Enhancing the fracture and flexural behavior of 3D printed strain-hardening cementitious composites with nature-inspired single and double Bouligand structures

Strain-hardening cementitious composites (SHCC) have gained increasing attention in 3D concrete printing. However, their implementation in structural applications remains limited. Inspired by the mantis shrimp and coelacanths, 3D printed SHCC with single and double Bouligand structures are fabricated. To evaluate their fracture and flexural performance, three-point and four-point bending tests on notched beams and four-point bending tests are conducted. Results show that the double Bouligand-printed specimens with a pitch angle of 15° exhibit the highest fracture toughness, which is 18.04 times, 2.63 times, and 1.86 times greater than that of parallel-printed, cross-printed, and mold-cast specimens, respectively. Meanwhile, single Bouligand-printed specimens with a pitch angle of 30° exhibit the highest flexural strength and flexural toughness. The enhanced toughness and energy dissipation in Bouligand-printed SHCC are attributed to the combined effects of crack twisting and bridging, which reflects the toughening mechanisms found in biological systems.