Low-Velocity Impact Behavior of Auxetic Cementitious Cellular Composites (ACCCs)

Abstract

Auxetic cementitious cellular composites (ACCCs) exhibit promising mechanical properties under static loading conditions, including high fracture resistance and effective energy dissipation. However, their performance under impact loading remains largely unexplored. In this study, two ACCCs—designated P25 and P50—featuring different aspect ratios were designed using additive manufacturing (AM)-assisted casting and evaluated under low-velocity impacts using a Schmidt hammer with consistent impact energy. Impact resistance was assessed based on energy absorption, localized damage, crack propagation, and peak reaction force. In addition to single-impact testing, multiple impacts were applied until specimen failure, with performance compared against a reference specimen incorporating circular holes. Strain distribution during impact was captured using Digital Image Correlation (DIC) with a high-speed camera. A numerical model accounting for strain rate effects was developed to simulate the impact behavior of the ACCCs. The results reveal that the ACCCs significantly outperformed the reference design in terms of impact resistance, showing reduced localized damage, increased contact stiffness, and enhanced energy absorption under multiple impacts. This improved performance is attributed to the auxetic behavior, which pulls more material into the impact zone, enhancing energy dispersion and minimizing localized damage, thereby preserving the overall structural integrity. Among the two designs, P50 demonstrated superior impact resistance due to its enhanced auxetic behavior, which engages more ligaments in energy dissipation and further reduces localized damage. Given the widespread availability of cementitious materials, this study highlights the potential of ACCCs as lightweight, high-performance protective structural materials for impact mitigation in infrastructure applications.