Exploiting multiscale dynamic toughening in multicomponent alloy metamaterials for extreme impact mitigation

Abstract

<p>Mechanical metamaterials can unlock extreme properties by leveraging lightweight structural design principles and unique deformation mechanisms. However, research has predominantly focused on their quasi-static characteristics, leaving their behavior under extreme dynamic conditions, especially at length scales relevant to practical applications largely unexplored. Here, we present a strategy to achieve extreme impact mitigation at the macroscale by combining shell-based microarchitecture with an additively manufactured medium-entropy alloy (MEA) featuring low stacking fault energy (SFE). Notably, the shell-based architecture amplifies the effective dynamic stress within the metamaterial compared to truss-based morphologies, leading to the earlier activation of multiscale toughening mechanisms in the alloy. The low SFE of the MEA enables the evolution of a diverse array of defect types, thereby prolonging strain hardening behavior across seven orders of magnitude in strain rate. These fundamental insights could establish the groundwork for developing scalable, lightweight, impact-resistant metamaterials for structural and defense applications.</p>