## 3 Results and Discussion
### Influence of Projectile Material
#### 3.1.2 Impact Process  
High-speed cameras were used to record the impact by various types of projectiles on a braided composite target. Figure 7 shows the impact of a gelatin projectile in the Gelatin-2 test. As the impact velocity is extremely high in the tests using gelatin projectile, the gelatin projectile deformed and failed to maintain its original cylindrical geometry. The deformation phenomenon of gelatin projectile was investigated in our recent study [51] and corresponding internally supported gelatin bird projectile were used to improve this undesirable deformation. It is found that the deformed gelatin projectile mainly affects the load characteristic. Considering the flow characteristic of gelatin projectile during impact, the deformation of the gelatin projectile before impact has limited influence on the damage features of the composite target. Therefore, the gelatin projectile could be comparable with other projectile.  
The cylindrical gelatin projectile first contacts the target at 1.32 ms and undergoes a significant flow during the impact, which is fully consistent with reports in the literature. The triaxial braided composite target undergoes a large bending deformation under the impact of the gelatin projectile, which absorbs the impact energy to a large extent. Finally, the composite target plate is not perforated by the gelatin projectile, and the target plate recovers completely from the bending deformation. The large bending deformation of the target during impact results in delamination and matrix cracking of the target. Since the  
Figure 6: Energy absorption of 2D triaxial braided composites impacted by various projectiles.  
Figure 7: High-speed photographs of impact on 2D triaxial braided composite target plate of gelatin projectile at an impact velocity of 213 m/s.  
gelatin projectile is less hard than the carbon-fiber composite target, the target suffers no significant fiber breakage.  
Figure 8 shows the impact of the titanium-alloy projectile perforating a 2D triaxial braided composite target in the Ti-1 test. The projectile is in an ideal posture before hitting the target plate. The contact with the target plate begins at 5.28 ms. At 12.21 ms, about 2/5 of the length of the blade projectile has passed through the target, and, at 21.12 ms, the titanium-alloy projectile completely passes through the target. During the entire impact of the titanium-alloy blade projectile, the target plate undergoes limited bending deformation, which differs significantly from the case for impact by the gelatin projectile. This also explains the concentrated damage inflicted on the target plate and the low energy absorbed.  
Figure 9 shows the process of CFRP projectiles perforating a 2D triaxial braided target in a CFRP-3 test. At 0.42 ms, the CFRP projectile makes initial contact with the target plate, and, at 1.05 ms, it has almost passed through the target plate. The target plate undergoes no obvious bending deformation during the impact, and material is ejected from the back of the target plate due to matrix fragmentation.  
Figure 8: High-speed photographs of impact on 2D triaxial braided composite target plate of titanium-alloy projectile with an impact velocity of 105 m/s.  
Figure 9: Perforation of 2D triaxial braided composite target plate by carbon fiber-reinforced plastics (CFRP) projectile with impact velocity of 157 m/s (CFRP-3 test).