## 3 Results and Discussions
### Dynamic Load Case  
For the dynamic load case, a ball with a diameter of 120 mm and a mass of 9 kg impacts the battery pack at a speed of 3.3 m/s. This specific ball was selected to match an experimental setup available for potential real-world testing, ensuring the simulation is as close to practical conditions as possible. Since the cell material lacks a defined strain rate, this scenario represents the worst-case situation, likely resulting in the highest deformation of the cells. The dynamic load case for impact has the same kinetic energy dislocated by the ball in all the load cases, and the primary parameter used to evaluate the results is the \(z\)-axis intrusion into the pack, which measures the extent of penetration and deformation caused by the impact. The intrusion is the most relevant parameter that can affect the thermal runaway in a pack of batteries during a crash [31]. In the V1 configuration, as depicted in Figure 15, the maximum Z intrusion without any spacers is 14.2 mm. When aluminum spacers are used, the intrusion is significantly reduced to 8.2 mm, a value also observed with standard PLA spacers. However, when PLA is subjected to a temperature of 60 \({}^{\circ}\)C, the intrusion increases slightly to 8.8 mm, indicating a modest loss in performance. In the V2 configuration, illustrated in Figure 16, the maximum Z intrusion reaches 9.8 mm without the use of spacers. With the introduction of aluminum spacers, the intrusion is notably decreased to 7.5 mm, and a reduction to 8 mm is seen with standard PLA spacers. However, when PLA is exposed to a temperature of 60 \({}^{\circ}\)C, the intrusion slightly rises to 8.3 mm. It is worth mentioning that the overall deformation on the first row of cells is also reduced. In the V3 configuration, as shown in Figure 17, the maximum Z intrusion without spacers is measured at 10.1 mm. The addition of aluminum spacers significantly lowers this intrusion to 7.3 mm, a reduction similarly achieved with standard PLA spacers, 7.6 mm. However, when the PLA is heated to 60 \({}^{\circ}\)C, the intrusion slightly increases to 7.8 mm, indicating a minor decline in effectiveness. The overall deformation of the first row of cells has improved. Figure 14: Compression cylinder, cell configuration V3, center-cut deformation for different spacer materials: (**a**) aluminum; (**b**) printed PLA; (**c**) printed PLA at 60 \({}^{\circ}\)C.  
Figure 16: Dynamic loading intrusion in V2 cell configuration: (**a**) no spacers; (**b**) aluminum; (**c**) printed PLA; (**d**) printed PLA at 60 \({}^{\circ}\)C.  
Figure 15: Dynamic loading intrusion in V1 cell configuration: (**a**) no spacers; (**b**) aluminum; (**c**) printed PLA; (**d**) printed PLA at 60 \({}^{\circ}\)C.  
Stresses were also evaluated, shown in Figures 18-20, to better understand the phenomenon of increased stiffness. The scale, in GPa, was chosen in regards to the literature for the deformation of 18650 cells [32]. It was observed that the stresses when using spacers in the lower rows are lower. The contact stress between batteries is also reduced. A significant portion of the load is absorbed by the spacers, which, even if they deteriorate, protect the batteries. The spacers play a crucial role in dissipating stress concentrations, with this effect being most evident in V1, Figure 18, where some of the forces are also absorbed by the lateral cells, which would otherwise remain unaffected. In this case, the presence of spacers demonstrates its utility. Figure 17: Dynamic loading intrusion in V3 cell configuration: (**a**) no spacers; (**b**) aluminum; (**c**) printed PLA; (**d**) printed PLA at 60 \({}^{\circ}\)C.  
Figure 18: _Cont._  
Previous studies have explored various approaches to improving the intrusion resistance and deformation behavior of battery packs. In [33], a multifunctional battery system for energy dissipation was proposed by sacrificing some cell space in favor of cylindrical deformable spacers.