Study On Bulletproof Performance Of Polyurea Reinforced Composites

Polyurea materials are of widespread use in the area of protection,helmet coating is a typical representative of its application in the area of military protection.As one of the main protective equipment of individual soldiers,bulletproof helmets are important in protecting the safety of soldiers’heads and have broad application prospects.This article is based on the lightweight and defensive enhancement of the aramid bulletproof helmet,starting from the enhancement of fragment protection and bullet protection performance,the goal is to improve the ballistic limit performance and reduce the backface signature.Firstly,the bulletproof performance test of aramid helmet body was carried out.Taking the coating position and thickness of polyurea material as factors,a series of test groups were designed.The impact tests of 1.1g standard simulated fragment and 51 pistol bullet（lead core）were carried out on the helmet body with different coating methods and five coating thicknesses,such as uncoated,coated on back,front and front/back.The bullet velocity is measured by the screen,the ballistic limit is calculated,and the backface signature is measured,then perform numerical simulation for test conditions,and analyze the bulletproof mechanism combined with the test results.The failure mode of helmet body,the influence factors of ballistic limit,the influence factors of bulletproof performance and energy absorption are studied through data comparison,data simulation and bulletproof mechanism analysis different coating methods and thickness of polyurea coating,the main conclusions are as follows:The ballistic limit of 1.1g standard simulated fragment and the test results of type51 pistol bullet show that:when the projectile penetrates into the helmet coated with polyurea at the test speed,the"shrinkage effect"exists in the holes of the polyurea coating on the front and back of the helmet,the aperture of the 1.1g fragment is 1/2～2/3of the fragment size,and the aperture of the type 51 pistol is 1/6 of the bullet caliber;the ballistic limit V₅₀of the fragment can be reduced by applying polyurea on the back of the helmet,and the V₅₀value is inversely proportional to the polyurea thickness,when the thickness is 5mm,the V₅₀value can be reduced by 16%.The ballistic limit V50 of1.1g standard simulated fragment can be increased by polyurea coating on the warhead surface,and the V₅₀value is proportional to the coating thickness.When the coating thickness is 5mm,the V₅₀value can be increased by 12%;The impact of the coating on the front/back surface on the ballistic limit V₅₀is not significant;The thicker the coating is,the lower the specific energy absorption（SEA）of the helmet body is.When the coating thickness is 5mm,the coating on the projectile facing surface decreases by about 21%,and other coating methods decrease by 52～56%;Polyurea coating on the helmet can reduce the backface signature of type 51 pistol bullet,and the backface signature is inversely proportional to the polyurea thickness,when the thickness is 5mm,the polyurea coating on the back and the front/back reduces by 82%～86%,and the backface signature on the front reduces by 34%.Based on experimental data and numerical simulation,the penetration process visualization is realized,and the penetration mechanism of polyurea coated helmet against two projectiles is analyzed,the results show that:Under the penetration of fragments and lead core projectiles at a certain speed,the polyurea coated on the front absorbs energy due to its strain rate effect,and has no significant effect on the energy dissipation of the helmet fiber,so it can improve the performance of the helmet against fragments and lead core projectiles;The polyurea coating on the back of the helmet has a limiting effect on the tensile deformation of the fiber and the delamination of the helmet body,which reduces the anti fragment performance of the helmet body,but is conducive to reducing the backface signature on the back caused by the lead core projectile..