorption. Interestingly, Young’s modulus exhibited opposing trends between transversely and horizontally built samples at lower and higher porosities. Yield strength under impact loading was higher at all porosities, indicating a positive influence of strain rate sensitivity. Whereas Young’s modulus decreased at higher porosities, indicating a shift in strain rate sensitivity from positive to negative. Overall, build orientation and loading rate had a noticeable effect on the mechanical properties. • Supportless PLA Voronoi scaffolds were successfully printed at 180 °C. • Strength and stiffness decreased with porosity under quasi-static and impact loads. • Transversely built samples had lower strength than horizontal ones under both loads. • Strain rate sensitivity shifted from positive to negative with increasing porosity.