Bullet Impact Research Articles

Behavior of bamboo wall panel under bullet impact load

Bamboo mesh plastered with mud was a popular walling material across the world. About 100 years ago, this system was modified by applying mortar in place of mud, revising the Ekra wall system. The houses usually have wooden battens with bamboo mesh plastered with mortar usually called an Assam type house. This technology has become common in the north-eastern part of India and now it is rapidly going towards extinction in modern-day construction. This paper presents the efforts to find out the energy absorption by Bamcrete wall panels compared to the RCC panel under bullet impact load. Three different types of panels i.e. single, twin mesh Bamcrete and RCC panel were constructed. Two types of bullet SLR 7.62 mm and INSAS 5.56 mm were used in this study. The study showed that the twin mesh Bamcrete panel absorb higher energy as compared to RCC panel.

Impact protection of borosilicate glass plates with elastomeric coatings in drop tower tests

Drop tower testing was performed on borosilicate glass plates to determine the effectiveness of an elastomeric polyurethane/urea coating against impact and to improve our understanding of how the coating could be used to protect high voltage (HV) porcelain bushings against rifle damage [1,2]. Drop tower testing was found to be a very useful and practical tool for the prediction of failures of very brittle materials subjected to low energy impact as a function of coating thickness. The testing also improved our understanding of the impact behavior of the coatings and how to relate their low energy impact performance in drop tower tests to much higher energy impact situations, such as rifle bullet impact. By performing a series of drop tower tests on the plates with the coating thickness ranging from 1.3 to 5.6 mm, the effectiveness of the coating was determined from the critical contact force and from the critical impulse. These critical parameters were determined at the onset of catastrophic fractures of the uncoated and coated glass specimens. It was found that the coating protected the glass samples by a factor of 5.25 times with respect to the critical maximum contact force, and 9.31 times with respect to the critical impulse. Therefore, the overall coating effectiveness was estimated to be 7.28. It was also shown that the high effectiveness of the elastomeric coating can be achieved for a coating thickness as small as 1.3 mm, for a range of critical impact energies between 8.7 J and 22.7 J. Since the same coating with a thickness of 3 mm efficiently protected HV porcelain bushings against rifle impact at energies as high as 3.1 kJ [2], the very high effectiveness of the protection for small coating thicknesses could be independent of the impact energy within the range of energies considered. This therefore could be the main observation from the comprehensive work performed in this study and in [1,2].

Numerical modelling of crack initiation, propagation and branching under dynamic loading

In this paper crack initiation, propagation and branching phenomena are simulated using the Pseudo-Spring Smoothed Particle Hydrodynamics (SPH) in two and three-dimensional domains. The pseudo-spring analogy is used to model material damage. Here, the interaction of particles is limited to its initial immediate neighbours. The particles are connected via springs. These springs do not provide any extra stiffness in the system but only define the level of interaction between the connecting pairs. It is assumed that a crack has passed through a spring connecting a particle pair if the damage indicator of that spring becomes more than a predefined value. The crack branching of a pre-notched plate under dynamic loading and the effect of loading amplitude are studied. The computed crack speeds, crack paths and surfaces are compared with experimental and numerical results available in the literature and are found to be in good agreement. Next, the effect of notch location for a plate with a circular hole is studied. The ability of the framework to model arbitrary crack paths and surfaces are also demonstrated via three-dimensional simulations of chalk under torsion, Kalthoff-Winkler experiment, Taylor bullet impact and crack branching.

Influence of key design parameters of ultra-high performance fibre reinforced concrete on in-service bullet resistance

This study investigates the influence of key parameters on in-service bullet impact resistance of ultra-high performance fibre reinforced concrete (UHPFRC), with the aim to provide design guidance for the engineering applications. The effects of steel fibre type and dosage, matrix strength, coarse basalt aggregates, and target thickness are researched by subjecting the UHPFRC to a 7.62 mm bullet shooting with velocities of 843–926 m/s. The results show that the UHPFRC, designed by using a particle packing model with compressive strength around 150 MPa, is appropriate to develop protective elements considering both anti-penetration performance and cost-efficiency. The 13 mm short straight steel fibres show better anti-penetration than the 30 mm hook-ended ones, and the optimum volume dosage is approximately 2% by considering both the penetration and crack inhibition. Introducing coarse basalt aggregates with the particle size up to 25 mm into UHPFRC reduces the powder consumption from 900 kg/m3 to 700 kg/m3, and results in slightly higher mechanical strength and significantly enhanced bullet impact resistance with 14.5% reduction of penetration depth. The safe thicknesses (perforation limit) of the designed UHPFRC slabs are approximately 85 mm and 95 mm to withstand the 7.62 × 51 mm NATO armor-piercing bullet impact under velocity 843 mm/s and 926 mm/s, respectively.

Ramie, Cotton, and Rayon Double Ply Combination Composite for Bullet Proof Vests Body Armor

The bullet proof vest from composite fiber double ply from combination of ramie, cotton, and rayon, have been studied in order to improve the bullet proof vest in previous research using composite of pure ramie fiber. The mechanical bonding of the composite reinforced natural fiber can be increased by using chemical treatment of fiber or by using the addition of coupling agent. The chemical treatment, for example alkali treatment, is often used because it is more cost-effective. By increasing mechanical bonding also increasing the tensile strength of the composite so that this material could restrain the impact of the bullet. The result shows that the tensile strength of the composites have the optimum values for 30 minutes treated fiber in a 5% NaOH solution, i.e. 13.31 MPa, the tensile test specimens were produced according to ASTM D-638. This research is to investigate the ability of the double ply fabric itself from the bullet impact, the fiber composite and also the combination of fiber composite as a front layer (Panel A) and the double ply fiber as a second layer (Panel B) for a bullet proof vest. Optimal combination is obtained with 5 layers of panel A and 20 layers of panel B which is able to protect against cal. 7.65 mm × 17 mm (.32 ACP) bullet fired through .32 Pindad pistol from a distance of 10 meters. Panel with a size of 20 cm × 20 cm has a total thickness of 14.69 mm and a total weight of 454.73 gram. Scanning electron microscopy (SEM) observations indicated that the porosity and surface area of the fiber is smooth, fiber surfaces showed topography with microporous. SEM also showed well-arranged structure of fibers bonding. Energy Dispersive X-ray (EDX) analysis indicated 99,6% carbon contents in ramie-cotton-rayon fiber. Test result indicates that panel from composite ramie-cotton-rayon-epoxide can reach the level 1 of International Standard of NIJ-010104. Compared to panel from pure ramie fiber, the panel from this composite (0.454 kg) is lighter than previous research (0.52 kg). This combination can restrain the bullet from 10 meters distance, shorter than the previous research in 20 meters distance.

Experimental measurement of the bullet trajectory after perforation of a chambered window

AbstractThe assessment of the failure and final response for glass structures loaded by high‐speed events such as blast or projectile loading are challenging tasks for researchers. For many studies, knowledge about the strain rate effect in brittle materials and well described finite element simulations are not enough to reach a correct outcome. For that reason, only experimental assessments can give credible results. Moreover, the impacting glass fragments or projectiles often change the angle of the trajectory after perforation of a target. In this study, the authors present the change in the 3000 J military bullet trajectory after total penetration of a two‐chambered civil engineering facade window. A series of actual tests were performed for different angles of the soda‐lime float glass specimen that were subjected to bullet impact. The results obtained chambered windows given an understanding of the behavior of the separate glass surfaces under such complex scenarios. Furthermore, the presented tests support the designers and military shooters by the assessment methodology of projectile bullet trajectory change as a function of the incident angle.

Concrete slab fragmentation after bullet impact: An experimental study

The response of nonreinforced concrete to high-speed flying fragments depends on many factors such as composition, geometry and boundary conditions of the obstacle. In this study, the authors verified experimentally a series of concrete slabs with various aggregate types and amounts of steel reinforcement. The material properties were previously developed and verified during the laboratory experiments with standard cubic specimens. Moreover, the main goal of this research was the verification of high-strength concrete plates using different kinds of aggregate, that is, traditional gravel, granite, basalt and amphibolite subjected to the military bullet impact. It is known that the aggregate filled about 70% of total concrete volume, and therefore, the properties of aggregate, like density, strength and surface will be the main factors influencing the concrete strength and further concrete resistance to projectiles. The research presented shows that the type and shape of aggregate determined the conditions of concrete failure. The outcomes show that the obtained compressive strength varied between 60 and 80 MPa. In the second stage of the test, randomly distributed reinforcement was added to selected concrete mixtures. Hooked steel fibres with an aspect ratio of 50 in the amounts of 50 and 100 kg per cubic metre were applied. The influence of steel fibres on the concrete properties was verified in compressive and splitting strength tests. On the basis of preliminary laboratory tests, the final slab specimens, with the dimensions of 0.5 × 0.5 m and 0.05 m thickness, were produced. The final verification was performed in the real field conditions using the most popular military bullet, whose kinetic energy was more than 2000 J. The measurements of the initial and final velocities of the bullets and concrete fragments were obtained using high-speed camera measurement equipment. The final failure of the slabs was presented as the primary outcome.

Estimation of the Propagation of the Impact Wave Phenomenon as a Result of a Bullet Impact in PACVD-Modified Textiles

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Heterogeneous lightweight configuration for protection against 7.62 × 39 mm bullet impact

Configuration of a heterogeneous lightweight material is investigated numerically and experimentally, for protection against 7.62 × 39 mm mild steel core bullet impact. The configuration consists of alumina (Al2O3) tile followed by fiber glass and polyurethane foam, all covered with kev-epoxy layer. Numerical simulations were performed using ANSYS AUTODYN. The 10-mm thick alumina completely disrupts the impacting bullet through blunting and erosion. The fiber glass and polyurethane foam disperse and absorb the propagation of shock wave, respectively. The kev-epoxy cladding seizes any scattering of brittle alumina fragments. The average impact velocity of the bullet was measured to be 710 m/s using high-speed camera. A 10-mm depth of depression spread over a wider area of 3.92 sq in of torso was recorded in blunt force trauma test, which was well within the European, German, and British standards that allow a 20–25 mm backface signature. Due to these characteristics it can be employed as body armor, vehicle armor, and for the safety and security of other critical infrastructures against this bullet and fragment impact. The residual mushroom-shaped bullet and its length of 9.3 mm in numerical simulation is in close agreement with the measured value of the 8.0 mm recovered bullet size and shape.

Damage prevention in transformer bushings subjected to high-velocity impact

This paper contributes further to the discussion recently initiated in Ref. [1] regarding the protection of pressurized porcelain bushings against high-velocity impacts on high-voltage (HV) transformers by means of an elastomeric coating. Valuable observations and conclusions were made in our previous work concerning the impact behavior of the bushings and their protection from a unique combination of ballistic air gun tests performed on borosilicate glass cylinders, representing the bushings, and from flat glass plates tested via drop tower. Clearly, the conclusions from our previous work, critical to many utilities world-wide, needed to be independently verified by full-scale ballistic testing performed on the actual bushings under rifle bullet impact. In addition, to complete the impact analysis, the coated borosilicate cylinders were subjected to impact at energies higher than an air gun to demonstrate the energy effect on cylinder failure. Also, the cascading failures of the cylinders was investigated in this work, for the first time, to show what a single unprotected bushing failure could do to surrounding infrastructure. It was shown that the cascading failure of pressurized unprotected bushings could be a real and dangerous threat in a substation. It was also found that the linear extrapolations of fragmentation behavior with respect to energy in [1] is misleading. Most importantly, the unique but slightly speculative predictions of coating protections on the bushings were significantly overestimated, which was clearly demonstrated in this work. The bushings could be protected by an elastomeric coating against rifle bullet impacts with a coating thickness of a few mm instead of 60 mm as previously reported.

On the Dynamic Response of Laminated Glass Exposed to Impact Before Blast Loading

In this study, the effect of fragment or bullet impact before blast loading on laminated glass is studied experimentally. First, laminated windows consisting of two 3.8 mm thick annealed float glass plates and a 1.52 mm thick PVB interlayer were blast loaded in a shock tube with various pressures as a reference. In these tests, the blast loading was successively increased until fracture occurred not only in the glass plates but also in the PVB interlayer. Second, a diamond drill was used to make a 5 mm diameter centrally placed hole in some windows before they were blast loaded with the same pressures as those used for the undamaged windows. Third, windows were impacted by 7.62 mm AP bullets, both with and without the brass jacket, before they were blast loaded. Such bullets may have similar mass and velocity to typical primary fragments from an explosive detonation. The results are finally compared with each other and discussed with respect to the blast protection offered. It is found that the capacity is significantly reduced if the laminated glass is perforated by a fragment or a bullet before it is blast loaded and that such impacts should be considered in the design of blast-resistant windows.

Defining animal welfare standards in hunting: body mass determines thresholds for incapacitation time and flight distance

Shooting is an important tool for managing terrestrial wildlife populations worldwide. To date, however, there has been few quantitative methods available enabling assessment of the animal welfare outcomes of rifle hunting. We apply a variety of factors to model flight distance (distance travelled by an animal after bullet impact) and incapacitation from the moment of bullet impact. These factors include body mass, allometric and isometric scaling, comparative physiology, wound ballistics and linear kinematics. This approach provides for the first time a method for quantifying and grading the quality of shooting processes by examining only body mass and flight distance. Our model is a universally applicable tool for measuring animal welfare outcomes of shooting regimes both within and among species. For management agencies the model should be a practical tool for monitoring and evaluating animal welfare outcomes regarding shooting of mammalian populations.

Contamination, Fate and Management of Metals in Shooting Range Soils—a Review

Pollution of shooting range soils by lead from bullets represents a widespread and potentially significant concern for impact on the environment. High concentrations of lead in particular are reported in bullet impact berms and shot fall zones. The other components of bullets used in shooting including antimony, copper and zinc may also be present at elevated concentrations. Antimony is a concern due to its mobility in the environment. It has been recognised that the status of contamination is important for the risk presented by shooting ranges. Lead bullets are subject to weathering in the soil, forming secondary minerals, which may be solubilised and may release lead and co-contaminants into the soil. The mobility and availability of contaminants in the soil affect their potential for spreading in the environment and for uptake and toxicity in organisms. Soil physicochemical properties affect bullet weathering and availability of contaminants in the soil. A number of strategies have been researched for management of shooting range pollution such as chemical stabilisation, phytoremediation and soil washing. This review considers the current state of knowledge and research of contamination and management of shooting ranges from recent literature (2014–2017) reflecting on new knowledge and novel management strategies for shooting range soil management. Ultimately, management of pollution in shooting range soils should seek to remove bullets from soil, reduce the weathering of bullets and reduce the mobility and bioavailability of contaminants. Adopted management practices should be based an understanding of site-specific condition, to achieve the most optimal outcome.

Poisson effect enhances compression force sensing with oxidized carbon nanotube network/polyurethane sensor

Poisson effect when a sensor made of multi-walled carbon nanotube network embedded in the elastic polyurethane was compressed in one direction and expanded in the other two directions perpendicular to the direction of compression several fold enhanced the sensing owing to nano-sized cracks of the network. The composite sensitivity was further multiplicatively enhanced by KMnO4 oxidation of carbon nanotubes. As an example of the composite use as a compression sensor, a pressure on the shoe sole was monitored as well as a ball bullet impact on the sensor.

Failure mechanism of resistance-spot-welded specimens impacted on base material by bullets

The tests of bullet impact on the base material (BM) of a simple specimen with a single resistance-spot-welded (RSW) nugget of TRIP800 steel are performed to investigate the response of the RSW specimen to the ballistic debris impact on the RSW specimen. A one-stage gas gun is used to fire the bullets while a laser velocity interferometer system for any reflector (VISAR) is used to measure the velocity histories of the free surfaces of the RSW specimen. The recovered RSW specimens are examined with the three-dimensional super depth digital microscope (SDDM) and the scanning electro microscope (SEM). For the tests of small multiple-bullet impact, it is revealed that the wave train of the VISAR measured results and the detachment of the base material interfaces in the recovered RSW specimens are directly related to the reflection and refraction of the curved stress waves incoming to the interfaces and the free surfaces in the RSW specimens. The detachment of BM interfaces can lead to the impact failure of the RSW joints for the larger multiple-bullet impact at higher velocity, the mechanism of which is different from the case for normal incidence (spalling). For the tests of single large bullet impact, it is brought to light experimentally that the plastic strain concentration at the “notch tip” spurs either the crack near the RSW joint or the split of the nugget. The numerical simulation shows up the process of splitting the nugget: a crack initiates at the “notch tip”, propagates across the nugget interface and splits the nugget into two parts. It is indicated that the interaction between the stress waves and many interfaces/free surfaces in the RSW specimen under ballistic impact causes variable local stress triaxialities and stress Lode angles, which affects the deformation and fracture mechanism of the RSW specimen including stretching and shearing failure. It is shown that the impact failure of the RSW joints is a mixture of brittle fracture and ductile fracture while the fracture or perforation of the BM is ductile.

Rock Dynamic Fracture Characteristics Based on NSCB Impact Method

In 2012, the International Society for Rock Mechanics (ISRM) recommended a new Notched Semicircular Bend (NSCB) method for the determination of dynamic fracture toughness of rock materials, but it did not consider the effect of some uncontrollable factors in the course of the experiment on the test result. This thesis firstly carried out dynamic fracture toughness experiments on several typical rock materials such as sandstone using the modified Split‐Hopkinson Pressure Bar (SHPB) experimental system with high‐speed photography, directly compared the dynamic fracture failure characteristics of several rock materials, and examined the loading rate dependency of the dynamic fracture toughness of rock materials. Based on the numerical analysis method of Discrete Lattice Spring Model (DLSM), it focused on the effect of bullet impact loading rate, loading area of incident bar, support restraints of clamping specimen, and other uncontrollable factors in the course of SHPB experiment on test results. The findings can be referenced for the improvement of NSCB method.

Multi-Scale Modeling of Composites with Surrogate and Uncertainty in Residual Velocity for High-Speed Impacts

The bullet impact onto a composite plate has been investigated both numerically and experimentally. The main purpose is to numerically identify the range of uncertainty shown in the residual velocities from the high-speed impact test data. The simulation is based on the multi-scale modeling for composites. The experimental results presented here include the tensile tests of composite specimen to identify the range of failure strains and mainly the ballistic shot test onto a laminated plate to measure the residual velocities with especial interests in the range of uncertainty. All test data have been compared with numerical predictions and the scattered test data are reasonably well captured with simulations.

Large area imaging of forensic evidence with MA-XRF

This study introduces the use of macroscopic X-ray fluorescence (MA-XRF) for the detection, classification and imaging of forensic traces over large object areas such as entire pieces of clothing and wall paneling. MA-XRF was sufficiently sensitive and selective to detect human biological traces like blood, semen, saliva, sweat and urine on fabric on the basis of Fe, Zn, K, Cl and Ca elemental signatures. With MA-XRF a new chemical contrast is introduced for human stain detection and this can provide a valuable alternative when the evidence item is challenging for conventional techniques. MA-XRF was also successfully employed for the chemical imaging and classification of gunshot residues (GSR). The full and non-invasive elemental mapping (Pb, Ba, Sr, K and Cl) of intact pieces of clothing allows for a detailed shooting incident reconstruction linking firearms and ammunition to point of impact and providing information on the shooting angle. In high resolution mode MA-XRF can even be used to provide information on the shooting order of different ammunition types. Finally, by using the surface penetration of X-rays we demonstrate that the lead signature of a bullet impact can be easily detected even if covered by multiple layers of wall paint or human blood.

Synthesis of technical protective textile

Every type of clothing provide us protection to some extent. Our focus is not concern with clothes(fabrics) who protect us from winter, rain or heat but on the synthesis of protective textile, briefly describing the design of specialized fabric to provide protection from fire, chemicals, nuclear radiations, bullet impact etc. Extensive research is being done to develop the protective clothing for various regular and specialized civilian and military people. The global growth rates of technical textiles are about 4% per year, greater than the growth of home and apparel textiles, which are growing at a rate of 1% per year. The main target of the technical protective fabrics is to improve people safety in their work place. Technical protective fabrics are made up of different kind of fibers, because every blend contains different technical characteristics.

Performance of natural curaua fiber-reinforced polyester composites under 7.62 mm bullet impact as a stand-alone ballistic armor

A multilayered armor system (MAS) is intended to personal protection against high kinetic energy ammunition. MAS layers are composed of materials such as a front ceramic and a back composite that must show both high impact resistance and low weight, usually conflicting characteristics. Synthetic fiber fabrics, such as Kevlar™ and Dyneema™, are the favorite materials to back the front ceramic, due to their high strength, high modulus and relatively low weight. Recently, composites reinforced with natural fibers have been considered as MAS second layer owing to their good performance associated with other advantages as being cheaper and environmentally friendly. Among the natural fibers, those extracted from the leaves of the Ananas erectifolius plant, known as curaua, stand out due to its exceptional high strength and high modulus. Thus, the objective of the present work is to evaluate the performance of curaua fiber-reinforced polyester composites subjected to ballistic impact of high energy 7.62mm ammunition. Composites reinforced with 0, 10, 20 and 30vol.% of curaua fibers were produced and stand-alone tested as armor target to evaluate the absorbed energy. Analysis of variance (Anova) and Tukey's honest significant difference test (HSD) made it possible to compare the results to Kevlar™ laminates. Among the tested materials, the 30vol.% fiber composites were found to be the best alternative to Kevlar™.