# Design and Optimization of Origami-Inspired Orthopyramid-Like Core Panel for Load Damping
## 6 Result and Discussion
### Simulation Result and Comparison  
The ANSYS structural static solver was used to conduct the compression simulation of the orthopyramid-like core panels. The results revealed that the panels present large plastic deformation in compression, and the deformation presents a circular distribution on the tips. The distribution of stress on the element shows that the maximum stress occurs on the tip of the element. As illustrated in Figure 15, the simulation is accordant with the experimental results. The total deformation of the OL-4-3/4 model is illustrated in Figure 16a. The maximum total deformation is 4 mm at the bottom. The directional deformation of the OL-4-3/4 model is shown in Figure 16b. The maximum mechanical strain and the maximum equivalent stress of the designed panels during compression simulation are compared in Table 5. It is apparent that the similarity parameter affects the stress and the deflection on the simulated panels. It was found that the maximum \begin{table}
\begin{tabular}{c c c} \hline \hline
**Edge Number** & **Similarity Parameter** & **The Maximum Impact Forces (N)** \\ \hline \multirow{3}{*}{OL-3} & 1/2 & \(6851.8\pm 122.8\) \\  & 3/4 & \(5128.6\pm 442.0\) \\  & 5/6 & \(4699.6\pm 662.6\) \\ \hline \multirow{3}{*}{OL-4} & 1/2 & \(6911.0\pm 80.4\) \\  & 3/4 & \(3906.4\pm 339.4\) \\  & 5/6 & \(3448.2\pm 767.2\) \\ \hline \multirow{3}{*}{OL-6} & 1/2 & \(6620.8\pm 191.9\) \\  & 3/4 & \(3627.0\pm 104.4\) \\ \cline{1-1}  & 5/6 & \(2890.3\pm 166.2\) \\ \hline \hline \end{tabular}
\end{table} 
Table 4: The maximum impact forces produced by the panels. Figure 14: The experiment maximum impact forces. Figure 15: The compressive deformation of the OL-4-3/4 panel compared with the tested sample. equivalent stresses all decrease with the increase of w for 3-edged and 6-edged elements. For the 4-edged element, the minimum stress appears in a similarity parameter of 3/4. \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Edge Number**} & \multirow{2}{*}{**Similarity Parameter**} & \multicolumn{2}{c}{**Maximum Equivalent Strain**} & \multicolumn{1}{c}{**Maximum Equivalent Stress (MPa)**} \\ \hline  & 1/2 & 0.685 & 2330 \\ \cline{2-4}  & 3/4 & 0.550 & 1650 \\ \cline{2-4}  & 5/6 & 0.453 & 913 \\ \hline  & 1/2 & 446 & 1970 \\ \cline{2-4}  & 3/4 & 0.544 & 1100 \\ \cline{2-4}  & 5/6 & 0.676 & 1380 \\ \hline  & 1/2 & 0.602 & 2890 \\ \cline{2-4}  & 3/4 & 0.692 & 1490 \\ \cline{2-4}  & 5/6 & 0.422 & 1000 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Comparision of maximum mechanical strain and maximum equivalent stress. Figure 16: The compressive deformation of OL-4-3/4 panel. (**a**) The whole compressive deformation; (**b**) the \(z\)-directional compressive deformation. The impact property of the nine panels and their deformation were revealed using finite element simulations, too. Figure 17 illustrates the impact simulation of the OL-4-3/4 model. The ability of the structure to absorb energy and allocate force is explained by the collapse of the tips and stress concentration of the side edges. It indicates the effect of similarity parameter and the number of edges on the produced force. The table shows that the maximum produced force shows a decreasing tendency with the increase of edge numbers. Figure 18 shows the comparsion of the deflection degree of the tips in impact simulation. It is consistent with test results that the most deformed place of the orthopyramid-like element is the tip. The deformation value depends on the similarity parameter and the number of edges. The element with small similarity parameters exhibited high deformation on the tip and a small deformation distribution along the side edges. The elements with bigger similarity parameters exhibit lower deformation near the tips and the deformation spread along the side edges. Figure 19 shows the simulated results of the maximum plastic strain of the panels. It can be observed that there is no apparent relationship between the maximum plastic strain and the similarity parameter.