Bullet Impact Research Articles

Multimaterial ballistic solutions for UAVs

One of the main challenges for UAVs (Unmanned Aerial Vehicles) used in defence and military operations is to effectively conclude a flight mission in a harsh environment. The platform survivability is critical, therefore it is imperative that the vehicle is able to withstand ballistic impacts in flight and still be able to reach its destination. In the present work, the authors discuss the development of a lightweight ballistic armour to protect critical areas of the vehicle, such as the control systems and/or the payload. The structure response during and after a 9 mm bullet impact, shows that the proposed hybrid composite panels will be able to withstand high-energy ballistic impacts after optimization. The FEA (Finite Element Analysis) method is implemented to study the performance of ceramic protective plates attached to the CFRP (Carbon Fibre Reinforced Polymer) structural platform. An Eurelian-Lagrangian modelling technique is implemented with different damage models for the various materials involved in the impact event in order to properly capture each material response in this complex load scenario. Numerical studies are validated experimentally. The base structural CFRP is cured in autoclave followed by a post-cure to integrate the remaining components. Experimental tests were conducted at a shooting range where 9 mm projectiles are fired at a distance of 10 m of the target plates. Data is collected recurring to a chronograph/high speed camera combination apparatus to measure the impact and residual velocity and the projectile deformation/damage. Numerical models show good correlation with the experimentally measured data.

Finite element model validation for a 14.5 mm armor piercing bullet impact on a multi-layered add-on armor plate

For armor plates testing and evaluation the use of modeling and simulation tools, together with a validated finite element model is a reliable approach in respect to a firing conducted session. The paper presents the validation of an advanced finite element model on the impact between two 14,5 mm armor piercing bullets with a multilayered add-on armor plate made by aluminum alloy, alumina tiles, aramid fabric woven, ultra-high molecular weight polyethylene fiber composite and a steel plate. An 8 mm thick armor steel witness plate was placed at 2 cm behind the add-on plate. The real tests were conducted in a firing range and a chronograph was used to measure the values of the bullet impact velocities. The test results showed that the first bullet penetrates the witness plate and the second bullet only deforms it. A three-dimensional finite element model of the bullet and armor plates was conceived to perform the impact simulations in LS-DYNA. Tensile and compression tests, as well as other scientific methods were employed to establish the strength and failure model parameters for each material. The results of the finite element model follow the experimental ones regarding the yaw angle assumptions that were applied for a simulation scenario.

Ballistic Impact Analysis of Graphene Reinforced Kevlar-29 and Kevlar-129 Laminated Composites

Aircraft goes through various high-speed hindrances like bird attacks, etc. Kevlar is increasingly used in the aviation industry to overcome such hindrances. Kevlar, an organic fibre from the family of aromatic polyamides consists of Kevlar 29, Kevlar 129, Kevlar 49 and Kevlar 149. This paper focuses on the use of Kevlar 29 and Kevlar 129 due to its low stiffness in comparison with Kevlar 49 and Kevlar 149. When pure Kevlar 29 and Kevlar 129 with 20 layers each are impacted with a 9g bullet at 900m/s velocity, the bullet perforates the laminate completely. Hence, the Kevlar layers are reinforced with graphene nanoplates. The bullet impact simulation of the ‘single-layer Kevlar 29 reinforced with single-layer graphene nanosheet’ (K29G), ‘single layer Kevlar 129 reinforced with single-layer graphene nanosheet’ (K129G), ‘double layer Kevlar 29 reinforced with double-layer graphene nanosheets’ (KK29GG) and ‘double layer Kevlar 129 reinforced with double-layer graphene nanosheets’ (KK129GG) is carried out using LS-DYNA. Maximum principal stress, effective stress, absorbed energy and displacement of the composite laminates (K29G, K129G, KK29GG and KK129GG) are used to compare the performance of these four laminates in the targeted applications. Due to its higher maximum principal stress, effective stress and lower displacement, the composite laminate K29G proves to be the apt laminate for its usage in aircrafts.

Whole genome sequence of bacteremic Clostridium tertium in a World War I soldier, 1914.

Dental pulp, encapsulating a blood drop, could be used to diagnose pathogen bacteraemia in archaeological materials using DNA-based techniques. We questioned the viability of such ancient pathogens preserved in ancient dental pulp. After meticulous decontamination of 32 teeth collected from 31 World War I soldiers exhumed in Spincourt, France, dental pulps were extracted and cultured under strict anaerobiosis. Colonies were identified by mass spectrometry and whole genome sequencing. Fluorescent in situ hybridisation (FISH) was used for the direct microscopic detection of pathogens of interest in the dental pulp. All the experimental procedures included negative controls, notably sediments in contact with individual SQ517 to ensure that results did not arise from contamination. Clostridium tertium was detected by FISH in two dental pulp specimens taken from a 1914 soldier. After a two-day incubation period, both dental pulp samples grew colonies identified by mass spectrometry and genome sequencing as C. tertium; whereas negative controls remained free of C. tertium in all the observations, and no C. tertium was founded in sediments. Skeletal remains of this soldier exhibited two notches in the left tibia evocative of a cold steel wound, and a probably fatal unhealed bullet impact in the hip bone. Data indicated the presence of C. tertium in the dental pulp at the time of the death of one World War I soldier, in 1914. This observation diagnosed C. tertium bacteraemia, with war wounds as the probable portal of entry for C. tertium. Our C. tertium strains ante-dated by three years, the princeps description of this deadly opportunistic pathogen.

Advanced functional Kevlar composite with excellent mechanical properties for thermal management and intelligent safeguarding

Fabric-based personal thermal management devices propel the development of flexible heaters which play important roles in medicinal therapy and protecting humans from cold environments. However, due to the poor mechanical properties, most heaters are easy to be damaged under dynamic loading forces, and also difficult to provide necessary anti-impact protection for human beings. Therefore, it is significant to develop multifunctional fabric heaters with high mechanical properties. Herein, a novel MXene/SSG/Kevlar-based multifunctional textile composite (MS-Kevlar) with sensitive monitoring, thermal management and impact protection is developed by assembling Kevlar fiber, shear stiffening gel (SSG) and two-dimensional MXene. This MS-Kevlar has high sensitive monitoring properties to various stimuli from slight physiological activities to high-speed bullet impact. MS-Kevlar with excellent conductivity shows high thermal management properties which can reach 80.9 °C at 6 V working voltage. Besides thermal protection property, the multifunctional MS-Kevlar can absorb 55.4% force under low-speed impact and still retain the electro-thermal performance after impacted. More importantly, the ballistic limit velocity of MS-Kevlar increases more than 142.1% compared with that of neat Kevlar which could provide safeguarding for humans. Finally, a smart curtain with thermal and anti-impact performance was designed and the based wireless impact alarm system is beneficial for people to assess and avoid dangers.

Experimental and numerical study on the ballistic performance of ultrahigh molecular weight polyethylene laminate

AbstractUltrahigh molecular weight polyethylene (UHMWPE) fiber orthogonally laid laminate is widely used in ballistic protection due to its excellent properties. Research on its response under bullet impact is meaningful for understanding the antiballistic mechanism and designing personal protection. In this article, three‐dimensional digital image correlation measurement and analysis method is applied to study the response of UHMWPE orthogonally laid laminates under the impact of pistol bullets. A corresponding smoothed particle hydrodynamics (SPH)–finite element method coupled numerical model is established to study the impact phenomenon. The bullet model is developed using the SPH method. The laminate is developed with multiple equivalent sublaminate finite element models. The experimental results show the damage mode and back‐face features of the laminate. First, the damage mode has two stages: the first stage includes a small number of layers that are penetrated on the impact surface and the second stage includes the expansion of the back‐face deformation. Second, the average maximum bulge height in three repeated experiments is 14.59 mm. Third, the average maximum velocity of the bulge apex position in experiments on the z‐axis is 92.32 m/s. Fourth, the maximum and minimum back‐face in‐plane shear values are 0.0893 and −0.0928, respectively. Finally, the numerical results have good agreement with the experimental results and show that the compression waves mainly propagate along the x and y directions. The experimental results can provide quantifiable features for studying the impact responses of UHMWPE laminates. The numerical model could be applied to study features that cannot be measured by experiments.

Ballistic Performance Evaluation of Kevlar-Glass Fibre Hybrid Composite Laminate against Medium Velocity Impact

In this paper, the post ballistic impact behaviour of kevlar-glass fibre hybrid composite laminates was investigated against 9×19 mm projectile. Eight different types of composite laminates with different ratios of kevlar woven fibre to glass fibre were fabricated using hand lay-up with epoxy matrix. Ballistic behaviour like ballistic Limit (V50), energy absorption, specific energy absorption and Back Face Signature (BFS) were studied after bullet impact. The results indicated that as the Percentage of glass fibre is increased there was a linear increment in the ballistic behaviour. Addition of 16% kevlar fabric, composite sample meets the performance requirement of NIJ0101.06 Level III-A. Since the maximum specific energy absorption was observed in Pure Kevlar samples and the adding of glass fibre increases the weight and Areal Density of the sample, further investigations need to be carried out to utilize the potential of glass fibre for ballistic applications.

Ballistic performance of composite structure configurations with high elongation calendered rubber layer laminated to AA5083-H112 aluminum alloy

This study aims to determine the ballistic performances of laminated composite plates produced with AA5083-H112 series aluminum and rubber material with high elongation capacity under impact loading. To investigate the effect of rubber compounds, two types of rubber with calendered and damping were prepared. Thanks to the surface treatment applied to the aluminum plates, the rubber–metal adhesion strength was adjusted, and four different laminated composite plate samples were prepared. Calendered rubber was used on the bullet impact surface of all samples, and damping rubber was used on the back. It has been observed that the pressure barrier created by the calendered rubber bullet on the front face provides high performance to absorb energy. A detailed study was carried out on the total thickness of laminated composite plates, the interface adhesion strength between rubber and aluminum layers, and the ballistic performance of aluminum-rubber combinations. It was concluded that the laminated composite plate’s energy absorption would increase, especially by increasing the thickness of the dumping rubber layer on the back of the aluminum sheets. In the strong metal-rubber interface interaction between the rubber and aluminum layer, the bullet is stopped before the pressure barrier is formed. The penetration depth and bulging height increase, and most of the energy are transmitted through the aluminum plate. In the weak metal-rubber interface interaction, a significant portion of the energy is absorbed by the rubber and air thanks to the pressure barrier.

The lead-in method for bullet impacts in metal panels

The use of trajectory rods at shooting scenes to document a bullet’s trajectory is useful since the probing method provides for an immediate visual reference as to where the projectile came from and where it may have been traveling to. Trajectory rods are also quite simple to measure with manual tools. However, the use of trajectory rods is not always possible because a bullet may strike a relatively thin material, such as a metal panel, creating a bullet impact that is not suitable for determining the bullet’s path using the probing method. In these cases, it may be possible to use the elliptical method or the lead-in method. The ellipse method has been shown to have some of its own challenges when the bullet impact site is highly deformed while the lead-in method is less studied and only useful over lower ranges of impact angles. This study looks to define the lead-in method and then test its performance with 15 blind participants and 5 different calibers, each with two different types of ammunition. The results of this study have shown that each combination of caliber and ammunition has its own characteristic error curve that appears to change with the known impact angle. Errors do not remain constant and in some cases, the errors exceed 20°. The range of errors is greater at higher angles of incidence where the lead-in area is relatively small. The procedures outlined in this study propose a method of use, highlight limitations, and provide insight into the accuracy for the lead-in method.

Preparation and Properties of NC/TATB/Bu‐NENA/TMETN Low Sensitive Gun Propellants

AbstractSafety improvements in the field of energetic materials promoted the development of insensitive gun propellants. A low sensitive gun propellant was prepared by traditional extrusion using nitrocellulose (NC) as a binder, 1,3,5‐triamino‐2,4,6‐trinitrobenzene (TATB) as insensitive solid energetic filler, N‐butyl‐N‐nitramine (Bu‐NENA) as insensitive plasticizer, trimethylolethane trinitrate (TMETN) as co‐plasticizer, and graphite as thermal conductive filler. The density of gun propellants obtained was 1.611 g ⋅ cm−3 which was almost equaled to the theoretical density of 1.615 g ⋅ cm−3. The gun propellants exhibited excellent mechanical properties, especially cryogenic mechanical property, with the impact strength of 12.4 kJ ⋅ m−2 and the compressive strength of 157.1 MPa at −40 °C. The closed bomb test was conducted to investigate the energy and combustion performance. The results showed that the gun propellants had stable and regular combustion properties at a pressure up to 600 MPa. The burning rate pressure index n was about 1, and the impetus f and covolume α were 1045 kJ ⋅ kg−1 and 0.9764 cm3 ⋅ g−1 respectively. The vulnerabilities of the prepared gun propellants were evaluated by bullet impact, fragment impacts, sympathetic detonation, fast cook‐off, and slow cook‐off tests. The results showed that no response that was more severe than burning in test bombs was observed in bullet impact, fast cook‐off, and slow cook‐off tests under the given conditions. Moreover, a partially combustion reaction occurred in the fragment impact test with no obvious burning reaction in the sympathetic detonation test. It demonstrates that the prepared gun propellants possess good low vulnerability characteristics.

Experimental study on the protective performance of bulletproof plate and padding materials under ballistic impact

With the upgrading of protective equipment, the penetration ability of bullets into protective equipment is reduced, and the problem of non-penetrating brain injury caused by bullet impact becomes prominent, but related experiment is still rare. Therefore, this study establishes a human head surrogate model with anatomical structure, and then an experimental study on the dynamic response of cranial model protected by bulletproof plate impacted by 5.56 mm rifle bullet was conducted. The influence of bulletproof plate and padding material (type and density) on the head protection performance is analyzed. The results show that the acceleration of the front of the skull is reduced by 600 times with the protection of pad. At the density of 30 kg/m3, the protective effect of EVA (Ethylene-Vinyl Acetate copolymer) foam is better than that of EPP (Expanded polypropylene), the peak acceleration at the front of the skull is reduced by 36%. As the density of EVA foam increases, the acceleration of skull and the peak intracranial pressure increase, which can be judged that the brain injury would be aggravated according to the existing injury criteria. The study has important guiding significance for the design of protective equipment and the mechanism of cranial injury.

Ballistic impact response of resistance-spot-welded (RSW) double-layered plates for Q&P980 steel

Ballistic impact response of resistance-spot-welded (RSW) double-layered (2 × 1.6 mm) plates (190 mm × 150 mm) for Q&P980 steel impacted by a round-nosed steel bullet (12 mm diameter and 30 mm length) was investigated by using gas gun and high-speed camera system. The RSW specimens were spot welded using a 6 mm diameter electrode face producing a 7.2 mm diameter fusion zone of the spot weld. The ballistic curve and energy balance for the tests of the spot weld of the RSW specimens at different velocity were analyzed to characterize the ballistic behavior of the RSW specimens under bullet impact. The fracture mechanisms of the RSW specimens under bullet impact were presented. For the tests below the ballistic limit, the cracks initiated from the notch-tip and propagated along the faying surface or obliquely through the thickness depending on the impact velocity. For the tests above the ballistic limit, the plug fracture in the front plate of the RSW specimen could be caused by the thinning-induced necking in the BM near the HAZ, while the plug fracture in the rear plate of the RSW specimens may be consist of the circumferential cracking from the rear surface and the bending fracture of the hinged part of material. The effects of the electrode indentation and the weld interfaces on deformation and fracture of the RSW specimens under bullet impact were revealed. For the tests above the ballistic limit, the circumferential fracture from the rear surface of the RSW specimens was always initiated along the interior periphery of the electrode indentation and the crack paths were along the FZ/CGHAZ or CGHAZ/FGHAZ interface. When the circumferential crack also formed outside the electrode indentation, the fracture on the BM/HAZ interface could be found. On the front plate of the RSW specimens, the shear/bending induced cracking from the notch-tip were observed and the crack paths were along the FZ/CGHAZ or CGHAZ/FGHAZ interface.

An efficient energy characteristics and explosion heat improving method of FOX-7-based aluminized explosives

Exploring new composite explosives based on 1,1-diamino-2,2-dinitroethylene (FOX-7) is significant in the field of insensitive high explosives (IHE). Despite having good detonation performance compared to RDX, FOX-7 has not been successfully applied in the preparations of aluminized explosives due to the poor explosion heat values. In this paper, the explosion heat and detonation velocity of FOX-7-based aluminized explosives were studied systematically. The experiment results showed that the explosion heat of FOX-7-based aluminized explosives are significantly lower than that of RDX-based ones, especially when the content of aluminum powder exceeds 30%. To solve this problem, a simple but effective method of adding RDX to FOX-7-based aluminized explosives was developed, leading to a huge growth of explosion heat values. Finally, in order to compare the safety performance with RDX-based aluminized explosives, the low vulnerability of the FOX-7/RDX-based aluminized explosives formulation was investigated by fast cook-off, sympathetic detonation and 12.7 mm bullet impact tests. The results showed that the safety performance of FOX-7/RDX-based aluminized explosives is better than that of RDX-based aluminized explosives, proving that good low vulnerability is kept with the addition of RDX into FOX-7-based aluminized explosives.

Enhancement Data In Term Of Material Selection And Design Consideration For Bulletproof Vest

Bulletproof vest is also known as ballistic vest and it is used to provide ballistic protection to the body of law enforcement and military personnel from injury through bullet impact, fragments, stab attacks and other treats. In this project, shear thickening fluid/ultra-high molecular weight polyethylene, STF/UHMWPE fabrics composites were prepared in order to design a low cost and lightweight bulletproof vest with high mechanical properties (impact energy and stab resistance). There are 2 categories that are prepared (UHMWPE with and without STF) and each category has 10 different numbers of layers. For the “UHMWPE with STF”, 10 of them were impregnated with shear thickening fluid that prepared by sonochemical method by mixing dry silica nanopowders, polyethylene glycol and ethanol. The effects of number of layers of UHMWPE fabrics and STF/UHMWPE fabrics on the impact properties for both UHMWPE without STF and UHMWPE with STF fabrics were investigated by using drop tower impact testing. Results from this study showed, absorption of impact energy is increased with increase in the number of penetrated witness papers. Besides, it is also indicated that the impact energy absorbed by witness paper/s is increased when the number of UHMWPE fabric and STF/UHMWPE layers are increased. The comparison between 2 categories is discussed. The result showed that STF/UHMWPE fabrics have better performance than UHMWPE fabrics in term of impact energy absorption, stab resistance and number of fabrics layers.

Experimental study on deformation and fracture of resistance-spot-welded (RSW) overlapping plates impacted at RSW joint by round-nosed bullet

The ballistic tests of Q&P980 resistance-spot-welded (RSW) overlapping plates impacted at RSW joint by round-nosed bullet were performed using a single-stage gas gun system with a laser velocity interferometer system for any reflector (VISAR). The deformation and fracture mechanism of the RSW specimens were investigated by using the VISAR measured results, the metallographic cross-section observation and the scanning electron microscope (SEM) analysis of the recovered RSW specimens. The dynamic response of the RSW specimens was related to the reflection and refraction of the impact stress waves on the material interfaces and the free surfaces in the RSW specimens. The bulging, dishing, shearing near the notch tip and partial opening of the RSW specimens were discussed. With the range of loading speed and the joint configuration (overlap structure, nugget size, etc.) studied in this work, the plugging fracture should be a prevailing mode. The crack propagation of the corona bond and pre-crack of the RSW specimens under impact loading was found to affect the dynamic fracture process of the RSW specimens under bullet impact.

Measurement of High Strain Rate Indentation-Induced Deformations in Al<sub>2</sub>O<sub>3</sub>/SiC<sub>p</sub> Composite Ceramics

Al2O3/SiCp composite ceramics with 2 vol%, 5 vol% and 10 vol% SiC nanoparticles additions were hot pressed at 1650 °C. The polished ceramic discs were prepared and indented at high strain rate using a compressed gas gun with tiny tungsten carbide bullets. The microstructure and mechanical properties were obtained to explain the dynamic deformation behavior of Al2O3/SiCp ceramics. Cr3+ fluorescence mapping was used to examine the residual stress and plastic deformation induced on the surface of each target. The residual compressive stress area around the crater was evenly distributed, while the greatest plastic deformation was found at the hitting point of the bullet tip. It can be calculated that the high temperature of 1400K may be produced at the instant of the bullet impact and result in large plastic deformation region and low residual stress of the Al2O3/SiCp ceramic.

The Accuracy and Repeatability of Reconstructing Single Bullet Impacts Using the 2D Ellipse Method.

When a bullet punctures a surface, it leaves behind a bullet impact, which can be analyzed in order to determine the origin and trajectory path from which a bullet was discharged using many different scientific methods to reconstruct a shooting scene. The purpose of the research was to test the accuracy and repeatability of reconstructing the impact angle of single bullet impacts using the ellipse method. The research was conducted by firing various calibers of ammunition into drywall panels positioned at varying angles of incidence from 88° until ricochet occurred. This was done in order to determine which caliber type and angle of incidence are most accurate and precise for reconstructing a shooting scene. The study examined four caliber types fired into drywall panels, with 5 repeated shots for each of the 11 angles of incidence (n=220). Furthermore, 31 participants partook in the study to estimate a bullet impact angle of incidence utilizing the ellipse method. The results show that the best performance (accuracy and repeatability) is seen with the measurements of the 0.45 caliber ammunition. When angle of incidences is low (<64°), the performance (accuracy and repeatability) was seen to be better in all caliber ammunitions. Overall, the data provided for single bullet impacts deposited in drywall show that the ellipse method is useful in providing measurements for most crime scene reconstruction purposes and has also demonstrated that results vary depending on the type of ammunition, firearm, and angle of incidence being examined.

Ballistic Limit Estimation Approaches for Ballistic Resistance Assessment

The armour technologist conducts ballistic impact testing either for evaluating armour materials and systems or for studying material’s defeating mechanism. Most standards make use of the ballistic limit velocity for ballistic assessment. This is the bullet impact velocity that leads to the protection perforation in 50 per cent of the cases. Various models have been emerged to estimate this key metric. The present article summarises the popular models developed for ballistic limit estimation. An attempt is made to point out models’ strength and weakness. First, the experimental set-up used for that goal is displayed. Next, a concise overview of ballistic limit estimation methods is presented. Lastly, a discussion is dedicated to model’s comparison and analysis. This literature survey reveals that the main drawback of already existing methods is that they are purely statistical. Moreover, existing methods are based on the normality assumption of perforation velocities which tends from -infinity to infinity. The main conclusion of this survey is that the presented methods offer a comparable accuracy in estimating the ballistic limit velocity. However, a given variability is remarked when extreme values estimation is of interest, impact velocities leading to low and high perforation probability. Finally, existing models’ performances decay with the reduction of the experimental sample size which represent a constraining requirement in ballistic resistance assessment.

Numerical simulation of bolted joint composite laminates under low-velocity impact

In the present study, a three-dimensional finite element model of the bullet impact composite laminates is proposed. The user material subroutine VUMAT is used in the proposed three-dimensional model. The failure of composite laminates under different impact energies is analyzed, and the progressive failure process of the composite laminates is further analyzed to predict the failure strength of composite laminates. Then, based on this method, a three-dimensional finite element model of bolted joint composite laminates under low-velocity impact is established. The effects of bullet impact on the bolted joint composite laminates under different boundary conditions are analyzed, and the failure characteristics of the composite structures are investigated when the bullets impacted different positions.

Bullet Impact Detection in Silhouettes Using Mask R-CNN

The bullet impact detection in the silhouette plays an important role in the institutions which have a shooting range, specially where are regulated the license to carry a gun and where the evaluation manual process could present distortion in the ability’s evaluation of the shooter and like a consequence the license’s issuance. This paper proposes a method for an automatic detection of the bullet impacts in silhouettes based on deep learning and image processing, which consist of the following steps: pre-processing, impacts detection, edge detection and evaluation results. The experiments about 600 silhouettes with 2401 bullet impacts images of the proposed and implemented method considering the models Resnet 50 and Resnet 101 for Mask R-CNN show that Resnet 50 get better results than Resnet 101, achieving 97.6 %, 99.5 %, and 97.9 %, of accuracy, precision and recall, respectively, above the methods Circular Hough Transform, Circlet Detection, Random Sample Consensus, Randomized Hough Transform, Randomized Circle Detection, Support Vector Machine, Faster R-CNN, MnasNet and YOLO. Also, the results show 100 % of effectiveness in the edge detection and the count of the detected bullet impacts.