Stress Distribution Analysis in 3D Printed PLA Brackets under Static Loading Conditions

Additive manufacturing enables rapid prototyping and low-volume production of structural components, yet the anisotropic mechanical properties arising from layer-by-layer deposition create stress distribution patterns distinct from conventionally manufactured parts. This research presents a comprehensive analysis of stress distributions in polylactic acid brackets fabricated through fused deposition modeling under controlled static loading conditions, investigating the influence of print orientation and infill pattern on mechanical performance and failure characteristics. Bracket specimens were fabricated using a commercial desktop 3D printer with three print orientations (XY-flat, XZ-edge, and ZX-vertical) and two infill patterns (grid and honeycomb) at 50% density. The experimental program was conducted at the Materials Testing Laboratory of Berlin Institute of Technology between February and September 2023. Static loading tests applied forces up to 500 newtons through a standardized fixture while strain gauge rosettes captured surface strain distributions at critical locations identified through preliminary finite element analysis. Results demonstrated that print orientation exerted dominant influence on stress concentration patterns, with XY-flat orientation achieving the most favorable stress distributions and highest ultimate failure loads averaging 338 newtons compared to 256 newtons for XZ-edge and 192 newtons for ZX-vertical orientations. Honeycomb infill patterns reduced maximum von Mises stress by 12.4% compared to grid patterns while maintaining equivalent structural stiffness within measurement uncertainty. Finite element predictions correlated with experimental measurements within 8.7% across all test configurations. The findings provide quantitative guidance for designers selecting print parameters for load-bearing PLA brackets, establishing that orienting the primary load path parallel to deposited layers minimizes stress concentrations at layer interfaces where crack initiation typically occurs. The validated finite element modeling approach enables preliminary optimization of bracket geometry prior to physical prototyping.