Date of Defense
26-6-2026 9:30 AM
Location
Room 1043, F1 Building
Document Type
Thesis Defense
Degree Name
Master of Science (MS)
College
College of Engineering
Department
Mechanical and Aerospace Engineering
First Advisor
Abdelhamid Ismail Mourad
Keywords
Additive manufacturing, fused deposition modeling, infill geometry, layer height, fracture toughness
Abstract
This Additive Manufacturing (AM) has revolutionized modern design and manufacturing by enabling layer-by-layer fabrication directly from 3D Computer-Aided Design (CAD) models. This approach enhances material efficiency, reduces waste, and allows the production of complex geometries. Among various AM methods, Fused Deposition Modeling (FDM) is one of the most widely used techniques. In FDM, thermoplastic filament is heated and extruded through a nozzle to build components layer by layer. Several process parameters significantly influence the structural integrity, mechanical properties, and overall performance of FDM-fabricated parts. Recent research has increasingly focused on understanding the fracture behavior of commonly used materials such as Polylactic Acid (PLA) and Polyethylene Terephthalate Glycol (PETG), particularly under varying printing conditions. The aim of this study is investigating the influence of key FDM parameters including infill geometry and layer height on the Mode I fracture toughness of PLA and PETG. Four infill geometries (rectilinear, concentric, triangular, and cross hatch) and two layer heights (0.14 mm and 0.28 mm) were examined. The study objectives were to: (i) evaluate the impact of infill geometry and layer height on fracture toughness, (ii) analyze crack propagation behavior and microstructural characteristics, and (iii) provide a comparative assessment of PLA and PETG with recommendations for optimal design. Rectangular U-Notch specimens were fabricated using Bambu Lab 3D FDM-based printer, with a total of 48 specimens tested (16 configurations with three repetitions each). The results demonstrate that both infill geometry and material selection significantly affect the fracture performance. Layer height effect was minimal and insignificant. Concentric infill geometry exhibited the highest fracture resistance across all conditions, attributed to improved stress distribution along load paths. PLA showed higher strength than PETG. PLA performed well at 0.14 mm, whereas PETG demonstrated more consistent performance for both layer heights. Among different geometries, concentric provided the best performance, followed by cross hatch and rectilinear, while the triangular geometry exhibited the lowest fracture resistance.
Included in
Fracture Performance of FDM Printed PLA and PETG: Role of Infill Geometry and Layer Height
Room 1043, F1 Building
This Additive Manufacturing (AM) has revolutionized modern design and manufacturing by enabling layer-by-layer fabrication directly from 3D Computer-Aided Design (CAD) models. This approach enhances material efficiency, reduces waste, and allows the production of complex geometries. Among various AM methods, Fused Deposition Modeling (FDM) is one of the most widely used techniques. In FDM, thermoplastic filament is heated and extruded through a nozzle to build components layer by layer. Several process parameters significantly influence the structural integrity, mechanical properties, and overall performance of FDM-fabricated parts. Recent research has increasingly focused on understanding the fracture behavior of commonly used materials such as Polylactic Acid (PLA) and Polyethylene Terephthalate Glycol (PETG), particularly under varying printing conditions. The aim of this study is investigating the influence of key FDM parameters including infill geometry and layer height on the Mode I fracture toughness of PLA and PETG. Four infill geometries (rectilinear, concentric, triangular, and cross hatch) and two layer heights (0.14 mm and 0.28 mm) were examined. The study objectives were to: (i) evaluate the impact of infill geometry and layer height on fracture toughness, (ii) analyze crack propagation behavior and microstructural characteristics, and (iii) provide a comparative assessment of PLA and PETG with recommendations for optimal design. Rectangular U-Notch specimens were fabricated using Bambu Lab 3D FDM-based printer, with a total of 48 specimens tested (16 configurations with three repetitions each). The results demonstrate that both infill geometry and material selection significantly affect the fracture performance. Layer height effect was minimal and insignificant. Concentric infill geometry exhibited the highest fracture resistance across all conditions, attributed to improved stress distribution along load paths. PLA showed higher strength than PETG. PLA performed well at 0.14 mm, whereas PETG demonstrated more consistent performance for both layer heights. Among different geometries, concentric provided the best performance, followed by cross hatch and rectilinear, while the triangular geometry exhibited the lowest fracture resistance.