## 3 Results and Discussions
### Energy Absorption Capabilities  
The energy absorption behavior of a structure refers to its ability to dissipate energy without experiencing any failure, especially during impact or deformation. Energy is usually converted into other forms, such as plastic deformation, without causing the material or structure to fracture or shatter. The lattices deform significantly due to their high porosity. To evaluate the energy absorption capacity of lattice structures, it is necessary  
Figure 12: Stress–strain curves (**a**) uniform specimens, (**b**) horizontal graded specimens, (**c**) vertical graded and (**d**) radial graded. to define the relevant parameters. Energy absorption per unit volume (\(W\)) is the most commonly used way to represent the energy absorption capacity (Equation (7)) [17]:  
\[W=\int_{0}^{\epsilon_{d}}\sigma(\epsilon)d\epsilon \tag{7}\]  
where \(\epsilon_{d}\) is the maximum strain and \(\sigma\) and \(\epsilon\) represent the compressive stress and strain, respectively. The value of energy absorption per unit volume is the area enclosed by the stress-strain curve and the strain axis. Specific Energy Absorption (\(SEA\)) is defined as the sum of energy absorbed per unit mass [62]. It is calculated as total energy absorption (\(W\)) divided by mass (\(m\)) (Equation (8):  
\[SEA=\frac{W}{m} \tag{8}\]  
Table 4 shows the total energy absorption (\(W\)) and \(SEA\) values of the lattice structures. The total energy absorption of RG configurations is high in all lattice structures except the chiral structure. For the RG configurations of FGLSs, an energy absorption of 5.505 KJ was found in the re-entrant specimen and 8.907 KJ in the rotation specimen. This indicates that the internal microstructure design of the RG configuration can absorb energy more effectively. As shown in Figure 13a, the best total energy absorption results in all combinations were obtained in the chiral structure. In the chiral structure, the uniform lattice has the highest energy absorption. It was followed by the horizontal graded structure with only 7% lower energy absorption. Among all of the structures, the highest energy absorption was obtained in chiral structures. Although the uniform chiral lattice has the highest energy absorption, FGLSs generally performed well in terms of energy absorption. The best SEA performance was also obtained with chiral structures (Figure 13b). These results indicate that chiral designs would give good results in applications where high toughness and energy absorption would be expected. The fact that RG structures have better energy absorption capabilities than uniform structures in rotation and re-entrant structures shows the energy absorption potential of FGLSs. These results can be further improved by making modifications to the unit cell designs. Re-entrant lattice structures, which have weaker compressive strength values than other structures, show a better energy absorption performance. This indicates that such designs have a high energy absorption potential. Although the re-entrant structure had a weak first compressive stress value, its high energy absorption performance indicates that the energy absorption capacity of this design is more critical than the compressive strength. The results obtained for lattice with different configurations designed within the scope of this study show that the internal design (cell model) of the structures is decisive in obtaining a more ideal energy-absorbing structure in line with the literature [63]. The  
Figure 13: (**a**) Total energy absorption and (**b**) specific energy absorption results of uniform and FGLSs. maximum energy absorption capacity value (19.381 KJ) and the maximum _SEA_ value (3649.905 KJ/kg) were obtained in the uniform configuration of the chiral lattice structure. This was due to the high strain value of the uniform configuration of the chiral structure, as well as the high compressive stress peak values in the plateau region.