Advanced 3D-Printed auxetic structures: Mechanical performance evaluation of ECC in rotating rigid configurations

Abstract

This study investigated mechanical properties, including the negative Poisson's ratio (NPR) effect and energy absorption capacity, of single-cell unit rotation rigid body (SCRR) structures fabricated using 3D-printed engineering cementitious composites (ECC). Printable ECC mixtures were optimised for extrudability, buildability, and workability, achieving a compressive strength exceeding 40 MPa, tensile strain capacity above 4 %, and fracture toughness higher than $2\text{MPa}·m^{\frac{1}{2}}$. Models of cast SCRR structures and optimal printed paths were designed. Both the cast and printed SCRR specimens underwent uniaxial compression tests and were monitored using digital image correlation (DIC) technology. The compression curves from the experiments and ABAQUS simulations revealed three distinct deformation stages: elastic (Stage I), rotation (Stage II), and densification (Stage III). As the rotational angle (α) increased, Stage II expanded significantly, enhancing the energy absorption capacity. Specifically, the energy absorption (SEA) increased from 520.816 kJ/m³ at α = 30° to 880.314 kJ/m³ at α = 60°, whereas the compression force efficiency (CFE) was stable between 45° and 60°, demonstrating consistent performance. The anisotropy induced by printing in the specified direction facilitated fibre alignment at the SCRR joints, resulting in improved ductility and stress performance compared with cast specimens. Through this series of experiments, optimal SCRR design dimensions were proposed, confirming the potential of ECC-based SCRR structures to achieve auxetic behaviour. This study lays a foundation for the application of rigid rotational bodies in construction, offering insights into lightweight design and energy-absorption optimisation for building systems.