This project investigates dynamic fragmentation in metals, traditionally analyzed within a statistical framework that attributes limited energy absorption in protective structures to material and geometric flaws. Here, we propose an alternative approach, integrating a deterministic component into fragmentation mechanisms. To validate this new theory, we have devised a comprehensive experimental, analytical, and numerical methodology to address several canonical fragmentation problems, each defined by distinct geometric and loading conditions that make them readily identifiable from a mechanical standpoint. The research examines 3D-printed specimens of four engineering metals, designed with controlled porous microstructures and commonly utilized in aerospace and civilian security applications. The objective is to determine whether, at sufficiently high strain rates, fragmentation mechanisms transition from being defect-controlled to inertia-controlled. Validating this new statistical-deterministic framework has revealed that defects play a reduced role in high-rate fragmentation, which would lower the entry barriers for 3D-printed materials in energy-absorbing applications. This shift has the potential to reduce production, transportation, repair, and energy costs of protective structures without compromising their energy absorption capabilities. Preliminary outcomes of the project have demonstrated through a tripartite approach —experiments, computational models, and analytical formulations— that multiscale inertia in porous materials serves as a robust regularization mechanism which delays plastic localization and fracture. At high strain rates, inertia diminishes the influence of defects in the dynamic fracture of ductile porous materials.
