Numerical and experimental evaluation of maraging steel cellular topologies for ballistic panel design

• Innovative use of metallic cellular structures for ballistic panel against STANAG 4569 level 3 • Ballistic performance study of eight additively manufactured maraging steel cellular structures • Tabulated Johnson-Cook model for M300 steel was validated against ballistic tests • Three structures showed better ballistic performance compared to other targets • Three main mechanisms responsible for projectile core fracture were identified Although several papers dealt with the ballistic impacts of the panels with the cellular structures used as the filling, none of them were aimed at the investigation of such structures considering level II of STANAG 4569 standard. Therefore, this paper demonstrates the implementation of the metallic cellular structures with regular topologies into the ballistic panel as an effective solution against ballistic threats. First, the manufacturing process of specimens made from Maraging M300 steel with the basic characterization of the material properties is discussed. For this purpose, the Selective Laser Melting (SLM) technique with a maraging M300 steel (1.2709) powder is used to manufacture specimens, steel plates and selected cellular structure. In the second stage, the experimental tests of ball bearing and 7.62 × 39 AP BZ steel-core bullet impacts into the printed targets are conducted. Next, the Tabulated Johnson – Cook (TJC) constitutive model is correlated and validated, which is adopted to reproduce the behavior of M300 steel targets through numerical simulations replicating the conducted experimental tests. Satisfactory results are achieved proving the credibility of the numerical modelling strategy. Finally, eight selected 2D topologies are proposed and the numerical simulations of ballistic test according to STANAG 4569 level 2 are performed. For the cellular topologies three different failure mechanisms are identified, namely the plastic deformation and blunting of the core tip, axial fragmentation of the core and bending/shearing fracture of the core, influencing the ballistic effectiveness. Strong differences for different topological configurations could be observed. The results are promising in the scope of developing ballistic panels, and the paper provides a valuable guide for modelling and simulating the projectile impacts into the panels made of cellular structures.