## 4 Results and Discussion  
### Mechanical Tests  
Figure 3a shows the displacement-load curves of the two hybrid honeycomb samples during the compression process. It can be seen that the load curve of the conventional hex hybrid structure is lower than that of re-entrant hybrid lattice. When the compression displacement of the conventional hexagonal hybrid structure reaches 2.59 mm, the compression load drops drastically from peak 175 kN, and the ceramics materials are damaged and crushed into powder. The pressure value of the re-entrant hybrid lattice also increases with the increase in compression displacement. When the compression displacement is 2.75 mm, the compression load reaches a peak value of 235 kN. However, no sudden drop is observed after the peak value, which is quite different from that of the conventional hex hybrid structure. The compression load decreases slowly because only the upper surface of the re-entrant hybrid lattice is damaged, demonstrating superior compression resistance of the global composite structure. The compression load of the re-entrant hybrid lattice remains at 200 kN, at the compression displacement of 3.33 mm, so the re-entrant hybrid lattice can withstand a higher compression load than the conventional hex hybrid structure, and the re-entrant hybrid honeycomb can also resist a larger compressive displacement. During the compression process of re-entrant hybrid lattice filled with ceramics, the load decreases slowly with the increase of compression displacement, and the infilled ceramics fail accordingly. The conventional hexagonal hybrid structure failed at the compression displacement of 2.59 mm, exhibiting sudden burst failure features, and the compression load decreased instantaneously, as shown in Figure 3b. It shows that stress concentration within the conventional hexagonal hybrid structure will trigger ceramic crushing and bursting and induce global composite structure failure. Through comparison between these two types of hybrid honeycomb structures, it can be seen that the re-entrant hybrid lattice cannot be damaged instantaneously and shows good compression resistance--because concave shrinkage deformation on both sides can produce remarkable constraint, thus increasing the hydrostatic pressure within ceramic materials. It can be seen from Figure 3c that cracks are formed in the upper half of the built-in ceramic within the re-entrant hybrid lattice, while the lower half is intact, and the overall structure exhibits remarkable structural integrity. Strain field within the built-in ceramic matrix surrounded by a metal structure frame at different displacement steps is detected and recorded with DIC equipment, as illustrated in Figure 4a-f. It can be seen from Figure 4a that when the compression strain of the conventional hex structure along the vertical direction is 0.5%, the strain value is low and evenly distributed within ceramic matrix. The maximum strain of built-in ceramic along the horizontal direction is 0.62%, and the strain of the most built-in ceramic in the horizontal direction is less than 0.06%. When the compress strain along the vertical direction is 2.88%, \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline
**Fe** & **Cr** & **Ni** & **Mo** & **Mn** & **Si** & **P** & **C** & **S** \\ \hline Balance & 16–18 & 10–14 & 2–3 & \(\leq\)2 & \(\leq\)1 & \(\leq\)0.045 & \(\leq\)0.03 & \(\leq\)0.03 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Chemical composition of the 316L stainless steel. there is an obvious vertical area with a large horizontal strain within a regular hexagon, as shown in Figure 4b. Afterwards, there is an obvious vertical region with a large horizontal strain. The horizontal strain of most ceramics in this region is greater than 1.80%, and the maximum horizontal strain is 3.10%. Finally, as shown in Figure 4c, when the compression failure strain along the vertical direction is 5.75%, the global horizontal strain of the most ceramic matrix is greater than 5.22%.