Anisotropic flexural behavior and energy absorption of 3D printed engineered cementitious composites (3DP-ECC) beams under low-velocity impact

This study systematically investigates the mechanical behavior and energy absorption properties of anisotropic 3D-printed engineered cementitious composite (3DP-ECC) beams under low-velocity impact, with a focus on performance variations across different loading directions. A comprehensive experimental program, including quasi-static compression, tensile, three-point flexural, and low-velocity impact tests, was conducted to evaluate the mechanical response and failure mechanisms of 3DP-ECC in the U, V, and W loading directions. The results demonstrate that 3DP-ECC exhibits significant anisotropy compared to Cast-ECC. Specifically, the W-direction exhibited a 33.4 % increase in flexural strength, along with enhanced energy absorption capacity, improved toughness, and reduced strain-rate sensitivity. Additionally, a novel methodology for calculating inertial forces and a predictive model for energy absorption were developed, categorizing impact energy into components associated with matrix fracture, fiber-matrix interactions, and inertial effects. The findings indicate that 3DP-ECC in the W-direction offers optimal impact resistance, while the U-direction exhibits the highest inertial force and acceleration, which may pose risks to structural integrity. This research offers valuable insights into the optimization and application of 3DP-ECC in impact-resistant infrastructure.