Experimental Study On The Failure Characteristics Of Reactive Powder Concrete Impacted By Ogive-nose Projectiles

As a special kind of composite material,concrete structures are applied widely in the military defense works and airport runways due to its easy formability,good water and fire resistance,excellent durability,high strength and so on.And it will be the direct target of air strikes.Therefore,the study of failure characteristics of concrete structures after impact has important engineering application and military strategic value.In this paper,38 Cr Mn Si ogive-nose head,high and low strength projectiles and steel fibers reinforced reactive powder concrete(RPC)targets are taken as the main research objects,and the two-stage light gas gun was used to carry out the impact experiment.The penetration response characteristics after experiment under different impact conditions were studied and analyzed.The main conclusions are as follows:(1)According to the post-test projectiles and the targets after experiment,the failure behaviours of projectiles and targets in terms of three impact conditions were observed and analyzed.The penetration processes includes the conical crater stage due to the impact of projectile and the subsequent tunnel stabilization stage.Meanwhile,the radial cracks propagating outward on the surface of the target can be observed.As far as the damages of projectiles,there exists a small amount of mass loss for the impact condition of high-strength projectile,while it has a deformation or even blunting in projectile nose except for the mass loss when the low-strength projectiles impact RPC under the condition of high velocities.(2)According to the experimental data,the effects of initial impact velocity on the mass loss of projectile,the penetration depth and average crater diameter are analyzed.It is found that the mass loss and penetration depth increase with the increase of velocity in the case of high-strength projectile impact,and they show the similar parabolic variation rules in terms of low-strength projectile impact.The influence of initial impact velocity on average crater diameter is not obvious.(3)The friction action between projectile and target material is the main cause of mass loss of projectiles.For the impact condition of low-strength short-bar projectile,there exists a transition penetration mechanism between the rigid penetration regime and semi-hydrodynamic penetration regime once up to the critical impact velocity,which is mainly marked by the sudden drop of penetration depth and macroscopically reflected as the deformation of projectile nose.(4)It is an effective way to improve the impact and penetration performance of projectile by increasing the length-diameter ratio and ensure the higher diameter of projectile at the same time.The incorporation of steel fibers can effectively enhance the penetration performance of concrete structures.Compared with plain concrete,the penetration depth and average crater diameter of RPC decrease by about 27% and 32% on average respectively.It can be concluded that RPC is a kind of concrete material with excellent impact penetration performance.(5)F-model has poor applicability for predicting the penetration depth of RPC targets,while H-model has good applicability when the projectile is in rigid penetration regime.However,when the projectile is in the transition regime or semi-hydrodynamic penetration regime,the curves of two models cannot reflect the changing trend of actual penetration depth with the increase of impact velocity.