## 3 Results and Discussion
### Application of the Optimized Auxetic Sandwich Panel for Armored Fighting Vehicle Protection
#### 3.4.2 Simulation Results  
Figure 21 shows the simulation results of the AFV subsystem deformation under an 8 kg TNT blast. All deformation and failure modes that occur in the OSP and SSP are consistent with the failure modes summarized in the research by [PERSON] et al. [69]. As seen in Figure 21a, the 10 mm OSP without a protective structure fails to meet structural integrity requirements due to severe perforation. According to the Cockcroft-Latham damage failure criterion, petaling damage occurs in the middle of the OSP, allowing blast fragments and debris to enter the occupant compartment. Conversely, other configurations, including the 20 mm OSP without a protective structure, maintain structural integrity. As seen in Figure 21b-d, no perforations occur in the OSP. Failure mode I, i.e., large inelastic deformation, occurs in the OSP for the AFV subsystem with 20 mm OSP and protective structure. However, the 20 mm OSP without a protective structure suffers very large deformation compared with the AFV subsystem with the protective structures. From Figure 21c, the SSP of the AFV subsystem with optimized AFSP experiences failure mode IIc, i.e., completely tearing at the center area and forming a ring shape or capping. A different failure mode is observed in the SSP of the AFV subsystem with optimized ASP DAH, where the SPP experiences failure mode IIc, i.e., partial tearing in the central area of the blast, as seen in Figure 21d. Figure 22 shows the dynamic responses of the AFV subsystem both with and without protective structures, focusing on the midpoint displacement and acceleration of the OSP. The results demonstrate that applying protective structures to AFVs significantly reduces the  
Figure 21: Failure modes of the occupant and struck sides (**top**) and deformation process from 0 to 10 ms (**bottom**) of the AFV subsystem for different types of structures: (**a**) 10 mm occupant side plate (OSP) without a protective structure, (**b**) 20 mm OSP without a protective structure, (**c**) with optimized AFSP, (**d**) with optimized ASP DAH. displacement and acceleration of the floor or OSP. Furthermore, the optimized ASP DAH structure decreases OSP deformation more effectively than the 20 mm single plate and the optimized AFSP. The optimized ASP DAH structure achieves a maximum displacement reduction of 56.99% and 39.00% compared to the 20 mm single plate and optimized AFSP, respectively. Additionally, it reduces the maximum acceleration by 52.55% and 43.56% relative to the single plate and optimized AFSP, respectively, indicating its superior performance. Figure 23 presents the energy absorption (EA) and SEA of the AFV subsystem with various structural types. It can be seen that in the AFVs with protective structures, the core structure absorbs the most energy, followed by the SSP and OSP. Additionally, the energy absorbed by the optimized ASP DAH exceeds that of both the 20 mm single plate and the optimized AFSP. Notably, the optimized ASP DAH structure achieves SEA improvements of 335.00% and 48.30% compared to the 20 mm single plate and the optimized AFSP, respectively. This highlights the superior effectiveness of auxetic structures in absorbing energy under localized loads compared to other structures. Table 9 summarizes the blastworthiness parameters of AFV subsystems with and without protective structures. Overall, the ASP, particularly ASP DAH, demonstrates significant potential for application as a protective structure in AFVs. Compared to conventional structures such as honeycomb and aluminum foam, auxetic structures exhibit superior performance, a finding consistent with other studies [32; 33; 37]. The enhanced performance is attributed to the unique deformation mechanism of auxetics, specifically their NPR, which causes the structure to density in regions near the blast source. This densification increases the energy absorption capacity and enhances the blast resistance of the structure.