## 3 Results
### Comparison of Energy Absorption and Floor Deformation  
Figure 8 presents a comparison of the deformation characteristics of the EAFs obtained from the head impact simulations. Each EAF model is illustrated in three different states: the initial, at 2 ms, and at the maximum deformation, respectively. Regarding the Igelkott Floor (Figure 8a), the deformation mechanism of the floor under the head impact area can be characterized as a typical buckling with a fixed-fixed end condition since the spikes at the ends are securely connected to the upper and lower layers. The presence of an array of thin spikes prevents the bottoming-out phenomenon. Conversely, in Kradal (Figure 8b), a distinct bottoming-out phenomenon can be observed. When terminated to large compressive strains, the foam cells inside the floor collapse, causing the opposing cell walls to crush together [55], resulting in contact between the top and bottom hard exterior surfaces. In the case of SmartCells (Figure 8c), the thick hollow rubber cylinder undergoes lateral collapse without experiencing bottoming out. This can be attributed to the presence of connecting rubber on the top half, positioned between each column. The connecting rubber not only restricts the deformation but also causes the buckling to primarily occur in the bottom half of the column. Additionally, the thinnest OmniSports (Figure 8d) does not show a significant bottoming-out phenomenon, which can be attributed to its higher Young's modulus at low strains compared to the Kradal. Figure 9 illustrates a visual representation of energy distribution in the accident reconstruction simulations, including the head kinetic energy, EAF internal energy, and EAF sliding energy. Head kinetic energy exhibits a similar trend to their corresponding linear velocities generally, and is attenuated to an approximate minimum value against different EAFs during impact. EAF internal energy indicates that SmartCells exhibits the \begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & **HIC** & \begin{tabular}{c} **Peak Angular** \\ **Velocity [rad/s]** \\ \end{tabular} & \begin{tabular}{c} **Peak von Mises** \\ **Stress [MPa]** \\ \end{tabular} & \begin{tabular}{c} **Peak 1 st** \\ **Principal Strain** \\ \end{tabular} & \
\begin{tabular}{c} **Risk of Skull** \\ **Fracture * \\ \end{tabular} &
\begin{tabular}{c} **Risk of** \\ **Concession ** \\ \end{tabular} \\ \hline Igelkott & 2400 & 18 & 47 & 0.171 & 0.947 & 0.375 \\ Kradal & 3493 & 23 & 70 & 0.216 & 0.984 & 0.703 \\ SmartCell & 1304 & 24 & 27 & 0.225 & 0.456 & 0.765 \\ OmniSports & 4356 & 20 & 72 & 0.209 & 0.991 & 0.652 \\ Concrete & 10,507 & 25 & 80 & 0.253 & 0.999 & 0.901 \\ \hline \hline \end{tabular}  
* Based on the risk curve function from [PERSON] et al. (2007) [50]. ** Based on the risk curve function from [PERSON] et al. (2022) [49].  
\end{table} 
Table 3: Simulation results of the fall accident cased against different EAFs. Figure 7: (**a**) Comparison of peak von Mises stresses (MPa) on the cortical bone against four EAFs and concrete ground of Case 3. (**b**) Accident reconstruction of head impact initial posture on forward falling. (**c**) Comparison of the peak 1 st principal strain on the brain tissue of Case 3. (**d**) the medical image of Case 3, which is from the research [52]. Copyright (CC BY-NC-ND 3.0 IE). highest peak energy absorption, resulting in a minimal G-max during head impact. It is followed by Igelkott Floor, while Kradal and OmniSports have the lowest peak value. However, Igelkott Floor demonstrates the greatest energy absorption after impact, while SmartCells exhibits the smallest. By considering the head's kinematics, it is revealed that less energy from the Igelkott Floor is ultimately transferred to the head in this impact scenario, as evidenced by the lowest linear and angular velocities of the head after impact (as shown in Figure 6).