## 3 Results and Discussion
### Numerical Validation
#### 3.1.2 Validation of Sandwich Panels  
The experiments conducted by [PERSON] et al. [6] only involved a single plate, whereas this study focuses on the blast response of a sandwich panel. Therefore, it is essential to validate the numerical model of the sandwich panel. Experimental data provided by [PERSON] et al. [14] are relevant as they also investigated the blast response of a sandwich panel, despite using a nonavicetic core geometry. The experimental setup, objectives, and material properties align closely with those used in this paper. [PERSON] et al. [14] conducted experiments on metallic trapezoidal corrugated-core sandwich panels under air-blast loads. Figure 7 shows the experimental setup and configuration of a trapezoidal corrugated-core sandwich panel. Their study primarily explored the influence of geometric parameters and SoD on midpoint displacements. The horizontal plane had dimensions of 452 mm \(\times\) 440 mm, and the exposed area of the blast or the corrugated-core dimensions were 300 mm \(\times\) 288 mm.  
The numerical model utilized a symmetric-quarter model with symmetric boundaries fixed at the outer sides. The material properties of 304 stainless steel were represented using a modified J-C model, with parameters listed in Table 2. A 55 g cylindrical TNT charge, with a radius of 17.5 mm and height of 37.2 mm, was  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \multirow{2}{*}{**SoD**} & \multirow{2}{*}{**Exp.**} & \multicolumn{2}{c}{**CONWEP**} & \multicolumn{2}{c}{**SPH**} & \multicolumn{2}{c}{**MMALE**} \\ \cline{3-8}  & & **Sim.** & **Err.** & **Sim.** & **Err.** & **Sim.** & **Err.** & **Sim.** & **Err.** \\
**(mm)** & **(mm)** & **(mm)** & **(\%)** & **(mm)** & **(\%)** & **(mm)** & **(mm)** & **(\%)** \\ \hline
150 & 17 & 17.81 & 4.76 & 17.75 & 4.41 & 17.41 & 2.41 \\
200 & 12.7 & 14.77 & 16.30 & 14.23 & 12.05 & 12.54 & \(-\)1.26 \\
250 & 11.3 & 11.23 & \(-\)0.62 & 11.42 & 1.06 & 10.27 & \(-\)9.12 \\ \hline \end{tabular}
\end{table}
Table 4: Permanent displacement from various air-blast models and experimental results [6].  
Figure 6: Comparison of permanent displacement (\(\delta_{p}\)) from various air-blast models with experimental results [6].  
Figure 7: **(a)** Experimental setup for the blast test of trapezoidal corrugated-core sandwich panels. **(b)** Configuration of the trapezoidal corrugated-core sandwich panel [14].  
method due to its specific shape, while the CONWEP method approximated the charge as a spherical air blast.  
Figure 8 shows a correlation plot of \(\delta_{p}\), comparing experimental and numerical simulation results. The close alignment of data points around the line of a perfect match indicates strong agreement between numerical predictions and experimental data. The average error across all samples, as detailed in Table 5, is less than 10%. To further validate the numerical model's reliability, deformation modes of three sandwich panels with different core configurations were compared between numerical simulations and experimental results. As shown in Figure 9 (left), the numerical model accurately reproduces major deformations, including local indentation in the middle area of the corrugated core and plastic buckling of the core web. Figure 9 (right) also shows the cross-sectional displacement profiles, showing close correspondence between numerical and experimental results. Overall, the numerical methods employed in this study demonstrate validity and accuracy suitable for subsequent optimization processes.