Architected Polymeric Reinforcement for 3D Printed Concrete: Topology Design and Failure Mechanism

While 3D printed concrete (3DPC) offers unprecedented geometric freedom, its formwork-free layer-by-layer extrusion induces inherent structural brittleness and weak anisotropic interfaces. To transition 3DPC into highly ductile composites, this study systematically investigates the flexural mechanics and topological design of continuous 3D printed polylactic acid (PLA) architected reinforcements. Various planar configurations—ranging from single-layer trusses and double-layer meshes to bio-inspired honeycombs—were fabricated at two diameter scales (2 mm and 4 mm) and evaluated through experimental testing and Concrete Damaged Plasticity (CDP) finite element simulations. Pull-out tests demonstrate that the intrinsic layer ridges of the FDM-printed PLA transform brittle debonding into a ductile interfacial "ploughing" mechanism without triggering macroscopic concrete splitting. In flexure, a diameter-driven failure paradigm is identified: slender 2-mm lattices succumb to progressive geometric instability, whereas robust 4-mm networks trigger a hybrid flexural-shear failure, unlocking extensive multi-stage cracking and dynamic "crack-and-bridge" interplay. Topologically, honeycomb architectures deliver unparalleled absolute performance, outperforming single-layer baselines by up to 765% in ultimate capacity. However, analysis of Specific Energy Absorption (SEA) unveils a critical lightweight efficiency paradox: despite lower absolute strengths, the 2-mm configurations achieve nearly double the SEA by fully exhausting their ductile deformation potential via plastic hinging. The validated FE models successfully capture the complex multi-peak oscillatory softening responses. These comprehensive findings provide foundational theoretical guidelines for the topological evaluation and deployment of mechanically robust, material-efficient architected reinforcements in next-generation automated construction.