زكيه نظري

Bone tissue engineering, as a developing field, aims to create high-performance biological tissues for repairing damaged tissues. In this regard, the performance of temporary scaffolds depends on their biocompatibility, mechanical properties, and manufacturing methods. Three-dimensional printing technology serves as a key tool, enabling the layer-by-layer fabrication of complex scaffolds with adjustable porosity. In this thesis, the fracture behavior of bone scaffolds with Voronoi structures made of polylactic acid-chitosan was studied using experimental and numerical methods. The study examines the effects of irregularity, the relative density of polylactic acid, and crack length on the critical stress intensity factor in 90 bone scaffolds with Voronoi lattice structures. These scaffolds were fabricated using the fused deposition modeling technique, and chitosan was added to the void spaces of the scaffolds. The aim was to investigate the mechanical properties resulting from the combination of polylactic acid and chitosan. To eva‎luate the fracture toughness parameters, fracture tests were conducted on cracks with a zero-degree angle. Subsequently, the parameters of critical stress intensity factors (KIf and KIIf) were calculated using finite element analysis in Abaqus software, based on the maximum loads obtained from experimental tests. The results showed that an irregularity factor of 0.5, compared to an irregularity factor of 0, increases KIf by an average of 17%, indicating improved resistance to crack initiation and propagation. Conversely, an irregularity factor of 1, compared to 0, decreases KIf by an average of 14% due to stress concentration. Moreover, KIIf values increased continuously with greater irregularity, reflecting higher resistance to shear stress in more complex structures. The investigations revealed that higher relative density of polylactic acid leads to an increase in KIf but a decrease in KIIf, demonstrating a balance between material density and stress distribution. The study also found that as crack length increases, KIf and KIIf values also increase, emphasizing the significance of crack propagation in scaffold design.

داربست استخواني , پلي‌لاكتيك‌اسيد , كيتوسان , ورونويي , مدل‌سازي رسوب ذوب‌شونده , ضريب شدت تنش

bone scaffold , polylactic acid , chitosan , Voronoi , fused deposition modeling , stress intensity factor

Zakiye Nazari

Fathollah Taheri-Behrooz