Fragment Simulating Projectile Research Articles

Studying the strengthening mechanism and thickness effect of elastomer coating on the ballistic-resistance of the polyurea-coated steel plate

Experiments have shown that the ballistic performance of the steel plate improves significantly after coating polyurea at the impact face. However, the strengthening mechanism of the elastomer coating on the ballistic-resistance is not understood well until now. In this paper, the strengthening mechanism and thickness effect of the coating under fragment simulating projectiles (FSP) impact are studied through numerical and experimental analysis. Firstly, a viscoplastic constitutive model of polyurea is developed based on experimental characterization and thermodynamic equation of state. It can capture strongly nonlinear volumetric behavior and impact-induced shearing stiffening and strengthening considering the coupling of high pressure, high temperature, and high strain rate under ballistic impact. Then, by applying this newly developed viscoplastic model of polyurea, the underlying ballistic-resistant mechanism of the polyurea-coated steel plate is numerically studied. The analysis shows that the dynamic behavior of polyurea under ballistic impact and propagating regulation of impact wave jointly play the key role. One side, the impact-induced stiffening and strengthening of the polyurea change the failure modes of the steel plate and considerably improve the ballistic-resistance of the structure. The other side, increasing coating thickness can only provide the limited benefit for improving the ballistic-resistance of the structure, as obtained in experiments. For the impact-face-coated steel plate, the low-thickness polyurea coating suffering from FSP impact can increase the frequency of the compressive wave reflection-superposition on the high-impedance polyurea/steel interface before the energy transfer from the impacted location. This helps to improve the pressure level and enhance the instantaneous energy storage and dissipation of the polyurea per volume significantly. However, increasing coating thickness can make the pressure level and the specific energy density of polyurea decrease gradually during penetration. It is also found that the energy dissipation of FSP during penetration is reduced after increasing the coating thickness because of the erosion mitigation from the structure. The new insight on the strengthening mechanism of elastomer coating will be helpful for the light armor design.

Predicting metallic armour performance when impacted by fragment-simulating projectiles – Model adjustments and improvements

In a previous study, a set of nine existing penetration models for blunt projectiles were identified and reviewed for their ability to predict the plugging-mode ballistic limit velocity of monolithic titanium alloy, aluminium alloy, and steel plates. Assessed with a database of more than 650 experimental ballistic limit measurements, often at conditions beyond that for which they had been originally derived or validated, it was found that all nine models could predict the ballistic limit to within +/- 50% for more than 50% of the database entries. In this paper, simple modifications to these nine models are proposed that introduce empirical adjustments, reformulations of the target strength dependency, or a combination of both with the pragmatic goal of identifying a model suitable for application across the wide range of monolithic metallic targets impacted by different calibre fragment-simulating projectiles across a full range of ordnance and sub-ordnance velocities in our database. The modifications were able to improve the performance of all models across this range, with the best performing models able to predict the experimental ballistic limit to within +/- 10% for 50% of the database entries and to within +/- 20% for 76% of the database entries.

Predicting metallic armour performance when impacted by fragment-simulating projectiles – model review and assessment

Metallic targets impacted by blunt-nosed, fragment-simulating projectiles typically fail via shear plugging. A number of models exist in open literature to predict the onset of this failure mode, which can be used to determine the ballistic limit velocity, VBL, for a particular combination of projectile and target plate. A set of nine existing penetration models for blunt projectiles were identified and reviewed for their ability to predict the plugging-mode ballistic limit velocity of monolithic titanium alloy, aluminium alloy, and steel alloy plates impacted by blunt-nosed, fragment simulating projectiles. A database of more than 650 experimental ballistic limit measurements was used to evaluate the performance of the predictive models, covering a wide range of ordnance and sub-ordnance velocities, normal and oblique impact angles, and target plate thicknesses. The range of experimental data typically exceeded that for which the applied models were derived or previously validated. Nonetheless, it was found that all nine models could predict the experimental ballistic limit to within +/- 50% of the experimental measurement for more than 50% of the ballistic tests considered.

A filament-level analysis on failure mechanism and ballistic limit of real-size multi-layer 2D woven fabrics under FSP impact

This paper investigates the failure mechanism and fabric ballistic performance of real-size multi-layer 2D woven fabrics impacted by sharp-edge fragment simulating projectile (FSP). First, the relations between digital fiber shear force and bending rigidity are established under the modified digital element approach (DEA) framework. Then, a systematic parametric study was carried out on the ballistic impact of a 4-inch-long single yarn and 4-inch by 4-inch 2D woven fabric at near fiber level to solve for the relations of digital fiber moment of inertia and ballistic limit. The results show that for the same number of digital fibers per yarn model, the simulated ballistic limits are in direct proportion to digital fiber moment of inertia. The increase of the number of digital fibers per yarn, however, decreases the digital fiber moment of inertia effect on ballistic limits. Second, the 1- to 28-layer real-size 2D woven Kevlar KM2 fabrics are simulated at filament level against FSP on the cluster to estimate the V50 zone. The perforation process and failure mechanism of 4-layer fabric is investigated and analyzed in detail. The simulation results demonstrate the deformed fabric shape with respect to time and the damage modes at the impact area. Numerical results are compared with standard ballistic test results.

Ballistic protection performance of a free ceramic particle armor system: An experimental investigation

In this work, the ballistic protection performance of a free ceramic particle armor (FCPA) system was experimentally investigated. The armor system was designed by free ceramic balls in between two outer plates.9 × 19 mm Parabellum pistol cartridges and 0.3 caliber fragment-simulating projectiles (FSP) were used to investigate effects of armor thickness on the ballistic performance. The observed results showed that the designed free ceramic particle armor system is a promising candidate for ballistic protection applications in terms of high strength-to-weight ratio, excellent energy absorption, and mechanical properties.

Experimental Investigation of Transverse Loading Behavior of Ultra-High Molecular Weight Polyethylene Yarns

Ultra-high molecular weight polyethylene (UHMWPE) Dyneema® SK-76 fibers are widely used in personnel protection systems. Transverse ballistic impact onto these fibers results in complex multiaxial deformation modes such as axial tension, axial compression, transverse compression, and transverse shear. Previous experimental studies on single fibers have shown a degradation of tensile failure strain due to the presence of such multi-axial deformation modes. In this work, we study the presence and effects of such multi-axial stress-states on Dyneema® SK-76 yarns via transverse loading experiments. Quasi-static transverse loading experiments are conducted on Dyneema® SK-76 single yarn at different starting angles (5°, 10°, 15°, and 25°) and via four different indenter geometries: round (radius of curvature (ROC) = 3.8 mm), 200-micron, 20-micron, and razor blade (ROC ~2 micron). Additionally, transverse loading experiments were also conducted for a 0.30 cal. fragment simulating projectile (FSP) and compared to other indenters. Experimental results show that for the round, 200-micron indenter, and FSP geometry the yarn fails in tension with no degradation in axial failure strain compared to the uniaxial tensile failure strain of SK-76 yarn (2.58%). Whereas for the 20-micron indenter and razor blade, fibers fail progressively in transverse shear followed by progressive strength degradation of the yarn. Strength degradation of yarn occurs at relatively low strains of 0.6–0.7% with eventual failure of the yarn at approximately ~1.8% and ~1.5% strain for the 20-micron indenter and razor blade, respectively. Breaking angles (range of 10°–30°) are observed to have little effect on the failure strain for all indenter geometries.

An Experimental Study on Ballistic Limit of Aluminum Plate Subjected to Fragment-Simulating Projectile

The ballistic limit of the aluminum plate was investigated in this study. There were two conditions of plate which were single and double plate. The double plates were categorized into two sections which were separated 100 mm to each other. The first category had nothing in between two plates, but for the second category, there was fluid in between plates. Those plates were impacted by the fragment-simulating projectile (FSP) at various velocities. The velocity of the FSP was varied by changing the charge weight inside the bullet’s jacket. The experiment was conducted at Science Technology Research Institute for Defence (STRIDE), Batu Arang, Selangor. As far as the result was concerned, the ballistic limit was observed to be greatly affected by the arrangement of the plate.

Mapping the Risk of Fracture of the Tibia From Penetrating Fragments.

Penetrating injuries are commonly inflicted in attacks with explosive devices. The extremities, and especially the leg, are the most commonly affected body areas, presenting high risk of infection, slow recovery, and threat of amputation. The aim of this study was to quantify the risk of fracture to the anteromedial, posterior, and lateral aspects of the tibia from a metal fragment-simulating projectile (FSP). A gas gun system and a 0.78-g cylindrical FSP were employed to perform tests on an ovine tibia model. The results from the animal study were subsequently scaled to obtain fracture-risk curves for the human tibia using the cortical thickness ratio. The thickness of the surrounding soft tissue was also taken into account when assessing fracture risk. The lateral cortex of the tibia was found to be most susceptible to fracture, whose impact velocity at 50% risk of EF1+, EF2+, EF3+, and EF4+ fracture types – according to the modified Winquist-Hansen classification – were 174, 190, 212, and 282 m/s, respectively. The findings of this study will be used to increase the fidelity of predictive models of projectile penetration.

Study of high-speed-impact-induced conoidal fracture of Ti alloy layer in composite armor plate composed of Ti- and Al-alloy layers

In order to understand the mechanism of conoidal fracture damage caused by a high-speed fragment-simulating projectile in titanium alloy layer of a composite armor plate composed of titanium- and aluminum-alloy layers, the ballistic interaction process was successfully simulated based on the Tuler–Butcher and GISSMO coupling failure model. The simulated conoidal fracture morphology was in good agreement with the three-dimensional industrial-computed-tomography image. Further, three main damage zones (zones I, II, and III) were identified besides the crater area, which are located respectively near the crater area, at the back of the target plate, and directly below the crater area. Under the high-speed-impact conditions, in zone II, cracks began to form at the end of the period of crack formation in zone I, but crack formation in zone III started before the end of crack formation in zone II. Further, the damage mechanism differed for different stress states. The microcracks in zone I were formed both by void connection and shear deformation. In the formation of zone I, the stress triaxiality ranged from −2.0 to −1.0, and the shear failure mechanism played a dominant role. The microcracks in zone II showed the combined features of shear deformation and void connection, and during the formation process, the stress triaxiality was between 0 and 0.5 with a mixed failure mode. Further, the microcracks in zone III showed obvious characteristics of void connection caused by local melting. During the zone III formation, the triaxiality was 1.0–1.9, and the ductile fracture mechanism was dominant, which also reflects the phenomenon of spallation.

Gelatine Backing Affects the Performance of Single-Layer Ballistic-Resistant Materials Against Blast Fragments.

Penetrating trauma by energized fragments is the most common injury from explosive devices, the main threat in the contemporary battlefield. Such devices produce projectiles dependent upon their design, including preformed fragments, casings, glass, or stones; these are subsequently energized to high velocities and cause serious injuries to the body. Current body armor focuses on the essential coverage, which is mainly the thoracic and abdominal area, and can be heavy and cumbersome. In addition, there may be coverage gaps that can benefit from the additional protection provided by one or more layers of lightweight ballistic fabrics. This study assessed the performance of single layers of commercially available ballistic protective fabrics such as Kevlar®, Twaron®, and Dyneema®, in both woven and knitted configurations. Experiments were carried out using a custom-built gas-gun system, with a 0.78-g cylindrical steel fragment simulating projectile (FSP) as the impactor, and ballistic gelatine as the backing material. FSP velocity at 50% risk of material perforation, gelatine penetration, and high-risk wounding to soft tissue, as well as the depth of penetration (DoP) against impact velocity and the normalized energy absorption were used as metrics to rank the performance of the materials tested. Additional tests were performed to investigate the effect of not including a soft-tissue simulant backing material on the performance of the fabrics. The results show that a thin layer of ballistic material may offer meaningful protection against the penetration of this FSP. Additionally, it is essential to ensure a biofidelic boundary condition as the protective efficacy of fabrics was markedly altered by a gelatine backing.

Ballistic penetration damages and energy absorptions of stacked cross-plied composite fabrics and laminated panels

Flexible fabrics have been widely used in body armor designs. Here we report ballistic impact damage of stacked cross-plied composite fabric and cross-plied laminated panels. The ballistic impact behaviors of stacked cross-plied composite fabric and cross-plied laminated panel have been tested with fragment-simulating projectiles under the strike velocity 550–600 m/s to explore the influence of the layers combination of fabric target on ballistic impact. Two types of macroscopic anisotropy continua finite element models based on fabric targets structures are established to analyze the ballistic mechanism of stacked cross-plied composite fabric and cross-plied laminated panels. The impact damage morphologies and energy absorptions have also been compared between the tests and finite element analysis results. We have found the stacked fabric construction absorbed more energy than their counterpart cross-plied laminated panel, while the laminated panel shows better structural integrity and stability during ballistic penetration.

The ballistic performance of bone when impacted by fragments

Physical models are required to generate the underlying algorithms that populate computer simulations of the effects of explosive fragmenting devices. These models and simulations are used for understanding weapon performance, designing buildings and optimising personal protective equipment. Previous experimental work has investigated the performance of skin and muscle when subjected to fragmentation threats, but limited evidence exists for the performance of bone when impacted by fragments. In the current work, ballistic testing was conducted using two types of internationally recognised steel fragment simulating projectiles (FSPs): (i) 5.5 mm diameter (0.68 g) ball bearing (BBs) and (ii) 1.10 g chisel nosed (CN). These projectiles were fired at isolated swine ribs at impact velocities between 99 and 1265 m/s. Impact events were recorded using a high-speed camera. Selected specimens were analysed post-impact with plain x-radiographs and micro-CT scanning to determine damage to the bone architecture. Bones were perforated with a kinetic energy density (KED) as low as 0.14 J/mm2. Energy transfer to the bone was greater for the CN FSPs, resulting in increased bone damage and the production of secondary bone fragments. The manner in which the bones failed with faster velocity impacts (> 551 m/s; KED > 6.44 J/mm2) was analogous to the behaviour of a brittle material. Slower velocity impacts (< 323 m/s; KED < 1.49 J/mm2) showed a transition in failure mode with the bone displaying the properties of an elastic, plastic and brittle material at various points during the impact. The study gives critical insight into how bone behaves under these circumstances.

Ballistic Performance Evaluation of Aluminium Plate Impact by Fragment Simulating Projectile

The ballistic performance has drawn attention to researchers from a military background. They intend to provide solutions to ensure the soldiers in the front line of war do not kill in action. A casualty in war can lead to depression among soldiers and not to mention to their family as well. The aim of this work is to provide preliminary data for the ballistic limit velocity, VBL of the hydrodynamic ram study. The test was conducted at Science and Technology Research Institute (STRIDE), Batu Arang, Selangor which is under the Ministry of Defence (MINDEF) Malaysia. The gas gun and fragment simulating projectiles (FSP) were employed in this test. There were about 16 rounds of fire were shot with different velocities from 246 up to 373 m/s. The ballistic limit velocity was calculated by taking the average of an equal number of highest partial perforation and the lowest perforation velocities. It was found that the VBL was equal to 275.8 m/s. On top of that, there were two main failure modes observed i.e. partial penetration and complete penetration.

Preliminary study of fragment simulating projectile on epoxy-ramie composite

This research is a preliminary study to determine the feasibility of the ballistic test equipment using fragment-simulating projectiles (FSP) and the ability of the rami-epoxy composite against bullet penetration. Tests have been conducted in which FSP were fired at epoxy ramie composites. Ballistic test equiment was equipped with a chronograph and high speed camera. The composites were manufactured using manual hand lay-up compression moulding 60% volume fraction. Based on the high speed camera result shows that the FSP projectile when crashing into the specimen was not in perfect position (tilted) and the ramieepoxy composite was fail in 6, 9, and 12 layers.

Perforation of Aluminum Armor Plates with Fragment-Simulating Projectiles

Experiments with fragment-simulating projectiles (FSP) and aluminum plates are conducted to evaluate the performance of various aluminum alloys and plate thicknesses to resist perforation against fragments. Ballistic-limit velocity data for several aluminum alloys and plate thicknesses are presented in several US Army Research Laboratory (ARL) reports. In this study, we present additional ballistic-limit data for plates thinner than the plates reported by ARL. In addition, we present an equation that predicts the ballistic-limit velocity for fragment-simulating projectiles (FSP) that perforate aluminum armor plates. The ballistic-limit equation is presented in terms of dimensionless parameters so that the geometric and material problem scales are identified. Predictions and data from two different fragment-simulating projectiles and two different strength aluminum alloys show the range of plate thicknesses for reasonable model predictions.

Bioinspired composite segmented armour: Numerical simulations

Nature has evolved ingenious armour designs, like the flexible carapaces of armadillo and boxfish consisting of hexagonal segments connected by collagen fibres, that serve as bioinspiration for modern ballistic armours. Here, Finite element modelling (FEM) used to analyze the effect of scale geometry and other impact parameters on the ballistic protection provided by a bioinspired segmented ceramic armour. For this purpose, the impact of cylindrical fragment simulating projectiles (FSPs) onto alumina-epoxy non-overlapping scaled plates was simulated. Scale geometrical parameters (size, thickness and shape) and impact conditions (FSP diameter, speed, location) are varied and the amount of damage produced in the ceramic tiles and the final residual velocity of the FSP after the impact are evaluated. It is found that segmentation drastically reduces the size of the damaged area without significantly reducing the ballistic protection in centred impact, provided the tile size is kept over a critical value. Such critical tile size (∼20mm, inscribed diameter, for impacts at 650m/s) is independent of the scale thickness, but decreases with projectile speed, although never below the diameter of the projectile. Off-centred impacts reduce the ballistic protection and increase the damaged area, but this can be minimized with an appropriate tile shape. In this sense and in agreement with the natural hexagonal tiles of the boxfish and armadillo, hexagonal scales are found to be optimal, exhibiting a variation of ballistic protection—measured as reduction of projectile speed—with impact location under 12%. Design guidelines for the fabrication of segmented protection systems are proposed in the light of these numerical results.

Virtual ballistic impact testing of Kevlar soft armor: Predictive and validated finite element modeling of the V 0 - V 100 probabilistic penetration response

Abstract This works presents the first fully validated and predictive capability to model the V0-V100 probabilistic penetration response of a woven fabric using a yarn-level fabric finite element model. The V0-V100 curve describes the probability of complete fabric penetration as a function of projectile impact velocity. The exemplar case considered in this paper comprises of a single-layer, fully-clamped, plain-weave Kevlar fabric impacted at the center by a 17-gr, 0.22 cal FSP or fragment-simulating projectile. Each warp and fill yarn in the fabric is individually modeled using 3D finite elements and the virtual fabric microstructure is validated in detail against the experimental fabric microstructure. Material and testing sources of statistical variability including yarn strength and modulus, inter-yarn friction, precise projectile impact location, and projectile rotation are mapped into the finite element model. A series of impact simulations at varying projectile impact velocities is executed using LS-DYNA on the fabric models, with each model comprising unique mappings. The impact velocities together with the outcomes (penetration, non-penetration) are used to generate the numerical V0-V100 curve which is then validated against the experimental V0-V100 curve. The numerical Vi-Vr data (impact, residual velocities) is also validated against the experimental Vi-Vr data. For completeness, this paper also reports the experimental characterization data and its statistical analysis used for model input, viz. the Kevlar yarn tensile strengths, moduli, and inter-yarn friction, and the experimental ballistic test data used for model validation.

Validation of the modified digital element approach for simulating ballistic impact against fragment simulating projectile

A modified digital element approach (DEA) is applied to simulate fabric perforation process under ballistic impact. The previous version of the DEA is capable of simulating ballistic impact of textile fabric using rigid body spherical and cylindrical projectiles only. Fragment simulating projectile (FSP) and real bullets are not modeled. The subject of this research is to perform ballistic penetration process against projectile of arbitrary shape and validate the modified DEA. A fabric to solid body projectile contact search and contact force calculation algorithm is established. Ballistic impact of textile fabrics against spherical and cylindrical projectiles is performed using the previous DEA and the modified DEA separately. Numerical results are compared to the well published DEA results to investigate the fabric bullet resistant performance.

Kompozyt warstwowy zwiększający odporność samochodów patrolowych i interwencyjnych na atak improwizowanych ładunków wybuchowych (IED) od dołu

Model layered composites were made of polyester resin reinforced with layers of glass fibre and aramid fibre fabrics. The fabrics for the study were selected in a manner enabling the comparison of their ballistic resistance depending on the material type and density. Additionally, aluminium plates were used to produce the composites.The study examined the resistance of the model composites to 1.1 g fragment simulating projectile (FSP) penetration, their susceptibility to deformation caused by shock waves produced by pure TNT charges, and their resistance to the effects of detonation of model improvised explosive devices (IED) containing fragments in the form of bearing balls. The analysis and optimisation of the test results enabled the selection of a layer configuration combining the materials studied that has the lowest area density and that protects car bottom structures against perforation in the case of a detonation of a small improvised explosive device.

Modeling and Experiments on Ballistic Impact into UHMWPE Yarns Using Flat and Saddle-Nosed Projectiles

Yarn shooting experiments were conducted to determine the ballistically-relevant, Young’s modulus and tensile strength of ultra-high molecular weight polyethylene (UHMWPE) fiber. Target specimens were Dyneema® SK76 yarns (1760 dtex), twisted to 40 turns/m, and initially tensioned to stresses ranging from 29 to 2200 MPa. Yarns were impacted, transversely, by two types of cylindrical steel projectiles at velocities ranging from 150 to 555 m/s: (i) a reverse-fired, fragment simulating projectile (FSP) where the flat rear face impacted the yarn rather than the beveled nose; and (ii) a ‘saddle-nosed projectile’ having a specially contoured nose imparting circular curvature in the region of impact, but opposite curvature transversely to prevent yarn slippage off the nose. Experimental data consisted of sequential photographic images of the progress of the triangular transverse wave, as well as tensile wave speed measured using spaced, piezo-electric sensors. Yarn Young’s modulus, calculated from the tensile wave-speed, varied from 133 GPa at minimal initial tension to 208 GPa at the highest initial tensions. However, varying projectile impact velocity, and thus, the strain jump on impact, had negligible effect on the modulus. Contrary to predictions from the classical Cole-Smith model for 1D yarn impact, the critical velocity for yarn failure differed significantly for the two projectile types, being 18% lower for the flat-faced, reversed FSP projectile compared to the saddle-nosed projectile, which converts to an apparent 25% difference in yarn strength. To explain this difference, a wave-propagation model was developed that incorporates tension wave collision under blunt impact by a flat-faced projectile, in contrast to outward wave propagation in the classical model. Agreement between experiment and model predictions was outstanding across a wide range of initial yarn tensions. However, plots of calculated failure stress versus yarn pre-tension stress resulted in apparent yarn strengths much lower than 3.4 GPa from quasi-static tension tests, although a plot of critical velocity versus initial tension did project to 3.4 GPa at zero velocity. This strength reduction (occurring also in aramid fibers) suggested that transverse fiber distortion and yarn compaction from a compressive shock wave under the projectile results in fiber-on-fiber interference in the emerging transverse wave front, causing a gradient in fiber tensile strains with depth, and strain concentration in fibers nearest the projectile face. A model was developed to illustrate the phenomenon.