Impact of Voronoi network irregularities and polymer infiltration on the stress intensity factor of 3D-printed bone scaffolds

Developing bone scaffolds with enhanced mechanical properties is critical for improving their performance in tissue engineering applications. This study explores the effect of Voronoi network irregularities and polymer infiltration on the fracture behavior of 3D-printed polylactic acid (PLA) scaffolds. PLA scaffolds of different relative densities (25 %, 40 %, and 100 %) and irregularity factors (0 to 1) were fabricated by fused deposition modeling and infiltrated with chitosan polymer. Finite element analysis, fracture tests, and digital image correlation techniques were carried out to determine the mixed-mode (I/II) stress intensity factors. It was found that a moderate irregularity coefficient of 0.5 significantly improved fracture toughness, with an improvement of 24.15 % compared to regular scaffolds. Scaffolds with a 40 % relative density possessed the optimal balance between strength and porosity, leading to a 43 % higher $K_{\mathrm{If}}$ than scaffolds of 25 % density. The research further illustrated that an increase in the crack length ratio escalates stress intensity factors, whereas excessive irregularities diminish structural integrity. Adding chitosan improved mode II fracture resistance, with $K_{\mathrm{IIf}}$ reaching its maximum at the highest levels of irregularity and crack length ratio.