Bullet Impact Research Articles

Study on dynamic characteristics of transient high-speed water jet impacting into and out water

This research investigates the physical mechanism and dynamic characteristics of morphological evolution of transient high-speed water jet impacting target plates above and below the water layer. Two experimental systems were used to measure the jet velocity and wall pressure, capture the jet morphology under different conditions, and obtain the influence relationship between the water layer and the transient high speed water jet. A numerical method based on VOF was used to observe the morphological change process of the jet tip at the central section. When the jet does not pass through the water layer and impinges upward on the target plate in the air, the mushroom-shaped annular ligament and obvious tip are formed at the front of the jet. When the jet impinges on the target plate in the air through the water layer, a transient pulsed high-speed water jet is formed. When the jet impinges on the target plate under the water layer through the still air, the front end of the jet forms a tip with elevated curvature and short length. With the shift of the thickness of the water layer and the quality of the explosion, single-layer or multilayer tower tips, different forms of cavitation bubble groups and bullet impact ligament and other physical phenomena can be observed in the tip formation region. It is concluded that the water layer plays a crucial role in the dynamic characteristics of transient high-speed water jet.

Research on Energy Absorption Characteristics of Bouligand Biomimetic Structure Based on CFRP Composite Materials

Enhancing the impact resistance performance of carbon fiber-reinforced polymer (CFRP) laminates stands as a prominent research focus among various nations. Existing studies have shown a tendency towards arbitrary selection of the inter-ply helix angle values in CFRP laminates, which is accompanied by a limited number of samples representing the chosen helix angles. However, existing studies have shown a relatively random selection of spiral angle values between CFRP laminates, and the sample size of selected spiral angles is limited, posing certain limitations. In order to tackle this problem, we have employed a systematic arrangement of combinations to select the optimal helix angle for CFRP laminates. Inspired by the biological structures of Bouligand, we have sequentially chosen 19 distinct sets of helix angles, aiming to overcome the inherent limitations and enhance the research outcomes in this field. In this study, we established 19 finite element models to investigate the behavior of Bouligand-inspired CFRP composite panels under high-velocity bullet impact. The models were created by selecting 19 sets of helix angles within the range of 0 to 90° with a 5° interval. The results show that the energy absorption of the Bouligand layer-stacking composite plate is better than that of the conventional plate. The optimal spiral angles of the CFRP laminate are 25° and 30°, and the energy absorption characteristics of the laminate are the best at these angles. The impact resistance is also the best at these angles. The energy absorption of the Bouligand layer-stacking composite plate is 396% higher in absorbed internal energy and 361% higher in absorbed kinetic energy compared to the conventional layer-stacking composite plate, significantly improving the ballistic performance of the CFRP bulletproof material and providing a reference for the design of individual protection equipment.

Numerical Investigation on the Ballistic Performance of Semi-Cylindrical Nacre-like Composite Shells under High-Velocity Impact.

The nacre has excellent impact resistance performance, and it is attracting attention in the field of aerospace composite research. Inspired by the layered structure from nacre, semi-cylindrical nacre-like composite shells of brittle silicon carbide ceramic (SiC) and aluminum (AA5083-H116) were established. Two types of tablet arrangements (regular hexagonal and Voronoi polygons) of the composites were designed, and the same size of ceramic and aluminum shell were established for the impact resistance analyzed numerically. In order to better compare the resistance performance of the four types of structures under different impact velocity, the following parameters were analyzed including energy variation, damage characteristic, bullet residual velocity, and semi-cylindrical shell displacement. The results show that the semi-cylindrical ceramic shells have higher rigidity and ballistic limit, but the severe vibration after impact causes penetrating cracks, and the whole structure failure occurred eventually. The nacre-like composites have higher ballistic limits than semi-cylindrical aluminum shells, and the impact of bullets only causes local failure. In the same conditions, the impact resistance of regular hexagons is better than Voronoi polygons. The research analyzes the resistance characteristic of nacre-like composites and single materials, and provides a reference for the design of nacre-like structures.

Analysis of the Ballistic Performance and Mechanism of Soft Bulletproof Layers under the Impact of Multiple Lead Core Bullets

The soft bulletproof layers as key protective component of a bulletproof vest against pistol bullets, are subject to multiple bullets in both the ballistic resistance test and the real combat. To analyze the influence of multiple impacts on the ballistic performance, the ballistic tests are conducted on the soft bulletproof layers. The ballistic performance of multiple ballistic impacts is compared in the same test condition, and the influence of mechanical properties of materials, boundary effects, angular effects and structural changes caused by impact are studied. It is concluded that the ballistic protection performance of the multiply structure of soft bulletproof layers not only depends on the ballistic protection and energy absorption performance of the single-layer fabrics, but also is closely related to the ballistic protection synergy between the soft bulletproof layers; from the perspective of fibers and single-layer fabrics, the ballistic protection and energy absorption are determined by main factors such as elastic modulus, tensile strength, strength of materials and breaking strain, which also have the coupling effects; for the structural design of multiple soft bulletproof layers against lead cored bullets, it is necessary to comprehensively study the influence of mechanical properties of the projectile and target materials, boundary effects, angular effects and structures & forms on the ballistic protection performance.

Numerical studies on resistance of concrete target under rigid projectile impact using Perzyna-type visco-damage model

In this paper, a whole process resistance analysis of the concrete target impacted by the high-speed rigid projectile is presented. Combining the SPH method with the established rate-dependent Perzyna-type visco-damage constitutive relationship, the behaviors of concrete targets under rigid bullet impact are simulated, which is validated by test data. The investigation into the relationship between the acceleration and the velocity of rigid bullets reveals that the resistance of concrete under impact is composed of two parts: a velocity-independent static term provided by the solid component and a velocity power function term provided by the component that is converted into pseudoplastic fluid due to high-speed striking. Finally, the analytic formulae are built using the power-law resistance model, which can predict penetration depths at different initial velocities as well as the movement of the bullet.

Experimental Estimation of Energy Absorbed and Impact Strength of Kevlar/Basalt-Epoxy Interwoven Composite Laminate Added with Al2O3 Nanoparticles after High-Velocity Bullet Impact

The use of composites has increased exponentially in most industries, especially in the aerospace industry; the usage of composites has increased by almost 40% in the last 15 years. Aerospace components are often subject to high-impact loads, so it is important to use impact-resistant materials. Kevlar is known for its high-impact resistance and is commonly used as a fiber with various resins to achieve the desired properties. This paper mainly focuses on weaving Kevlar with basalt fiber in plain weave type by the traditional handloom weaving method. The epoxy resin, along with the harder, is then mixed with the aluminum oxide nanoparticles (Al2O3) in different percentages [1%-KB1, 3%-KB2, and 5%-KB3] to form the matrix. The laminate fabricated is then subjected to the high-velocity bullet impact of around 250 m/s. A steel hemispherical head projectile was used in the testing, and it was found to be penetrated through all the specimens making holes. The impact strength for all the different specimens was then estimated by calculating the bullet damage area and energy absorbed. The plate added with 3% Al2O3 nanoparticle was found to have improved impact strength when compared with the other two specimens. This plate can be used for bulletproof and other high-velocity impact applications.

Enchanching Body Armor: Evaluating UHMWPE with Contoured Surfaces for Improved Anti-Ballistic Performance using Finite Element Methods

Anti-ballistic is an indispensable personal protective equipment such as body armour for military and police personnel. This tool has received a lot of attention in recent decades due to increasing threats and insurgencies. Several studies have reviewed the development of anti-ballistic technology. However, there still needs to be discussion related to the development of anti-ballistics using UHMWPE (Ultra High Molecular Weight Polyethylene) and the contours of the surface of the UHMWPE. In addition, anti-ballistic studies are rarely carried out compared to other fields. This is because discussions or research related to weapons are still sensitive discussions. This study aims to determine whether the quality of body armour made using UHMWPE which one of the surfaces is given a specific profile, is better when compared to UHMWPE, which has no contours on all surfaces. UHMWPE material that is given a certain profile is one of the ideas chosen because it has high strength and aesthetic value, so it is expected to withstand bullet impact, comfortable and attractive when used. The antiballistic properties of UHMWPE given the diamond contour were obtained from numerical simulations using the finite element model (explicit dynamics) of ANSYS Workbench software. The two UHMWPE variants used in the multiplelayered configuration consist of UD UHMWPE sheets. Ballistic testing used a 7,62 mm calibre lead bullet with a velocity of 720 m/s. The material model of the bullet and UHMWPE plate used the Johnson-Cook plasticity model.

Functional gradation of aluminum alloy by impact of ballistics as severe plastic deformation process

In the present effort, impact of bullets fired at high speeds on a stationary target was used as a high strain-rate plastic deformation method to generate Functionally Graded Materials (FGMs). The bullet-shaped Aluminum alloy Al5052 specimens impacted the UHMWPE target at different projectile velocities ranging from 100 m/s to 750 m/s, to study the effect of the impact speed. Moreover, few of the projectiles impacted along the longitudinal axis whereas the remaining projectiles impacted with an obliquity to investigate the effect of leading-edge shape. The metallography of the projectile specimens fired at 750 m/s shows grain refinement from 70 ± 3 μm at the rear/ un-deformed point to 10 ± 1 μm at the front/ severely deformed point which is in the impact zone. Similar but of less magnitude variations were observed at other impact speeds also. The hardness variation was 45% (70 ± 3 HV at the rear surface to 102 ± 2 HV at the front face) at 750 m/s. Moreover, least variation in hardness and grain size was observed for projectile impacted at lowest velocity tested (100 m/s). Further, functionality in hardness and grain refinement was seen in graded direction due to shape of the projectile specimens, impact velocity, and target material. Depending upon the impact angles, axisymmetric (impacted normal to the longitudinal axis) or unsymmetrical (impacted at an angle) variation of grain refinement and hardness was observed.

Numerical Simulation of Penetration Process of Depleted Uranium Alloy Based on an FEM-SPH Coupling Algorithm

In order to quantitatively study the penetration capability of depleted uranium alloy, a simulation model of bullet impact on target plate with FEM-SPH coupling algorithm was established by using LS-DYNA software, which was combined with Johnson-Cook intrinsic model, Johnson-Cook fracture criterion, and equation of state to conduct a simulation study of alloy bullets made of depleted uranium alloy, tungsten alloy, and high-strength steel to penetrate target plate at 1400 m/s initial velocity. The results show that under the same conditions of initial kinetic energy, initial velocity, and initial volume, the residual kinetic energy of the depleted uranium alloy bullet is 1.14 times that of tungsten alloy and 1.20 times that of high-strength steel, and the residual velocity is 1.14 times that of tungsten alloy and 1.18 times that of steel, and the residual volume is 1.13 times that of tungsten alloy and 1.23 times that of steel after the penetration is completed. The shape of the bullet after penetrating the target plate is relatively sharp, and the diameter of the target hole formed is about 1.70 times the diameter of the projectile, which is significantly larger than 1.54 times that of tungsten alloy and 1.39 times that of high-strength steel, indicating the excellent penetration performance of depleted uranium alloy.

Polyurea-coated ceramic-aluminum composite plates subjected to low velocity large fragment impact

Research on high-velocity bullet impact resistance of composite plates has been widely used in bulletproof material field, but limited studies have focused on the response of composite plate under low velocity and large fragment impact. In this paper, the impact response of polyurea-coated ceramic-aluminum composite plate to low velocity and large mass fragment was experimentally and numerically studied. The fragments were launched using a self-designed launcher, which can realize the free flip impact test of low velocity and large mass fragments with flight speed of 100–300 m/s and the mass of 0–100 g. Based on finite element method and smooth particle hydrodynamics, the impact model of low-velocity large fragments on composite plates was established to study fragment deformation and composite plate damage and compared with the experimental results to verify the effectiveness of the model. The multi-angle impact response of the fragment on the composite plate was studied. Results indicated that unlike the high-velocity impact of traditional bullets, low-velocity and large-mass fragments will flip in varying degrees after hitting the target accompanied by the deformation of the fragments, which remarkably influence the impact penetration ability of the fragments. Moreover, with the increase of biting angle, the composite plates show enhanced energy absorption capacity.

Nature-inspired bamboo-spiderweb hybrid cellular structures for impact applications

Rapid increase in the operating speeds of aerospace/automobile vehicles has demanded for the design of light weight structures resisting high velocity impact loads. Cellular structures have shown significant potential for mitigating the effects of extreme loading. Due to its geometry, honeycomb structure is observed to possess the highest load carrying capacity as compared to other regular shapes. In this study, three different hybrid cellular structures, namely: design 2, design 3 and design 4, are designed and developed for impact applications, through a systematic study considering the hexagonal basic unit cell, and combining order and levels by mimicking bamboo-spiderweb structures. Parametric studies are performed and the proposed unit cell in design 4 is observed to demonstrate the best performance in terms of specific energy absorption and crush force efficiency. Analytical models are developed to estimate the energy absorption of unit cells in designs 2–4 during the impact. Numerical studies are performed considering the proposed unit cells to estimate the energy absorption characteristics. Results from analytical and numerical investigations are compared to notice a close agreement, with a maximum error of 9.97%. The resistance to local impact is tested by developing sandwich structures with cores developed from the proposed unit cells. Bullet impact studies are performed on the sandwich structures at three different identified locations with an impact velocity of 115 m/s. Design modifications are carried out by combining the multi-staging and strategically offsetting the unit cells in each core of a two core sandwich structure, such that it can withstand the impacts at arbitrary locations for bullet speeds up to 115 m/s. The proposed novel fourth order and third level hybrid unit cell in design 4 is found to efficiently resist the impact loads. Hence, it is recommended for applications involving energy absorption under extreme loads.

Flexible and lightweight Kevlar composites towards flame retardant and impact resistance with excellent thermal stability

The impact and thermal damage in extreme environments generally exist together. In this context, the design of safety protection materials ought to consider not only the single impact protection performance, but also thermal stability and flame resistance. In order to simultaneously achieve the impact resistance, thermal stability and flame resistance properties, a flexible and lightweight shear-hardened composite material (STF/Kevlar) was prepared by impregnating and drying shear thickening fluid (STF) on Kevlar fabric. Due to the favorable shear thickening performance of shear thickening fluid, STF/Kevlar composite material can increase the maximum yarn pull-out force of the fabric yarn from 3.3 N to 16.3 N with the impregnation weight gain of 55 wt%. Moreover, in bullet impact experiment, a single layer of STF/Kevlar fabric can nearly double the time it takes a bullet to penetrate pure Kevlar fabric. Additionally, STF/Kevlar composite material exhibits significant flame resistance as well. The limit oxygen index can reach 32 %, and after 30 min high temperature treatment at 400 °C, the composite still maintains good mechanical property and flexibility. This multi-functional composite material along with the performance of resisting both mechanical shock and thermal damage in extreme environments is expected to broadly apply in the field of lightweight protection.

A ballistic impact model for evaluating a preliminary higher level from simulation and tests on a glass fibber composite

This paper presents a discussion on simulating the impact projectile – target, for a velocity of 375 m/s and a comparison to actual stratified panels. Model is run in Explicit Dynamics (Ansys), with material constitutive models as isotropic bilinear hardening, the failure criterion being the equivalent plastic strain at break. Dependence on elastic properties of temperature is not available in simulations that use explicitly dynamic systems. Only one value is used for a property. These temperature dependent values will be used by the solver. The first values defined as temperature-dependent data will be used in numerical solving. In the case of projectile impact-protection panel, the use of properties without temperature dependence is justified by recordings with thermal cameras, by the results of models presented in the literature and the characteristics of the materials used for the panels, some of which (such as aramid or glass fibber composites), having constant properties over a fairly large temperature range. From the documentary study, the modelling of a bullet impact calibre (9 mm or 7.62) in the impact domain targeted by the author is analysed under isothermal conditions. There is a thermal effect, but it is considered weak as compared to the failure mechanisms of the involved solids (breaking, deformation, delamination, friction). There were simulated and tested panels made of 8 and 16 layers, considered bonded with breakable condition in tensile stress. The actual panels are made of quadriaxial fabrics of glass fibbers, bonded by laying-up and pressing with an epoxydic resin. From the results obtained for these runs, the following conclusions could be drawn: (I) although the layer material model was simplified to a isotropic bilinear hardening model with data from the literature, the results were validated by the number of layers destroyed for the partially penetrating plates and by the size of the delamination on the back of the last layer and (II) based on the results for panels modelled and actually tested, cases with intermediate thicknesses could be rolled in order to optimize the surface density of the protective panel.

Study on protective performance and gradient optimization of helmet foam liner under bullet impact.

Protective equipment in war plays a vital role in the safety of soldiers, the threat to soldiers from brain damage caused by deformation at the back of the helmet cannot be ignored, so research on reduce blunt post-cranial injury has great significance and value. This study first conducted gunshot experiments, used rifle bullets impact bulletproof plate and different density liner foam to record the incident process and internal response of craniocerebral model. After verifying the accuracy of finite element model through experimental data, optimization model is established based on response surface method to optimize the structure of gradient foam, analyze the cranial strain and energy absorption to select the best density and thickness distribution of each foam layer. Optimization results show that liner foam which designed to have lower density and thicker thickness for impact and brace layers, higher density and thinner thickness for middle layer can significantly improve the energy absorption efficiency. Compared to the 40.65 J of energy absorption before optimization, the optimized gradient foam can absorb 109.3 J of energy, with a 169% increase in the absorption ratio. The skull strain in the craniocerebral model was reduced from 1.260 × 10–2 to 1.034 × 10–2, with a reduction of about 22%. This study provides references for the design and development of protective equipment and plays an important role in ensuring the safety of soldiers in the battlefield environment.

Research on performance of PBT/Bu-NENA low-vulnerability propellant

Large-size program temperature controller was used to carry out the slow cook-off test study of PBT, Bu-NENA, PBT/Bu-NENA mixture and PBT/Bu-NENA propellant in the range of gram and kilogram scale. The comprehensive performance of PBT/Bu-NENA propellant was carried out evaluation, including energy performance, mechanical performance, and low vulnerability performance (including fast cook-off test, slow cook-off test, shaped charge jet impact test and bullet impact test). The test results show that the slow cook-off response temperature of gram-weigh PBT, Bu-NENA and PBT/Bu-NENA mixture are 178.5°C, 142.3°C, and 139.0°C, respectively, while that of kilogram-weigh PBT/Bu-NENA propellant is 121.9°C. Analysis believes that high volatility of Bu-NENA plasticizers the main reason for the response temperature to drop from 139.0°C to 121.9°C. The PBT/Bu-NENA propellant has low vulnerability characteristics. Among them, the shaped charge jet impact test has the highest degree, which is an explosive reaction, and the sympathetic detonation test has the lowest response degree, which is below the burning. The theoretical special impulse of the PBT/Bu-NENA propellant is greater than 267 s,the density is greater than 1.80 g/cm3, the glass transition temperature (Tg) is less than -66°C, and the mechanical properties in the range of -60°C ∼ +70°C are excellent.

Experimental analysis of ballistic trauma in a human body protected with 30 layer packages made of biaxial and triaxial Kevlar® 29 fabrics

Behind armour blunt trauma (BABT) is a body injury resulting from the deformation of the back surface of armour as a result of a bullet impact. In the case of textile body armour, the severity of the injury may depend on the material of the fibres, but also on the geometric structure of the fabric. The article focuses on experimental research into injuries of the human body protected by ballistic packets made of biaxial and triaxial fabrics, during a non-penetrating impact from a Parabellum 9 mm × 19 mm Full Metal Jacket (FMJ) bullet, at a speed of 406 ± 5 m/s. In experimental research, the fabrics had a comparable surface weight and were made of the same Kevlar® 29 yarn. The ballistic packages were made of 30 layers. As part of the work, a physical model of the human body was developed. The human body model consisted of a model of the heart, lungs, and skeletal and muscular systems. During the bullet impact, the pressure forces were recorded using sensors located at selected points of the human body. The bullets hit five selected places on the body that were considered critical, from the point of view of maintaining a human’s vital functions. It was found that, during firing, pressure increases both at the site of impact and in the internal organs, which can lead to multi-organ damage. As a result of the experimental analysis, it has been shown that the pressures exerted on specific organs are always lower in the case of body protection with a ballistic packet made of triaxial fabrics, compared to a packet made of biaxial fabrics.

Distinctive Bullet Impact Holes by 9-mm Caliber Projectile on Sheet Metal Surfaces

Distinctive Bullet Impact Holes by 9-mm Caliber Projectile on Sheet Metal Surfaces

A novel simple traumatic brain injury mouse model

BackgroundTraumatic brain injury, one of the leading causes of death in adults under 40 years of age in the world, is frequently caused by mechanical shock, resulting in diffuse neuronal damage and long-term cognitive dysfunction. Many existing TBI animal models revival with expensive equipment or special room are needed or the processes of operations are complex and not easy to be widely used. Therefore, a simpler TBI model needs to be designed.MethodsOur TBI model is an innovation of the modeling method through air guns shutting rubber bullets. A core facet is the application of our designed rubber bullet impact device. It could focus the hitting power to the fixed site of the brain, thus triggering a mild closed head injury. Moreover, the degree of damage can be adjusted by the times of shots.ResultsOur model induced blood-brain barrier leakage and diffused neuronal damage. Besides, it led to an increased level of Tau phosphorylation and resulted in cognitive dysfunction within several weeks post-injury.ConclusionOur TBI model is not only simple and time-saving but also can simulate mild brain injuries in clinical. It is suitable for exploring pathobiological mechanisms as well as a screening of potential therapies for TBI.

The finite element method-based pattern recognition approach for the classification of patient-specific gunshot injury.

Violence related injuries and deaths mostly caused by firearms are a major problem throughout the world. Understanding the factors that control the extent of hard-soft tissue wound patterns using computer imaging techniques, numerical methods, and machine learning algorithms may help physicians to diagnose and treat those injuries more properly. Here, we investigate the use of computational results coupled with the pattern recognition algorithms to develop an approach for forensic applications. Initially, computer tomography (CT) images of the patient whose leg was shot by a 9 × 19 parabellum bullet are used to construct the FE models of that patient's femoral bone and the surrounding soft tissues. Then, Hounsfield units-based material properties are assigned to elements of the bone. To simulate the full range of loading conditions encountered in ballistic events, a constitutive model that captures the strain-rate dependent response is implemented. The entrance pathway vector of the bullet is directed in accordance with the patient's wound and the simulations are deployed for the cases having various inlet velocities such as 150, 200, 250, 300, and 350 m/s. Once the FE results for each case are obtained, they are processed with supervised machine learning algorithms to classify the wound and inlet velocity correspondence. The results demonstrate that they can be diagnosed with a percent accuracy of 97.3, 97.5, and 98.3 for the decision tree (DT), k-nearest neighbors (kNN) and support vector machine (SVM) classifier, respectively. This approach may provide a useful framework in classifying the wound type, predicting the bullet impact velocity and its firing distance.

Fitness analysis of experimental results and finite element simulation results about bullet velocity based on ABAQUS simulation for impact of three dimensional woven reinforced composite

Four layers of glass fiber filaments with the fineness of 2400 tex were used as warp yarns, five layers of glass filaments with the fineness of 600 tex were used as weft yarns 110 tex and aramid fibers were used as Z yarns to process a three-dimensional woven reinforcement. Then, 307-3 unsaturated polyester resin was used as the matrix, and the three-dimensional woven reinforced composite was prepared by the VARTM method (resin transfer molding method). The bullet impact composite was modeled by ABAQUS (Finite element software). The starting conditions of the bullet incidence and the actual conditions were set consistently to analyze the change of the remaining velocity and acceleration of the bullet and the worth energy loss after the bullet impact. The results showed that the theoretical and experimental values of bullet incidence velocity and residual bullet velocity were linearly related. When the impact velocity of bullet incidence was higher, the slope of the straight line of the initial phase of bullet velocity decrease was larger, and the peak of the absolute value of acceleration after bullet impact was larger. The calculated value of energy loss after bullet impact simulation is basically consistent with the experimental value, This also fully proved that the bullet impact composite material model established was correct and effective.