Functional Reprogramming of Intrinsic Pore Networks in Fused Filament Fabrication: Dual Transport Control of Resin Infusion and Load‐Mode‐Dependent Reinforcement

Inter‐bead pores in fused filament fabrication (FFF) are generally treated as defects to be eliminated. Here, these pores are coupled with additively manufactured inlets, primary channels, and outlets to construct a dual transport network (DTN) comprising a low‐resistance primary network for long‐range delivery and an intrinsic secondary pore network for local redistribution. Sealed poly(lactic acid) (PLA) preforms were used to determine how infill fraction and primary‐channel count affect vacuum‐assisted infusion and the post‐cure mechanical response. With seven primary channels, increasing the infill fraction from 20% to 40% reduced resin uptake from 19.92 to 10.91 g but prolonged the infusion time from 60.6 to 112.7 s, indicating that transport through the secondary pore network became rate controlling. At a fixed infill fraction of 20%, specimens containing 4, 7, and 10 primary channels exhibited infusion times of 17.8, 53.7, and 21.4 s, respectively, revealing hydraulic mismatch between primary delivery and secondary redistribution. Relative to uninfused specimens with the same channel architecture, resin infusion increased the tensile, flexural, and compressive strengths by 37.7%, 9.8%, and 290.3%, respectively. Tension and flexure combined higher stiffness and load capacity with lower energy absorption, whereas compression exhibited simultaneous gains in strength and energy absorption. These results demonstrate that intrinsic FFF pores can be reprogrammed from manufacturing defects into an internal network that supports both transport and load‐mode‐dependent reinforcement.