## 3 Experimental Results and Analysis
### Spatial Distribution of Relative Cumulative Energy of BAD  
The energy of fragments in each scattering angle range was accumulated and normalized to obtain the relative accumulated energy distribution, as shown in Figure 15.  
Figure 14: Average energy distribution of EFP and target fragments in different scattering angle ranges. (**a**) \(L/D\) = 1.66 (**b**) \(L/D\) = 2.4 (**c**) \(L/D\) = 3.86. Figure 15 shows that the overall rate of increase in the BAD energy gradually decreased with the increasing scattering angle. The differences in the spatial distribution of the BAD energy between the three EFPs were mainly concentrated in the scattering angle range of 3-17\({}^{\circ}\), the distribution of other scattering angle ranges is basically the same. The total energy of the fragments within a scattering angle of 17\({}^{\circ}\) accounted for about 85% of the total energy of all fragments, indicating that the energy of the fragments with a large scattering angle was small. In the range of 3-17\({}^{\circ}\), the curve of the EFP with an \(L/D\) of 2.4 was the lowest, which reflects the shift of energy distribution towards the large scattering angle. In contrast, the fragment energy of the EFP with an \(L/D\) of 3.86 was concentrated in the small scattering angle region. The data in the scattering angle range of the same distribution were fitted in Figure 15, and the spatial distribution of the relative cumulative energy followed an exponential function. \[\frac{E(<\beta)}{E_{0}}=-90.97\exp(-\beta/9.81)+103.72 \tag{3}\]  
where \(E(<\beta)\) is the sum of the energy of the fragments with a scattering angle of less than \(\beta\), and \(E_{0}\) is the total energy of BAD. The energy of the residual EFP and the target plug fragments (i.e., the sum of the energy of the fragments with a scattering angle of 0\({}^{\circ}\)) accounted for 20-25% of the total energy of all fragments, thus indicating that a large part of the BAD energy was dispersed in scattering space around the projectile incident axis in a way that could threaten or even damage the internal components of an armored target. The relative cumulative energies of the EFP and target fragments were separated, as shown in Figure 16.  
Figure 16: Relative cumulative energy distribution of EFP and target fragments. (**a**) Target fragment:f (**b**) EFP fragment. Figure 15: Relative cumulative energy distribution of BAD. According to Figure 16, the difference in the BAD energy distribution between different EFPs was mainly expressed via the energy of the EFP fragments. When the \(L/D\) was 3.86, the energy of the EFP fragments was mainly distributed at 0-5\({}^{\circ}\), and the EFP fragment energy then increased slowly as the scattering angle increased. In comparison, the energy of the EFP fragments of the other two types of EFPs increased approximately linearly over the entire scattering range. These results suggest that a very large \(L/D\) will cause the energy of the EFP fragments to be concentrated closely to the projectile axis. Additionally, the cumulative energy of EFP fragments hardly increased when the scattering angle was greater than 20\({}^{\circ}\), indicating that the energy of EFP fragments was distributed in the range of 0-20\({}^{\circ}\). However, the energy distribution of the target fragments was not different beyond 25\({}^{\circ}\). Moreover, the energy distribution curves of the EFP with an \(L/D\) of 2.4 was the lowest from 7-13\({}^{\circ}\) for the EFP fragments and 7-16\({}^{\circ}\) for target fragments, thus indicating that the energy distribution of EFP fragments and target fragments in the corresponding range was concentrated at the large scattering angle and within the difference region of the energy distribution of all fragments, as shown in Figure 15.  
According to previously conducted analysis, the energy of EFP fragments was mainly concentrated in the scattering angle range of 0-20\({}^{\circ}\).