Auxetic meta-concrete with customized materials and structures: Experiments and simulations

Abstract

In this study, the influence of material composition and structural geometry on the auxetic behavior of auxetic meta-concrete (AMC) under compressive loading was investigated. A novel integration using different ductility levels of ultra-high-performance fiber-reinforced concrete (UHPFRC) with tailored perforation designs is proposed to enhance the auxetic performance in the high-auxetic region. Three perforation geometries-diamond-(DP), elliptical-(EP), and peanut-shaped (PP) geometries-were designed and fabricated using UHPFRC mixtures with different fiber contents and ductility levels (ST00, ST13, and ST19). The results showed that the ductility and crack-bridging capacity of the constituent materials played a crucial role in enabling auxetic deformation. The use of strain-hardening UHPFRC (ST19) achieved the highest low-point stress (0.91 MPa) in the high-auxetic range by enhancing joint rotation and structural integrity. Among the different perforation geometries, DP-ST19 exhibited the greatest stiffness and strength, with peak stresses of 6.63 and 49.23 MPa and a specific stiffness of 297.57 J/g. By contrast, EP-ST19 and PP-ST19, with expanded joints, produced higher strain capacities (27.68 % and 36.09 %, respectively) and superior specific energy absorption (0.76 and 0.53 J/g, respectively) by promoting more uniform stress distribution and microcracking. These findings highlight the potential of using UHPFRC in AMC as a lightweight, energy-absorbing, and resilient material system, offering promising applications in blast-resistant and impact-mitigating infrastructure.