Optimization And Ballistic Performance Of A Bio-inspired Scale-like Flexible Protection Device

Although the global situation is generally peaceful and stable,local terrorism and wars occur from time to time.Terrorist attacks are more and more covert,making the peacekeeping tasks become more and more serious.Soldiers are always facing life threats,greatly increasing the demand for protection system.However,most of the existing protective systems are large and single-function,with poor comfort and flexibility.In order to solve this problem,making the protective system develop to the direction of lightweight and multi-function,this paper drew inspiration from the hierarchical structure and overlapping pattern of the teleost fish（such as Grass carp,Cyprinus carp,Crucian carp,etc.）,designed and prepared a new type of bio-inspired flexible protection system with both bulletproof and flexible performance.Based on the basic principle of structural bionic design,the optimization of composite scales was conducted to improve the flexibility and deformation ability of the protection system while ensuring the its ballistic performance,increase the fitness of the soldiers,and improve the survival probability of combatants.In this paper,the structure of a single composite scale was designed,and the bio-inspired flexible protection system was prepared and optimized according to the overlapping pattern of fish scale.The ballistic limit and flexibility performance of the protection system were tested and systematically analyzed based on experimental study and finite element numerical simulation.This paper could provide scientific guidance for the design,optimization and application of the protective system.The main results could be drawn as follows:（1）According to the principle of bionic design,the double-arc composite scales were designed based on the hierarchical structure and overlapping pattern of the teleost fish scale.The spatial structure of the flexible protection system was analyzed,the relationship between the overlapping angle and the tilt angle was derived,and the arrangement of the composite scales was determined.In combination of experimental study and numerical simulation,the comprehensive properties of the commonly used ballistic materials were analyzed from the aspects of ballistic resistance and molding process of the protection system.Ultrahigh molecular weight polyethylene（UHMWPE）,Si C and Al₂O₃ ceramics were adopted to prepare the bio-inspired flexibility protective system.（2）According to the level II requirement of the standard"Requirements of the safety technical performance for military bullet-proof vest"（GJB 4300A-2012）,51type 7.62 mm pistol bullet（lead core）with initial velocity of 445 m/s±10 m/s was used to investigate the bulletproof performance of protection system with different materials and overlapping patterns.In order to study the influence of materials on the ballistic performance of the protection system,two kinds of flexible protection system,which were composed of Si C-UHMWPE and Al₂O₃-UHMWPE composite scales were prepared.The influence of the overlapping angles（i.e.70°,80°,90°）on the ballistic performance of the protection system were considered,and its failure area of after bullet impact was divided and analyzed.Results showed that the designed bio-inspired protection system could effectively resist the penetration of the bullet,and region II was the worst area which easily damaged during the bullet impact.In addition,the bulletproof properties of the protection system increase with the increase of the overlapping angle,and the ballistic performance of Si C ceramics was better than that of Al₂O₃ ceramics.Based on the analysis of the failure of scales,its dynamic response during the bullet impact was discussed,and the synergistic relationship between the composite scales was demonstrated.The flexible deformation ability of the bio-inspired protection system was measured,results were satisfactory,indicating that the deformation of the protection system is more than 12mm when it subject ed to50N load.（3）ANSYS/Ls-dyna finite element software was used to simulate the performance of the bio-inspired protection system during the impact of the bullet.The protection system model was established and dynamic penetration was carried out.The stress distribution of the protection system was analyzed,the process of the bullet damage was described,and the synergistic effect between the composite scales was explored and discussed.The simulation results were in good agreement with the experimental results.This paper provided important reference value for the design and application of the bio-inspired protection system.