## 1 Introduction  
After experiencing the war in the Middle East, the war in Iraq, and the war in Asia, military drones have developed into two categories encompassing sixteen types [1; 2; 3]. With the continuous integration of cutting-edge scientific and technological achievements, military UAVs have greatly improved in terms of flight control, detection, stealth, penetration, and fire strike. In recent years, this research on UAVs has made great progress in the direction of lightweight design. Nowadays, many structural parts of military UAVs, including parts, basically adopt lightweight honeycomb sandwich structures and composite materials. The 'Predator' UAV fuselage developed by General Atomics uses a large number of carbon fiber unidirectional prepregs and honeycomb sandwich structures. At the same time, carbon fiber beams and ribs are added to reduce the overall fuselage weight while ensuring strength. Its improved 'Death' uses the same fuselage structure but adds a new hybrid fiber prepreg. The 'Shadow' UAV produced by the AAI company uses a large number of reinforced epoxy resin structure skins and honeycomb sandwich structures, and the total application amount exceeds 95% of the body structure. More than 90% of the body structure of the X-45 UAV developed by Boeing Company uses a low-temperature curing prepreg and foam sandwich structure [4; 5; 6; 7; 8; 9]. At present, the weapons for typical targets in the air mainly include blast weapons, discrete rod warhead weapons, shaped charge warhead weapons, laser weapons, etc. The damage elements are mainly fragments, explosively formed projectiles, shaped charge jets, shaped charge rod penetrators, discrete rods, and other high-speed penetrators. Fragment penetration experiments are one of the main means to test the damage performance of composite structures and composites. Due to the different penetration speeds, it is generally divided into low speed, high speed, and ultra-high speed. The high-speed fragment penetration experiment is a common method for range testing. The initial velocity of the fragment is between 50 m/s-5000 m/s, which is used to analyze the flight attitude of the fragment, the power of the fragment, the failure mode, and the anti-elastic performance of the structure. From this research on the composite honeycomb sandwich structure, the commonly used methods are static compression and low-speed collision. However, there are few studies on the energy absorption characteristics and damage modes of the structure under high-speed conditions. With the different application scenarios, the structural protection requirements are also different. In particular, it is necessary to analyze the damage characteristics of high-speed fragment penetration structures. The progress of theoretical analysis has promoted this research on honeycomb structure from the whole to the micro [10]. In the past, the commonly used theoretical analysis was to equivalentize the composite honeycomb sandwich structure into a laminated plate and then carry out the relevant theoretical damage calculation according to the characteristics of the laminated plate [11]. With the deepening of research, the honeycomb sandwich structure has gradually transitioned from the common equivalent analysis method to the level of quantitative analysis of the structure itself [12; 13; 14; 15; 16]. For honeycomb structures, the commonly used analysis methods are static compression, ballistic damage, and explosion shock. In the static compression state, the compressive strength is much smaller than the compressive strength under dynamic load. The plastic deformation area of the honeycomb structure is near the contact area between the sandwich structure and the penetrator, and its damage is mainly concentrated inside the specimen. During the penetration process, the structure is more likely to be destroyed, resulting in fiber breakage, debonding delamination, and even perforation. [PERSON] et al.