## 4 Results and Discussion
### Mechanical Tests
However, in the analysis of the synergistic effect, the phenomenon of the two structures is more complex. It is generally believed that the peak stress and energy absorption capacity of hybrid lattice structures can be greatly improved by filling ceramic built-in structures in metal lattice cells. However, in fact, in the unit cells discussed in this paper, the synergistic effect in terms of peak stress is only reflected in the ordinary hexagonal structure. For the ordinary single hexagonal honeycomb, the peak stress and energy absorption capacity of hybrid honeycomb structures can be greatly improved by filling the metal lattice cells with ceramic built-in structures. The peak stress and energy absorption capacity are due to the arithmetic superposition of separated metal shells and built-in ceramic structures. In terms of peak stress, the combination of the ordinary honeycomb and the built-in ceramic is increased by 1.58 times. This phenomenon is more obvious in the study of energy absorption in the ordinary honeycomb. When the ceramic and metal are combined, the peak load that the whole hybrid structure can bear is significantly greater than that of the single material, and the peak load that the hybrid structure is 1.8 times that of the single ceramic. The maximum strain that withstands is also increased significantly, and the deformation that can be withstood is 2.4 times of that of single ceramics. The energy absorption capacity of the hybrid structure is significantly greater than that of a single ceramic or metal and is also greater than the arithmetic sum of the two. The combination of the ordinary honeycomb and built-in ceramics has increased by 3.46 times. However, for the re-entrant hex auxetic structure, the synergistic effect of \(1+1>2\) is not found in term of peak load. For the concave structure, the compressive load of the re-entrant hexagonal single-phase ceramic (256.4 kN) is even higher than that of the metal-ceramic honeycomb hybrid structure (235 kN). In terms of energy absorption characteristics, the re-entrant hexagonal auxetic structure also shows obvious synergistic effects. After the combination of ceramic and metal, the peak load of the hybrid structure is slightly lower than that of single ceramic (the peak load that hybrid structure can bear is 0.92 times that \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Lattice Type** & **Mechanical Characteristics** & \begin{tabular}{c} **Inner** \\ **Ceramic** \\ \end{tabular} & \begin{tabular}{c} **Outer** \\ **Metal** \\ \end{tabular} & \begin{tabular}{c} **Hybrid** \\ **Structure** \\ \end{tabular} & \begin{tabular}{c} **Arithmetic Sum of** \\ **Inner and Outer** \\ \end{tabular} & **HAR** \\ \hline \multirow{3}{*}{Hex} & \
\begin{tabular}{c} peak load (KN) \\ \end{tabular} & 95.4 & 15.3 & 175 & 110.7 & 1.58 \\ \cline{2-6}  & strain (\%) & 2.3 & 5.6 & & \\ \cline{2-6}  & energy absorption (kJ) & 1.5 & 1.3 ([EMAIL_ADDRESS]\%) & 9.7 & 2.8 & 3.46 \\ \hline \multirow{3}{*}{Rehex} &
\begin{tabular}{c} peak load (KN) \\ \end{tabular} & 256.4 & 20.1 & 235 & 276.5 & 0.85 \\ \cline{2-6}  & strain (\%) & 2.9 & & 7.4 & & \\ \cline{1-1} \cline{2-6}  & energy absorption (kJ) & 4.8 & 2.4 ([EMAIL_ADDRESS]\%) & 21.6 & 7.2 & 3 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Synergistic effect analysis of quasi static compression test. Figure 5: Synergistic effect analysis of quasi static compression test (**a**) conventional hex structure, (**b**) re-entrant hex auxetic structure; Synergistic effect of hybrid honeycombs under dynamic Hopkinson compression bar experiments at strain rate of 2.54 \(\times\) 103/s (**c**) conventional hex structure, (**d**) re-entrant hex auxetic structure. of pure ceramic). There is an obvious increase in the highest strain for the hybrid structure (the deformation it can bear is 2.4 times of that of pure ceramics). The combination of the re-entrant honeycomb and built-in ceramics has increased by 3.00 times.