Geometry-driven hole-aware adaptive infill for improved tensile performance of FFF components

Fused Filament Fabrication (FFF) components exhibit pronounced mechanical anisotropy because filaments are deposited layer by layer along prescribed paths. This anisotropy becomes especially critical in components containing holes, where geometric stress concentration and interruption of load-oriented filaments coexist. This work proposes a geometry-driven hole-aware adaptive infill strategy that aligns deposition paths with the tensile load direction while locally deviating them to preserve path continuity around the hole. Infill lines are treated as virtual structural fibres, thereby reducing path interruption in the most critical region. A purely geometric algorithm based only on slicing information and load direction was developed without preliminary numerical simulations. The strategy was experimentally validated through tensile tests on polymeric FFF specimens with central holes of different sizes and shapes and compared with conventional slicer-generated infills. Relative to the best conventional baseline, the adaptive infill increased ultimate tensile strength by 12–20% and strain at maximum load by 19–35%, while elastic modulus changed only moderately (1–3%). Absorbed energy and specific strength were also enhanced. Digital Image Correlation showed a modified fracture mechanism, with delayed crack propagation from the hole due to the locally reinforced path arrangement. The results demonstrate that hole-aware, load-aligned path continuity can improve the mechanical performance of FFF components through a slicing-compatible workflow without increasing material usage or requiring simulation-driven planning.