Numercial Simulation Of Impact Resistance Of Ceramic/Polyurea Composite Structures

Impact protection material is widely used in vehicle,ship and body armor.Impact protective material with excellent performance should not only be lightweight,but also have good comprehensive mechanical properties.Traditional homogeneous material obviously cannot meet the above requirements at the same time,so composite materials and structures have been widely studied.Ceramic has characteristics of low density,high hardness and high strength,etc.It is a commonly-used impact protection material,and is often used in protective armors of tank and military aircraft,but its high brittleness seriously restricts its wider application.Polyurea has the characteristics of low density,high toughness and good abrasion and impact resistance,and has good adhesion with metal and non-metal materials.Its applications to impact and explosion protection structures have attracted much attention in recent year.The composite application of ceramic and polyurea,giving full play to their performance characteristics,will provide a new feasible way for designing and preparing high-performance protective structure.This paper conducts research on the impact resistance of ceramic/polyurea composite structure based on numerical simulation.The problems existing in impact simulation of ceramic and its composite structure are first discussed,and suitable simulation schemes and parameters are determined.Then,the impact resistance of different ceramic/polyurea composite structures is analyzed systematically,and the influences of structure configuration,parameters and impact conditions on their impact resistance properties are obtained,which will provide guidance for the design of ceramic/polyurea composite structure.Specifically,the following works have been done:First,the smoothed particle hydrodynamics（SPH）method was used to simulate high velocity impact of a ceramic tile against a blunt tungsten heavy alloy projectile,and the simulation results were verified by experiment results.The performance of the SPH method and other methods were compared and analyzed.The effects of contact treatment and modeling parameters such as artificial viscosity and smoothing length in the SPH simulation were studied.The results show that the SPH simulation can reproduce the mushrooming deformation of the projectile’s head,the ejecta at the front face of the target and the bulging movement at the back face.The simulated deformation characteristics of the target are qualitatively consistent with the results observed in the experiment.Using reasonable parameters,SPH simulation can predict the residual velocity and residual mass of the projectile with good accuracy,and the prediction results are generally better than those of other existing methods.By comparing two contact treatment methods the penalty contact method（PCM）and the particle approximation method（PAM）,it is found that the simulation results of them show insignificant difference.Since PAM does not involve parameter selection,it is more convenient to use PAM to simulate high velocity impact of ceramic.The study on the effect of artificial viscosity shows that:the linear bulk viscosity coefficient（Q₂）has a greater effect on the residual velocity of the projectile,and the residual velocity decreases as Q₂ increases.In addition,it is found that:like finite element method（FEM）,the simulation results of SPH show sensitivity to the particle spacing,and the particle spacing sensitivity can be significantly reduced by using the same smoothing length and equivalent artificial viscosity.The content of this part indicates that SPH is suitable for simulating high velocity impact of ceramic by projectiles,but it is necessary to reasonably establish the model and determine the relevant parameters.This lays the foundation for determining the impact resistance of ceramic/polyurea composite structure with numerical simulation.Then,impact resistance of ceramic/polyurea layered plates was numerically studied with coupling technique of SPH and finite element method（FEM）.A SPH-FEM coupling model of the blunt-nosed projectile impacting on ceramic/polyurea layered plates with the same areal density as the above-mentioned ceramic tile is established.The effects of target configuration,interface state and polyurea layer thickness on the impact resistance of ceramic/polyurea layered structure were studied by numerical simulation.It is found that the layered plate with polyurea bonded on the back of the ceramic（configuration C2）has the best impact resistance,and are significantly better than ceramic target of equal area density.Through the study of the impact resistance of the thickness of the polyurea layer on the layered plates,it is found that when the total thickness of the polyurea layer increase from 6 mm to 10 mm in the bonded state,the impact resistance of the layered plate with equal thickness polyurea on the front and back of the ceramic（configuration C3）is significantly improved.In addition,except the thickness of the polyurea layer of the layered plate consisting of ceramic layer and covering polyurea layer（configuration C1）of 10 mm and 12 mm,the impact resistance of the bonded layered is better than that of the laminated layered plate.The impact resistance of C2 with different nosed shapes of the projectile normally penetrated and obliquely penetrated was studied.The results show that the target’s resistance to the impact of blunt-nosed,hemispherical-nosed,ogival-nosed and conical-nosed projectile decreases in order.The ricochet angles of these projectiles are all 75°,but the projectile with a curve shape can ricochet earlier than the projectile with a straight shape.The content of this part indicates that polyurea can effectively improve the impact resistance of ceramic,and the impact resistance of ceramic/polyurea laminate plates with reasonable configuration is significantly better than pure ceramic tile with same areal density.Finally,the impact damage characteristics and laws of nacre-like ceramic/polyurea composite structures were studied.Imitating“brick-mortar”nacre microstructure,and designing a nacre-like ceramic/polyurea composite beam.A finite element model of blunt-nosed projectile impact nacre-like ceramic/polyurea composite beam was established,and its impact damage characteristics and laws were analyzed,and compared with ceramic beam.The results show that at high velocity impact,the ceramic beam is damaged in an integrated manner,and the nacre-like composite beam has a small damage range and can better maintain good structural integrity,and has better the ability to resist multiple impacts.As the impact velocity increases,the damage range of the ceramic beam continuously increases,and the extent of damage is more severe.The damage range of the nacre-like composite beam does not change much after the impact velocity is higher than a certain value（50 m/s）,but only the extent of damage increases.In addition,as the size of the ceramic tile and the thickness of the polyurea layer in the beam are reduced,the damage range and damage extent of the nacre-like beam decreases.