PSI - Issue 35

Deniz ÇelikbaŞ et al. / Procedia Structural Integrity 35 (2022) 269 – 278 D. C¸ elikbas¸ / Structural Integrity Procedia 00 (2021) 000–000

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based armors can maintain protectiveness with thinner and lighter plates. Ceramic plates dissipate the projectile’s kinetic energy by fracturing, while metal plates dissipate energy by plastic deformation. Also, the ceramic plate’s high hardness values erode or shatter the projectile and reduce blunt-body trauma Ruys (2019). Along with these features, ceramic plates are very popular in the defense industry. The most accessible ceramic material in the armor industry is alumina. From the origin of the ceramic-based armors, alumina dominates the industry because of its low cost, better achievability, high hardness values, and lightweight Ruys (2019). Therefore, many researchers focused on alumina. For example, Toussaint and Polyzois conducted experiments on alumina tile and compared di ff erent material models to find the best-suited model com pared to their experimental results Toussaint and Polysois (2019). Tepeduzu and Karakuzu investigated three di ff er ent thicknesses of alumina with various backing materials such as aramid, epoxy, S2 glass, carbon-aramid, and hybrid aramid. They examined di ff erent combinations of backing materials with varying ratios of thickness. They found the protectiveness was increased when alumina ceramic tile is backed with aramid / epoxy layers Tepeduzu and Karakuzu (2019). Scazzosi et al. conducted high-velocity experiments on alumina and used these experiments to caliber their numerical model Scazzosi (2020) . Xiao et al. performed simulations of the projectile impacting alumina plate to determine the residual velocity and mass of the projectile and plate Xiao (2020). On-body armor ceramic plates are used to block the projectile. High hardness values of ceramic plates shatters and erodes the impactor, and various other parameters a ff ect the plates’ performance. For example, the armor may contain a mosaic structure to be protective for more than one hit, or they may have di ff erent surface profiles to change the direction of the projectile Ruys (2019). The change in the direction of the projectile causes a loss of penetration energy. The e ff ect of surface profiling is rather an unstudied area because of the production di ffi culties. However, the developments of three-dimensional printing procedures such as binder jetting Mariana (2021) or selective laser sintering Chen (2018) can produce such structures. Even though experimental results are needed to explore the theory, simulations can be used as an initial step. In this paper, the e ff ects of surface profiling are investigated by numerical analyses. To explore the performance of surface profiling, the specific kinetic energy absorption (SKEA, kinetic energy absorption per unit mass) values of the tiles are compared. The remainder of the paper is organized as follows: In the next section, a finite element (FE) simulation model is established first to represent a steel projectile impacting a ceramic plate. The results are compared with the experimental results of Toussaint and Polysois (2019). Then, the validated FE model is used to explore the e ff ect of surface profiling on the SKEA values of the ceramic tiles. The paper culminates with the conclusions drawn from this study.

2. Numerical Models

Numerical models provide an understanding of the phenomena; however, numerical models needs a validation process. In this study, LS-DYNA software is used. A numerical model generated to explore ballistic impact. Firstly, the numerical model validated by the experimental results of Toussaint and Polysois (2019). Then the validated numerical model is used to investigate the e ff ect of surface profiling.

2.1. Element Formulation

Toussaint and Polyzois experimented with alumina and compared their experimental results with di ff erent numer ical models to suggest the best way to model a steel projectile impacting an alumina plate. They tried three di ff erent material models to simulate brittle materials. While two of these material models used smoothed particle hydrody namics (SPH) element formulation, one model used constant stress solid element formulation. Between these material models and element formulations, Johnson-Holmquist 2 (JH2) with SPH element formulation leads to the closest results to the experimental results Toussaint and Polysois (2019). Similarly, Scazzosi et al. compared SPH element formulation with FE formulation to represent the phenomenon. To model impact by FE formulation, an nonphysical el ement erosion criterion must be used. On the other hand, SPH is a mesh-free method and can handle severe distortions Scazzosi (2020). Therefore, they suggested using SPH element formulation with the JH2 material model. Similarly, Johnson et al. found that SPH can handle the debris and fractures without adding any erosion criteria Johnson (1996).