Effects on strut diameter of 3D-printed lattice for cementitious composites on flexural performance: A case study based on digital image correlation (DIC) and acoustic emission (AE) techniques

The utilization of additive manufacturing (AM) brings new opportunities and challenges in ocean engineering. This study investigates the flexural behavior and damage evolution of cementitious beams reinforced with 3D-printed body-centered cubic (BCC) lattices, with emphasis on the roles of strut diameter. Two lattice groups, which share the same cell size and orientation, were fabricated from polylactic acid (PLA) and embedded inner cement with three strut diameters (2.0, 2.5, and 3.0 mm). Three-point bending tests were conducted accompanied with morphology observation for failure pattern analysis, digital image correlation (DIC) for full-field strain mapping and acoustic emission (AE) monitoring for ring-down counts and accumulated energy. Results indicate that increasing strut diameter significantly enhances the mechanical performance in stiffness, ductility and crack bridging. Specimens with thicker struts (3.0 mm) exhibited a prolonged post-peak response, more uniform stress distribution and a transition in failure mode from PLA tearing to multi-crack evolution. With equal strut diameter, the BCC group with one additional straight strut per cell showed a denser network of finer cracks due to its higher nodal connectivity and interfacial area. The findings demonstrate that strut diameter and lattice topology are crucial for optimizing the toughness and damage tolerance of lattice-reinforced marine cementitious composites.