Influence of Infill Geometry and Material Type on the Mechanical Performance of FDM-Printed PLA, PLA Wood, and PETG Components

Additive manufacturing (AM) using fused deposition modeling (FDM) enables the fabrication of lightweight polymer components with tailored mechanical properties. However, the combined influence of material type and infill architecture on mechanical performance remains insufficiently understood. This study investigates the effects of three infill geometries (Concentric, Cubic, and Gyroid) and three thermoplastic materials (PLA, PLA-Wood, and PETG) on the tensile, flexural, and compressive behavior of FDM-printed specimens fabricated at 70% infill density. Mechanical testing was performed according to ASTM D638, ASTM D790, and ASTM D695 standards, and the results were analyzed using the Taguchi method. The Concentric pattern produced the highest tensile strength and modulus across all materials, with improvements of up to 45% compared with Cubic and Gyroid structures. Cubic exhibited the highest flexural modulus, while Gyroid and Cubic generally provided superior compressive strength due to enhanced load redistribution. Taguchi analysis identified material type as the dominant factor influencing mechanical performance, contributing 74.4, 91.1, and 77.1% of the variation in tensile, flexural, and compressive strengths, respectively. SEM observations revealed that fracture was governed primarily by interlayer delamination, void-assisted crack propagation, and interfacial debonding. The results demonstrate that infill architecture governs load-transfer mechanisms, whereas material selection exerts the strongest influence on overall mechanical performance. These findings provide practical guidelines for optimizing FDM-printed structures for lightweight engineering and biomedical applications.