PSI - Issue 60

Prince Jeya Lal Lazar et al. / Procedia Structural Integrity 60 (2024) 185–194 Author name / StructuralIntegrity Procedia 00 (2019) 000–000

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the order of 0.76 mm, 1 mm, and 1.5 mm. The cell wall spacing was set to 30.5 mm for all the load cases. Considering the panel’s symmetry and loading symmetry, a quarter model of the panel was modeled to minimize the computational cost. All the edges of the two outer faces of the panel were applied with fixed boundary conditions whereas, the edges of the two inner faces were applied with symmetry boundary conditions as presented in Fig 3. A series of simulations were performed for various load cases by varying the charge mass, standoff distance, and core thickness as presented in Table 1. Table 1. Load cases for surface and underwater explosions Variable Level Mass of TNT (kg) 1 2 3 Core Thickness (mm) 0.76 1 1.5 Standoff Distance (mm) 100 125 150

Fig. 3 Typical boundary conditions applied to sandwich panels for surface and underwater explosion [2] The sandwich panels were made of super-austenitic AL6XN steel, an elastic-plastic material for numerical analysis. Hence, the Johnson-Cook (J-C) constitutive model equation [19] incorporating material plasticity, temperature, and strain rate effects was utilized in these simulations. The mechanical and strength properties of AL6XN steel are presented in Table 2. & = ( + 68 7 )(1 + ̇ 6∗ 7 ) C1−D :(: # : $ (: # E 5 F (5) Table 2 Material properties for AL6XN steel [19] E A B C n m ̇ Tt Tm Cp kg/m 3 GPa MPa MPa s -1 K K J/kg-K 7850 161 0.35 400 1500 0.045 0.4 1.2 0.001 293 1800 452 The sandwich panel face sheets were meshed with C3D8R solid elements and the core was meshed with S4R shell elements. It was ensured that the meshed elements were with aspect ratio one. By using tie constraints, the face sheets were fixed to the core. From the mesh sensitivity analysis, it was concluded to use a mesh size of 1.5 mm. The current simulation was validated with the experimental results and numerical results from the literature [19] and is presented in Table 3 and Fig 4.