Multivariable assessment of ınfill strategies for enhanced mechanical properties in 3D-printed curved beams

Purpose This study specifically focuses on low-to-medium infill densities where the influence of internal geometry on structural performance becomes most dominant. This study aims to explore how different infill patterns and densities affect the mechanical response of curved-axis beams produced by fused filament fabrication-based additive manufacturing (AM), providing insights for optimizing lightweight and material-efficient components subjected to bending loads. Design/methodology/approach Twenty-seven PLA-based specimens with varying curvature radii (500, 750 and 1000 mm), infill patterns (grid, triangular and trihexagonal) and densities (20%, 30% and 40%) were manufactured. Each was subjected to three-point bending tests following ASTM standards. The experimental approach focused on analyzing force-displacement behavior to evaluate stiffness, load capacity and deformation characteristics under static loading conditions. Findings Increasing infill density enhanced the maximum force capacity of curved beams but reduced their displacement tolerance, reflecting greater rigidity. The trihexagonal (TH) pattern exhibited the highest displacement values, confirming its energy absorption capability, while the triangular (TA) pattern provided the greatest rigidity with lower deformation. The grid (GR) pattern showed intermediate behavior, with displacement capacity strongly influenced by curvature radius. Straighter beams generally displayed reduced displacement and higher stability, while more curved beams exhibited greater deformation. These results highlight the critical role of infill geometry and curvature in balancing strength, stiffness and energy absorption in three-dimensional (3D)-printed curved beams. Originality/value Unlike prior studies that focus on high or near-solid infill levels, this work uniquely highlights the mechanical response of additively manufactured curved beams within the low-to-medium infill density range, where infill geometry plays a critical role. The study presents the first detailed comparison of how infill strategies interact with curvature in 3D-printed beams. It delivers practical design guidance for engineers working with curved structures in mechanical, aerospace and civil applications. Its novelty lies in demonstrating how trihexagonal patterns can optimize performance across various geometries, supporting enhanced structural resilience in AM.