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The ongoing pursuit of space and hypersonic flight continues to expose critical gaps in the understanding of material behavior under hypervelocity impact (HVI) and hypersonic flow conditions. Such limitations pose serious risks for aerospace vehicles, spacecraft, hardened structures, defensive systems, etc. Consequently, the development of materials and systems that can endure HVIs and hypersonic flight is a major obstacle in the quest for sustainable space exploration, reusable air-breathing hypersonic vehicles, and enduring protective structures. HVIs (≥ 3.0 km/s) can induce severe material deformation, erosion, fracturing, fragmentation, melting, vaporization, and sublimation. At the same time, hypersonic (≥ Mach 5) vehicles may be subjected to intense thermal and mechanical loads. Addressing these grand challenges requires a multifaceted and interdisciplinary approach, combining well-designed experiments with physics-based analytical and numerical modeling. Studying material behavior under HVIs and hypersonic conditions has been facilitated by two-stage light gas gun (2SLGG) aeroballistic ranges for almost seven decades. This current study surveys over 90 2SLGG aeroballistic ranges operational since 1990 to assess global launch and experimental capabilities. The 2SLGG's origins and research applications are explored, highlighting its significance in various fields, including shock physics, planetary science/defense, military defense, nuclear physics, hypersonic vehicle survivability and performance, and spacecraft micro-meteoroid/orbital debris protection. A summary of relevant HVI phenomena is presented to underscore the importance of 2SLGGs and to elucidate similarities and differences among various 2SLGG aeroballistic ranges and their supporting methods/tools. The 2SLGG's working principles are explained, and configurations and operations are compared. Modifications resulting in "three-stage light gas guns" are briefly mentioned for completeness. The full range of current 2SLGG performance capabilities is assessed with impact kinetic energies ranging from ∼ 10 joules to nearly 100 megajoules, and the facility survey results are used to explain the variations in aeroballistic range tankage, experiment types, research applications, and diagnostic systems. Finally, an overview of 2SLGG performance prediction methods is provided, featuring notable empirical, analytical, and numerical approaches. • Survey of over 90 2SLGG aeroballistic ranges active since 1990 worldwide. • 2SLGG's impact in multiple fields like military and space highlighted. • Detailed 2SLGG working principles and three-stage gun modifications explained. • 2SLGG performance spectrum from 10 J to 100 MJ detailed. • Variability in 2SLGG ranges and their scientific uses described. [ABSTRACT FROM AUTHOR]

• Created the first ballistic dataset for enhanced cross-laminated timber (ECLT). • Compared partial and full penetration results utilizing eight known ballistic resistant materials. • Developed benefit-cost assessment of panel configurations. Cross-laminated timber (CLT), an engineered wood product, has grown in popularity in the United States over the last decade due to its ease of assembly, aesthetic appeal, and potential to serve as a sustainable and renewable alternative building material. The improved robustness of CLT over light-frame timber structures has increased its potential in force-protected infrastructure that must resist blast waves and ballistic projectile penetration, but softwood CLT is typically not sufficient to fulfill standard criteria for ballistic threats. To address these threats, enhanced CLT (ECLT) composite panels were manufactured with layers of various reinforcing materials (e.g., steel, FRP) placed between wood laminations. These panels were tested against various ballistic threats during two sets of laboratory tests in order to provide a basis for future research. The first set of testing subjected laboratory-produced Southern Yellow Pine (SYP) ECLT to 84 shots of 0.50-inch (1.27 cm) steel sphere projectiles to evaluate the performance of various reinforcing materials, layups, and fastening methods. A subsequent set of tests subjected commercially produced ECLT of steel-reinforced Spruce-Pine-Fir (South) (SPF-S) to 36 shots of NATO ammunition projectiles traveling at realistic, standard striking velocities. Except for a panel using four layers of a thin and finely woven steel hardware cloth, steel reinforcement was effective in stopping projectiles from all three types of NATO ammunition fired. Ultimately considering the results of these two sets of tests, an initial cost-benefit structure was developed and discussed to compare ECLT configurations holistically, a multi-material wood analytical model framework was established and compared to experimental results, and the first ballistic experimental database for ECLT was created. [ABSTRACT FROM AUTHOR]

• Thermal modification does not significantly change the ballistic performance of coastal western hemlock CLT. • Density and hardness do no fully encompass the energy absorbing capacity of CLT under small arms ballistic threats. • Empirically fit UFC partial penetration equation formulations fit treatment specific datasets with minimal error. • One global UFC partial penetration equation can be utilized for design with an appropriate safety factor. To test and understand the potential for integration of thermally modified coastal western hemlock CLT systems in military applications, 109 ballistic experiments were conducted at the United States Army Engineer Research Development Center's Fragmentation Simulation Facility. For a range of CLT thicknesses, the depth of penetration and residual velocities were recorded for different striking velocities utilizing a 0.50 caliber steel sphere projectile. This information was used to compare and add to the existing ballistics data for CLT, investigate the effects of thermal modification on high strain rate loading of wood, assess physics-based empirical design equations used by the Unified Facilities Criteria, and evaluate energy absorbing behavior at a range of thicknesses and striking velocities. The experimental results showed that thermal modification does not significantly alter the full and partial penetration performance of coastal western hemlock CLT. However, the mechanism of fracture along the path of the projectile differed, which indicates that the model parameters used in the UFC design equation (density, hardness, and projectile properties) may not fully encompass the ballistic failure mechanisms of CLT. [ABSTRACT FROM AUTHOR]

Highlights • Ballistic impact tests on 4 mm thick Weldox 700 E steel plates struck by blunt rigid projectiles were conducted and a failure mode of shear plugging was identified in the tests. • The strength and fracture models of the steel were calibrated using a hybrid experimental-numerical method. • FE simulations were carried out by using either a modified version of the Johnson-Cook (MJC) fracture criterion or the Lode dependent Modified Mohr–Coulomb (MMC) fracture criterion. • FE simulations using the MJC and MMC fracture criteria predicted almost the same ballistic performance of the targets. • For targets of Lode dependent fracture, FE simulations showed that the Lode dependent fracture criterion would predict a much lower ballistic limit for less ductile targets. However, for targets with high ductility, introducing the Lode angle into the fracture criterion would not obviously alter the ballistic limit prediction. Abstract The necessity of incorporating the Lode angle into a fracture criterion in predicting ballistic resistance of ductile metal plates has not been well elucidated so far although the ductility of a metal may be Lode dependent. In this paper, 4.0 mm thick Weldox 700 E steel plates were fired by 5.95 mm diameter blunt rigid projectiles in a one-stage gas gun in the impact velocity range of 141.2 m/s∼275.7 m/s. A failure mode of shear plugging was observed in the test and the ballistic limit was obtained by fitting the initial-residual velocity data. An axisymmetric finite element (FE) model corresponding to the test was built in ABAQUS and then was utilized to predict the ballistic resistance and fracture behavior of the targets. In the FE model, a slightly modified Johnson-Cook constitutive relation was companied by either a Lode independent modified Johnson-Cook (MJC) or the Lode dependent modified Mohr–Coulomb (MMC) fracture criterion. The plasticity and fracture of the metal were fully calibrated by a series of mechanical tests under varying stress states, strain rates and temperatures. According to the tests and parallel FE simulations, it was found that the fracture of Weldox 700 E is obviously Lode dependent. However, ballistic simulations using the MMC and MJC fracture criterion predicted very close ballistic limit velocity and similar shear plugging failure mode when compared with the test results. The dominant stress state of the material failed in the process of shear plugging was revealed by detailed FE analysis and it was found that the ductility of the metal is quite different on the dominant stress state according to the two fracture criteria. To interpret the current simulation results, further FE simulations were carried out on fictitious metals and it was found that for less ductile metallic plates the MMC fracture criterion predicts a much lower ballistic limit velocity (as much as 22%) when compared with the simulation result from the MJC fracture criterion. In contrast, for metal plates with high ductility, the simulations from the two different fracture criteria would produce quite close ballistic limit velocity predictions. [ABSTRACT FROM AUTHOR]

Highlights • Created first-ever public ballistic data set for Cross-laminated Timber. • Related the ballistic performance to the species of wood found in the CLT (Spruce Pine Fir – South and Southern Yellow Pine). • Developed and calibrated models for predicting the embedment depth as well as residual velocity. Abstract Cross-laminated Timber (CLT) is a relatively new building material that has gained recent attention in the United States construction industry. CLT is a prefabricated, engineered wood product, composed of three or more plies of lumber with alternating ply directions. CLT is relatively strong and stiff, with the potential to meet the requirements for structures that are subjected to a variety of loading conditions. While CLT's response to static, dynamic (i.e., seismic), and fire loads has been characterized in the past, its response to the loads seen in force protection scenarios (i.e., blast or ballistic) is much less understood. In order to begin to fill this gap in knowledge, one of the first known sets of ballistic experiments were conducted on CLT and the results were used to develop and validate predictive models. This article describes the results of 122 ballistic experiments conducted at the United States Army Engineer Research and Development Center (ERDC). The experiments were conducted on two species of CLT of varying thicknesses: Spruce Pine Fir-South and Southern Yellow Pine. The experiments measured either penetration depth or residual velocity over a range of intermediate striking velocities. The effects of weathering (i.e., moisture content) were also explored on a data set. The results of the experiments were compared to existing United States Unified Facilities Criteria models for predicting the ballistic response of wood. The findings show the deficiencies in utilizing this wood model for CLT and explore alternate models for prediction. In general, it was found that models that incorporate both projectile and CLT target parameters most accurately predict the response. Most importantly, the results reinforce the necessity for re-calibration of models as new parameters are added to the CLT ballistic characterization database. [ABSTRACT FROM AUTHOR]

• Two field tests on concrete targets subjected to a projectile penetration followed by charge explosion were conducted. • The failure mode and stress waves in concrete were experimentally obtained. • Two-step numerical models based on the Kong-Fang concrete material model and SPG method were developed and validated. • The influences of projectile penetration on destructive effects caused by following charge explosion were clarified. The earth penetration weapons (EPWs) usually penetrate into protective structures firstly, and then detonate the charge to induce high-intensity blast stress waves to cause further damage. Existing investigations on the destructive effect caused by the following charge explosion after penetration of EPWs are very limited. To clarify the combined destructive effect in concrete material caused by an EPW, an experimental and numerical investigation on failure mode and stress wave propagation in concrete target subjected to a projectile penetration followed by charge explosion was conducted in the present study. Firstly, two field tests on high strength fiber-reinforced concrete targets subjected to a projectile penetration followed by charge explosion were conducted, in which the failure and blast waves in concrete targets were comprehensively obtained. Then two-step numerical models based on the Kong-Fang concrete material model and SPG method were developed and validated against the experimental data. Finally, based on the validated numerical models, the influences of projectile penetration on the destructive effect caused by following charge explosion were analyzed. The numerical results demonstrated that the damage caused by projectile penetration has significant influences on the final failure mode and stress wave propagation in concrete targets. The research results can provide an important reference for the design of protective structure against EPWs. [ABSTRACT FROM AUTHOR]

Highlights • Ballistic resistance evaluated for fabric-metal assemblies, as well as their metal and fabric components. • Significant effect of fabric-metal sequence on ballistic resistance of fabric-metal assemblies, which varies with number of fabric plies in the assembly. • Analysis of interaction between fabric plies and metal plate for various fabric-metal sequences. • Explanation of the influence of fabric-metal sequence on ballistic resistance based on the interaction between fabric plies and metal plate. Abstract Fabrics woven from high-strength fibres are increasingly employed for protection against projectile impact, because of superior mechanical properties. In some applications, high-strength fabrics are combined with metallic components to provide sufficient structural rigidity and strength – e.g. for vehicle bodies, turbine engine fragment barriers, building doors, etc. An understanding of how the fabric-metal layer sequence affects the resulting ballistic resistance, is essential for effective design of such fabric-metal assemblies. This motivates the current study, whereby multiple plies (1, 2 or 4) of Twaron (T) aramid fabric were combined with an aluminium alloy (A) thin plate to form a lightweight protective panel. The projectile impact penetration resistance of three types of fabric-metal arrangements were examined – i) the aluminium alloy plate as the impact face; ii) the Twaron fabric as the impacted layer; iii) the aluminium alloy plate sandwiched between fabric layers. For assemblies with a smaller number of fabric plies (i.e. 1 or 2), siting the aluminium alloy plate as the rearmost layer results in a significantly higher impact energy absorption capacity, compared to having the aluminium alloy plate as the impact face – e.g. for (A+1T) assemblies, i.e. Al plate+1 ply of Twaron, 1T/A (impact face layer appears first in this nomenclature) performs much better than A/1T. For (A+2T) assemblies, 2T/A provides the highest impact resistance, A/2T is the weakest, and 1T/A/1T lies in between. However, when the number of fabric plies is increased to 4, a variety of responses was observed. An A/4T configuration absorbs significantly higher energy than a 4T/A arrangement, while a symmetrical 2T/A/2T sequence absorbs less energy than either an A/4T or 4T/A configuration. High-speed optical photography images and post-test specimens were analysed, to examine the deformation and failure modes of the fabric plies and Al plate in the fabric-metal targets, and how they are affected by the fabric-metal sequence. These help identify the interaction between the fabric plies and Al plate for various fabric-metal sequences, in order to account for the phenomena observed in experiments. [ABSTRACT FROM AUTHOR]

Abstract To study the aeroengine containment capability at high temperatures, experimental and numerical investigations have been carried out to determine the ballistic performance and energy absorption characteristics of GH4169 alloy thin plates at temperatures ranging from 25–600 °C. First, experiments were conducted using a gas gun. Target plates were impacted by projectiles with various initial velocities. The effects of the temperature and initial velocity on the deformation, failure pattern and energy absorption of the plate were correspondingly obtained. The experimental results showed that at higher temperature, the deformation of the target plates is greater, the energy absorbed by the target plates is smaller and the ballistic limit velocities are lower. The petal deformation of the target plate caused by bending is severe at the temperature of 600°C. Second, numerical simulations of the impact were conducted by an explicit dynamics FE code (LS-DYNA). The Johnson-Cook constitutive model with parameters obtained from split Hopkinson pressure bar (SHPB) experiments was used to describe the materials properties of the plates at various temperatures and strain rates. It was found that the numerical results are consistent with those obtained by the ballistic experiments. In addition, the results of the numerical simulations also showed that the ballistic limit velocity of the target plate exhibits an approximately linear relationship with the temperature of the target plate. The energy absorbed by the target plate is decreased by 18% and 9% at 600 °C and 300 °C, respectively, compared with that at 25 °C. [ABSTRACT FROM AUTHOR]

Highlights • Cavity dynamics in gelatin was studied. • A motion model of temporary cavity is established in gelatin penetrations of rifle bullets. • The motion model is well consistent with the penetration tests. • The radial movement of cavity is characterized by the behavior of bullet and the characteristic velocity. Abstract In wound ballistics, modeling the penetration-cavitation dynamics will set the basis for evaluating the damaging efficiency of projectiles. In our previous study, a motion model to characterize the behavior of rifle bullets has been established and verified in the gelatin penetration. In order to reveal the cavity production analytically, in combination with parameters obtained from the motion model of rifle bullet, cavity dynamics in gelatin was studied and a motion model of temporary cavity in gelatin penetrations of rifle bullets was proposed and verified by comparison with experimental results in terms of maximum cavity wall radius, radial movement along the penetration trajectory and temporary cavity profiles. It can be concluded that calculated results of the cavity motion model agree well with experiment data for penetration of 7.62 mm and 5.56 mm rifle bullets. And the radial movement of cavity can be characterized by the behavior of bullet and the characteristic velocity. It is significant for the trauma assessment to develop an appropriate cavitation model in gelatin for penetrations of rifle bullet. [ABSTRACT FROM AUTHOR]

Highlights • Pressurized borosilicate glass cylinders were tested under high-velocity impact. • Efficiency of elastomeric coating on ballistic damage was investigated. • Drop tower testing was added to verify air gun results on the cylinders. • Critical coating thicknesses to prevent initiation of ballistic damage to porcelain bushings was estimated. Abstract Pressurized borosilicate glass cylinders were used to (1) simulate experimentally high-voltage transformer bushing behavior under high-velocity impact from an air gun, (2) investigate fragment dynamics to estimate the impact range of airborne fragments, and (3) evaluate the efficiency of an elastomeric coating on ballistic damage initiation and fragment confinement. Using high-speed cameras, the velocities and directions of ejected fragments from the cylinders were determined along with fragment distribution symmetry. Drop tower testing was added to independently verify the air gun results on the cylinders through a different test under similar impact energies using flat samples of the same glass. Elastomeric coatings were also applied to both the cylinders and flat samples to increase their resistance to high energy impact. It has been shown that internal pressure in the glass cylinders plays a major role in the failure modes during high-velocity impacts. This pressure affects velocities, directions, and symmetry of fragment distribution. The fragment impact range investigation turned out to be inconclusive due to highly erratic behavior of the fragments after the blast. Most importantly, it has been ascertained that fragment dynamics are drastically altered by elastomeric coatings, producing a high level of fragment confinement both in the drop tower and gun tests. By extrapolating the air gun and drop tower data out to high power rifle energy levels, unique predictions of the critical coating thicknesses to prevent the initiation of ballistic damage and to confine fragments in borosilicate glass cylinders and C-120 porcelain bushings were achieved for the first time. [ABSTRACT FROM AUTHOR]

The ability of a metallic surface layer to protect CFRP cross-ply plates against perforation is explored. Aluminium alloy plates (either AA1050A or AA6082-T6) were placed in front of a CFRP layer, and the bilayer was subjected to either quasi-static indentation or to ballistic impact by a spherical projectile, with rigid back support or an edge-clamped boundary condition. The observed perforation mechanism of the CFRP layer is neither influenced by the presence of the metallic layer nor by the choice of loading rate (i.e. quasi-static versus ballistic). In the back-supported condition, the CFRP layers fail by an indirect tension mode that consists of tensile failure of plies in the material directly beneath the indenter or projectile. Alternatively, in the edge-clamped condition, the CFRP layers fail by a shear plugging mechanism. Although the presence of metallic layers does not suppress the shear plugging of the underlying CFRP layer, the loaded area in the CFRP layer increases by the addition of the protective metallic layer, thereby increasing the perforation resistance of the CFRP layer. [ABSTRACT FROM AUTHOR]

Hypervelocity impact of a projectile on a thin plate generates a debris clouds. Largest chunk (mass) of the projectile material (called primary fragment) in the cloud poses significant ballistic threat to subsequent structure. Primary fragment characteristics (mass, velocity and exit angle) are used in assessing subsequent structure damage potential. Non-dimensional empirical equations are proposed in this paper for estimation of these characteristics. A set of simulations has been carried out using smoothed particle hydrodynamics (SPH) technique of Autodyn. Two stage light gas gun test data has been compared for validation of simulation. Simulation results for spherical projectile made of stainless steel impacting mild steel plate with impact velocity of 2–4 km/s and obliquity of 0°–60° has been analysed. Constants and radicals of the proposed equations are determined by multi variable regression of the simulation data. Comparison of the simulation data with the proposed equations shows a very good fit. [ABSTRACT FROM AUTHOR]

Modeling fiber-reinforced composites and fabrics in ballistic applications can be difficult after the initiation of damage and failure. Mesoscale models can provide accurate results, but they are much more computationally intensive than standard continuum approaches. However, an accurate continuum model for these materials requires a thorough understanding of the relevant deformation and failure mechanisms. A new continuum modeling approach was developed in which the average stresses and strains within a composite containing multiple fiber orientations are related at the element, lamina, and constituent length scales using rules of mixtures. The new approach was used to simulate a variety of mechanical and ballistic test data from different composite and fabric materials. The accuracy of the results demonstrates the predictive capability of the new model to reproduce deformation and damage of composites under generalized loading conditions. [ABSTRACT FROM AUTHOR]

The ballistic performance of monolithic targets perforated in ductile formation by rigid projectiles can be reasonably approximated by an energy balance based on the work done in expanding a hole from zero initial radius to that of the penetrating projectile. For a specific projectile, these energy balance laws can be expressed in terms of a simple scaling law which requires an empirical fit to ballistic data. However, once this fit has been performed for a specific projectile against a specific target material, predicting the performance of other materials against this projectile can be done from a simple quasi-static compression stress–strain curve, provided the target is perforated in ductile hole formation. Four variations of ductile hole formation analytical and semi-empirical models have been reformulated as scaling laws and evaluated for their ability to characterise the performance of monolithic aluminium plates impacted by 7.62 mm APM2 projectiles at normal incidence. The database used to fit and evaluate the performance of the scaling laws incorporates more than 1600 V 50 measurements against 24 different alloys and tempering/strain-hardening combinations with thicknesses ranging from 16.2 to 63.5 mm. The highest performing scaling law formulation was found to characterize the measured V 50 to within 5% of the experimental value for over 97% of the database entries. Further improvements in accuracy are likely impossible when representative stress–strain curves are used for performance characterization rather than tests of each individual plate used in the ballistic tests. The scaling law can be applied to predict the performance of targets perforated in ductile hole formation with a high level of confidence, an example of which is provided for the 12.7 mm APM2 projectile against a range of aluminium alloys. [ABSTRACT FROM AUTHOR]

• Ballistic, a high strain-rate method, used to produce functionally graded materials. • Hardness and microstructures are studied as functional properties. • Axisymmetric & unsymmetrical variation can be achieved. • The variation can be controlled by the leading edge shape, speed, & target material. 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. [Display omitted] [ABSTRACT FROM AUTHOR]

We report an increase in penetration resistance of front-facing fluorinated polymer coatings applied to hardened steel substrates. The study included monolithic and laminate configurations and examined their ability to improve the ballistic penetration resistance of selected substrates. Polytetrafluoroethylene (PTFE) coatings substantially improved the V-50 performance and outperformed similar polymer-coated armor composites for thicker coating layers. The thickness and hardness of steel substrates, polymer layer thickness, and cumulative number of laminates collectively influenced the mass efficiency. Since PTFE is a crystalline material that, unlike previously tested polyurea and other elastomers, does not undergo an impact-induced phase transition, its high performance suggests that this material resists flow during impact and, subsequently, reduces the strain imparted to the substrate. The fluoropolymer offers a lightweight and simple solution to enhance ballistic armor systems. [ABSTRACT FROM AUTHOR]

The ballistic response against small projectiles of a hybrid laminate made up of a front layer of a needle-punched nonwoven fabric and several layers of a woven fabric was analyzed from the experimental and numerical viewpoint. The experimental results showed that the hybrid shield outperformed the woven and nonwoven counterparts in terms of the ballistic limit and of the energy dissipated, which was larger than the sum of the energies dissipated individually by the woven and nonwoven fabrics. Moreover, the energy absorption of the hybrid shield was maintained above the ballistic limit, leading to a ballistic performance similar to the one reported in fiber-reinforced composites. In fact, the hybrid polyethylene shield presented better impact performance than conventional laminates based on aramid woven fabrics with similar areal weight. The mechanisms responsible for the ballistic performance of the hybrid shield were ascertained by means of numerical simulations. The deformation and failure mechanisms obtained in the numerical simulations were in agreement with the experimental results and showed the complex interaction between the projectile, the nonwoven and the woven fabrics during impact which led to an enhanced energy absorption capability. [ABSTRACT FROM AUTHOR]

Although many aspects of the fracturing process of concrete are now well understood and successfully simulated with various models, it is still very difficult to properly simulate the different failure mechanisms observed in a concrete structure induced by ballistic impact. In this paper, an enhanced version of the effective-rate-dependent nonlocal damage model [Eng. Fracture Mechanics, 176 (2017)] is proposed to simulate the response of concrete in such events. Hydrostatic damage has been added to the formulation in order to take the damage of the material matrix observed while porosity reduces during compaction into account. Besides controlling the evolution of the nonlinear volumetric response of the material, this new damage variable contributes to the deterioration of the material stiffness upon confinement. It is demonstrated that the description of the nonlinear volumetric response of concrete by an equation of state (EOS) as a plasticity phenomenon, as it is commonly done in hydrodynamic constitutive modeling, is unrealistic for concrete. Such formulations fail to represent the effect of the loss of cohesion observed during compaction on the deviatoric response of the material. By taking this phenomenon into consideration, the proposed model systematically predicts the relevant failure modes (cratering, tunneling, radial cracking and spalling) observed during ballistic impact on a concrete plate as a function of the projectile velocity and plate thickness. [ABSTRACT FROM AUTHOR]

The effect of confinement on the localized impact response of ceramic and cermet tiles is investigated. A scoping study was first conducted using alumina and TiC/Ni cermet tiles encased in a metal matrix composite (MMC) and impacted by high velocity steel balls. The investigation revealed that increasing the MMC casing thickness reduced the cracking in the ceramic (alumina) tile but had a much smaller effect on the cermet tile. This motivated a detailed experimental investigation of the effect of lateral confining pressure on the static and dynamic indentation response of granite and Corian ® tiles that serve as model ceramic and cermet materials, respectively. Quasi-static indentation resulted in comminution under the indenter and the formation of radial cracks in the granite tiles, with the number of radial cracks decreasing with increasing confining pressure. By contrast, the plastic indentation and small shallow radial cracks observed in the Corian ® tiles were unaffected by variations in the confining pressure. The loading imposed by the high velocity impact of a steel ball resulted in conical and lateral cracks as well as radial cracks and comminution in the granite tiles. Intriguingly, while the cone and radial cracks were suppressed by confining pressure, the lateral cracks appeared only at the higher confining pressures. By contrast, the strain rate sensitivity of the yield strength of the Corian ® reduced the plastic indentation under dynamic loading, but this in turn promoted the formation of radial cracks which decreased in number with increasing confining pressure. No lateral cracks, conical cracks or comminution was observed in the Corian ® . The study shows that confining pressure has a less significant effect on cermets compared to ceramics. Since confinement systems add considerable weight to ceramic-based ballistic protection systems, this study suggests that the use of lightly confined cermets could reduce the overall weight of ballistic protection systems. [ABSTRACT FROM AUTHOR]

Mechanisms of projectile defeat and ballistic resistance of thin targets impacted by tip-deformable conical projectiles have been discussed in the context of the influence of apex angle of the projectile. Transition in target local failure modes occurred as the projectile apex angle was altered. The effect on projectile deformation and ballistic properties has also been discussed. A brief discussion on projectile deformation mechanism and projectile defeat near ballistic limit velocities with supporting experimental evidence is included. Numerical simulation using ABAQUS/Explicit has been able to effectively predict the projectile deformation and associated target behavior. [ABSTRACT FROM AUTHOR]

This study systematically investigates the effect of Shear Thickening Fluid (STF) treatment on the high strain rate properties of UHMWPE (Ultra High Molecular Weight Poly Ethylene) composites. Spherical nanosilica particles of size 100 nm were used for the synthesis of STF. The high strain rate impact studies were accomplished on in-house designed and fabricated Split Hopkinson Pressure Bar (SHPB) experimental set-up. Compression moulded UHMWPE variant Gold Shield ® was used as the ballistic composite. Both STF-treated as well as neat Gold Shield ® specimens were subjected to high strain rate impact testing. From the experimental results and Fractography studies it was revealed that STF treatment enhanced the ballistic resistance of Gold Shield ® composite material. In the SHPB experiments, the improved ballistic performance of STF-treated Gold Shield ® specimens was manifested in terms of higher peak stress, specimen strain rates and impact toughness. [ABSTRACT FROM AUTHOR]

We investigated the ballistic resistance of hot-rolled structural steel plates with a nominal yield stress of 355 MPa in this study. Ballistic tests were conducted with 7.62 mm armor piercing bullets on monolithic and multi-layered configurations both in the as-received (AR) state and in a case-hardened (CH) state. In the CH state we made the surface stronger while preserving a relatively ductile core. This was done to improve the ballistic properties of the plates. Quasi-static uniaxial tension tests and Vickers hardness tests were conducted to calibrate constitutive models for numerical simulations. The ballistic tests revealed that the capacity was highest for a monolithic CH plate, and that case hardening increased the perforation resistance by more than 20%. Plate layering decreased the capacity of the CH plates, while the capacity of the AR plates did not decrease consistently by increasing the number of layers. Finally, we used the hardness measurements to distribute material properties across the thickness of the CH plates. These distributed material properties were used in numerical models. Finite element simulations gave predominantly conservative results within 11% of the experimental values. [ABSTRACT FROM AUTHOR]

This research deals with the experimental and numerical investigation of ballistic protection provided by a combination of perforated and base armour plates. A 7.62 mm armour piercing projectile was used during the experimentation to determine the ballistic response of an aluminum base armour plate and a combination of steel perforated and aluminum base armour plate. The armour piercing projectiles were able to penetrate the base armour plate while the combination of perforated and base armour plates was able to stop the penetration of the armour piercing projectile. A finite element method based numerical model was developed to investigate the defeating phenomenon of perforated and base armour plate combination. The brittle fracture caused by the bending of the projectile core due to the asymmetric impact was predicted and the resulting fragments of the projectile were unable to penetrate the base armour plate. Craters were formed on the surface of the base armour plate from the impact of the projectile fragments. The numerical model was able to predict the hole growth and penetration of projectile when only the base armour plate was impacted by the projectile. [ABSTRACT FROM AUTHOR]

The ballistic performance of plain, reinforced and prestressed concrete targets of unconfined compressive strength 48 MPa was studied experimentally against long rod steel projectiles. The square targets (450 mm × 450 mm) of thicknesses 60, 80 and 100 mm were subjected to normal impact by 1 kg ogive nosed hardened steel projectiles of diameter 19 mm and length 450 mm. The reinforcement in the reinforced and prestressed concrete targets was provided with respect to φ8 mm @80 mm c/c both ways. An initial prestress of approximately 4–5 MPa (10% of unconfined compressive strength) was also induced in the prestressed concrete targets with the help of 4 mm diameter steel wires of ultimate tensile strength 1646 MPa. The experiments were carried out at varying incidence velocities, 65 - 220 m/s, and the results thus obtained with respect to extent and vicinity of damage, volume of spalling and scabbing as well as ballistic resistance for three distinct concretes have been compared and discussed. The reinforcement in the concrete has been found to be effective in minimizing the scabbing and spalling of material. The initial prestressing in the concrete, stimulated the globalization effect in the deformation process and thus improved the ballistic performance. The ballistic limit of reinforced concrete target was 11, 16 and 26% higher than plain concrete target for 60, 80 and 100 mm thicknesses respectively. On the other hand, the ballistic limit of prestressed concrete targets was found to be 19, 25 and 35% higher than reinforced concrete, and 32, 45 and 70% higher than plain concrete target for 60, 80 and 100 mm thicknesses respectively. [ABSTRACT FROM AUTHOR]

The effect of matrix shear strength on the ballistic response of simply-supported carbon fibre reinforced plastic (CFRP) beams was explored for a flat-ended projectile. To gain insight into the deformation and failure mechanisms, the following additional tests were performed on CFRP beams: (i) quasi-static indentation tests with rigid back support and, (ii) quasi-static cropping tests. In all 3 types of tests, CFRP [0°/90°] cross-ply laminates were tested in six states of cure, such that the matrix shear strength ranges from 0.1 MPa to 100 MPa. In the quasi-static cropping tests, the composite beams failed by shear plugging (involving transverse matrix cracks, ply delamination, and fibre fracture). In contrast, indirect tension (by ply tensile failure in the fibre direction) occurred in the back-supported quasi-static indentation tests. In the ballistic tests, the CFRP beams of high matrix shear strength (30 MPa–100 MPa) failed by a shear plugging mode. When the matrix shear strength was less than 30 MPa, the failure mode and the penetration velocity doubled and occurred by indirect tension. The optimal shear strength to give adequate static and ballistic strength is on the order of 20 MPa. [ABSTRACT FROM AUTHOR]

This paper investigates experimentally and numerically methods to enhance the ballistic performance of ceramic armor. Initially we demonstrate an experimental set-up to impose pre-stress to ceramic-metal bi-layer armor and study the depth of penetration to measure the ballistic efficiency as a function of pre-stress intensity validating our previous numerical studies on effect of pre-stress on the ballistic limit of ceramic armor ( Int. Journal of Impact Engineering, 2015(84)159-170 ). Secondly, a module is designed and tested to achieve interface defeat in ceramic armor with multiple interface layers. Finally, influence of thickness of the steel cover plate (CP) on ballistic performance of SiC ceramic is studied through AUTODYN ® finite element simulations for normal and oblique (NATO 60°) against long rod projectile (LRP) with a conical tip. The LRP and CP are modeled using smooth particle hydrodynamic (SPH) particles and rest of the component is modeled using Lagrangian domain. The numerical analyses of armor modules are compared via depth of penetration (DOP) and LRP residual length for varying cover plate thicknesses. [ABSTRACT FROM AUTHOR]

This paper presents the results of an investigation of the ballistic limits and failure modes of AA2024-T351 sheets impacted by cubical projectiles. The effect of cube orientation on the ballistic limit and failure modes was considered in detail. Three impact configurations were investigated. Configuration one, two and three considered face, edge or corner impacts correspondingly. The experimental results were complemented with finite element analysis results in order to explain the observations. The lowest ballistic limit (202 m/s) was observed when the cube edge impacted on the target. In the cube face impacts, the ballistic limit was higher (223 m/s), and the highest ballistic limit (254 m/s) was observed for the corner impact. Although the face impact did not have the lowest ballistic limit, this impact configuration resulted in the least amount of projectile energy loss for impacts above the ballistic limit. With the aid of finite element modelling, it was possible to develop a better understanding of the test results and explain that the observed differences in impact response were not just due to a difference in projectile frontal area, but also due to the combination of the localised deformation near the projectile impact point and the resulting global (dishing) deformation. [ABSTRACT FROM AUTHOR]

The penetration of rigid projectiles in polycarbonate (PC) targets is explored through deep indentation tests with conical-nosed indenters and ballistic penetration results for armor piercing 7.62 mm projectiles. We found that the resistance to penetration in both sets of experiments is practically the same, which means that the rate sensitivity of PC does not play a significant role in its resistance to penetration. We account for this observation by including the pressure dependence of the elastic constants and the strength of PC in its constitutive equation, which we implemented in numerical simulations. This pressure-dependent constitutive relation resulted in good agreements between simulation results and experimental data for both penetration depths and residual velocities of armor piercing projectiles impacting PC targets. [ABSTRACT FROM AUTHOR]

The present paper deals with the ballistic testing and numerical modeling problems of fragment penetration of glass fabric/epoxy-phenolic (GFRP) laminates. Two laminates of different thickness (1.95 and 3.90 mm) were subjected to ballistic impact of 6.35 mm dia steel sphere as a fragment simulator at different velocities to get ballistic curves. There were developed the continuum-based model (CBM) and the microstructural model (MSM) of GFRP laminates in two finite element codes (AUTODYN-3D and LS-DYNA). The CBM is a model of anisotropic body with the fiber-dominated failure mechanics. The advantages of this model include short CPU time and good prediction of ballistic limit velocity with the use of only two free parameters of failure model to be determined from preliminary dynamic experiments. The MSM has geometrically accurate GFRP structure and assumption of isotropy and simple failure criteria of constituents (fiber bundles and matrix) not only to get the ballistic limits, but also to describe in details the damage mechanisms of GFRP laminates. The numerical simulation results showed a good correlation with the experimental data in terms of ballistic curves and internal material damage. [ABSTRACT FROM AUTHOR]

In this paper in order to try and elucidate the effects of particle morphology on ballistic response of comminuted systems, a series of experiments were carried out via the use of powder compacts with differing initial particle morphologies. This approach provided a route to readily manufacture comminuted armour analogues with significantly different microstructural compositions. In this study pre-formed ‘fragmented-ceramic’ analogues were cold-pressed using plasma-spray alumina powders with two differing initial morphologies (angular and spherical). These compacts were then impacted using 7.62 mm FFV AP (Förenade Fabriksverken Armour Piercing) rounds with the subsequent depth-of-penetration of the impacting projectile into backing Al 6082 blocks used to provide a measure of pressed ceramic ballistic response. When material areal density was accounted for via differing ballistic efficiency calculations a strong indication of particle morphology influence on post-impact ceramic properties was apparent. These results were reinforced by a separate small series of plate-impact experiments, whose results indicated that powder morphology had a strong influence on the nature of compact collapse. [ABSTRACT FROM AUTHOR]

We present a novel methodology to experimentally verify constitutive models and numerical algorithms used in terminal ballistics of small arms ammunition. The methodology comprises of the following elements: identification of material models in a set of independent tests, terminal ballistics testing of conditions covering the most important cases of bullet–target interactions, while providing enough data to assess the scatter of parameters measured in the experiments and to create a measure characterising deviation of modelling results from the experiments. To meet the objectives of this study, 7.62 mm armour-piercing ammunition was used to perforate steel armour plates at ordnance velocity. Several parameters that characterise bullet velocity and path, plate deformation and ductility were measured and used as reference data for the verification of models. Relatively complex and simple constitutive and failure models implemented in the Finite Elements (FE) code LS DYNA were used. Finally, solid Lagrange and hybrid solid/Sooth Particles Hydrodynamics (SPH) discretisation methods with detailed models of the bullet and target are presented and different findings are compared with ballistic test results. The methodology shows a significant efficiency in the assessment of the adequacy of models. In this study, stress triaxiality and strain rate based models were found to give results in good agreement with experimental results, and several physical mechanisms are well predicted. [ABSTRACT FROM AUTHOR]

This paper describes the damage development in ceramics with and without composite cover during ballistic impact. This is relevant for ceramic inserts in body armor that are often covered with a composite material. To study the effect of the cover on the damage development in the ceramic, projectile impact experiments were performed at sub-muzzle velocities on bare alumina tiles and plates covered with a fiberglass composite. In addition to the experiments, finite element simulations were performed. An atypical formulation was used; Arbitrary Lagrangian–Eulerian (ALE) for the projectile and Lagrangian for the ceramic target. For the ceramic target, an unconventional material model was chosen; the pseudo-geological model 72_R3 in LS-DYNA. Cracking damage in the recovered plates was characterized in a manner that clearly distinguished between cracking mechanisms and allowed the cracks to be tracked and quantified. In light of the common use of composite cover for ceramics in body armor, an unexpected result was found; that the covered plates showed significantly more damage than the bare plates. The simulations successfully matched details of the cracking patterns and elucidated the damage evolution in the ceramic plates. The simulation results explained the damage observations as the result of restraining effects, i.e. the restraining effect of the composite cover keeps the damaged ceramic in the path of the projectile resulting in increased damage. [ABSTRACT FROM AUTHOR]

Finite element analysis of the impact of 7.62AP bullets on ceramic/aluminum bi-layer hybrids was carried out using AUTODYN hydrocode. Johnson–Cook material model was used for the metal and Johnson–Holmquist model was used for the ceramic. The models were validated with experiments conducted on Al 2 O 3 /Al 5083 and AlN/Al 5083 bi-layer composites. It has been observed that AlN ceramics has superior performance in defeating the bullet in comparison to Al 2 O 3 ceramics. Deformation of the backing plate and the corresponding plastic strain energies are considered in this study for the parameters of performance. The results will enable the design of materials for developing an efficient structure for the protection against the impact of 7.62AP bullets at ordnance velocities. [ABSTRACT FROM AUTHOR]

The ballistic perforation response of knits formed from continuous filament aramid is reported and compared to conventional armor textiles and commodity fabrics. The ballistic experiments consist of 6.0-mm-diameter glass spheres impacted into gelatin-backed targets with areal densities from 200 to 1000 g/m 2 . These ballistic experiments are complemented with quasistatic reverse-perforation experiments to gain insights into deformation and failure for these materials. In-plane stretch experiments are also performed to quantify modulus and strain-to-failure. The results show that, while the ballistic performance of traditional woven textiles is generally superior to knitted aramids, knits formed from continuous filament aramid are significantly better than knits formed from staple yarn. Knitted structures are limited by two main factors: failure of a single yarn tends to lead to catastrophic deconstruction and perforation, and the low in-plane modulus of knits leads to poor lateral stress transfer and energy distribution during higher speed impact. Importantly, however, knits provide significantly more reversible elongation with less elastic resistance compared to other structures, such as woven textiles, making them well-suited for wearable protection in which comfort is critical. The results also show that continuous filament knits can be produced with commercial manufacturing equipment, and that barriers composed of few layers of high-denier yarn knits likely provide more efficient ballistic resistance than equivalent weight barriers composed of many layers of low-denier yarn knits. [ABSTRACT FROM AUTHOR]

Hybrid composite laminates consisting of woven Kevlar fiber fabric, epoxy and AA 5086-H32 aluminum sheets were produced and the effects of addition of micro and nano-fillers to the fiber on ballistic response of the hybrid laminates were investigated. The micro and nano-fillers used in this study are powders of aluminum, gamma alumina, silicon carbide, colloidal silica and potato flour. They were introduced into the Kevlar fabrics by mixing with polyethylene glycol (PEG-400), followed by impregnation of the Kevlar fabric with the mixture and drying to eliminate the solvent. The energy absorption by the hybrid composite laminates containing the various nano-fillers under ballistic impact were determined and compared with laminate containing no nano-filler impregnation. The ballistic impact resistance of the produced hybrid composite laminates was tested according to NATO standards using a caliber 270 Winchester rifle. The projectile penetration and the resulting perforations of the hybrid laminates were studied in order to determine the influence of the deposited nano-fillers on Kevlar fibers on their energy absorption and impact resistance. The relationship between areal density and energy absorbed are discussed to determine which specimens perform better under ballistic impact. Protection levels achieved by targets were analyzed in relation to the initial impact energy from low caliber weapons. The results indicate that the ballistic impact resistance and impact energy absorption of the hybrid composite laminates were enhanced by deposition of micro and nano-fillers into surface of the Kevlar fibers fabrics. The highest impact energy absorption capacity was achieved by deposition of aluminum powder followed be colloidal silica and silicon carbide powder in that order. Addition of gamma alumina powder and potato flour has produced the least effect of enhancing the impact energy absorption capability of the laminates. These findings indicate that introduction of micro- and nano-fillers coating on Kevlar fabrics using PEG-400 is a promising method for strengthening interfacial bonding between the matrix and fibers in hybrid composite laminates. [ABSTRACT FROM AUTHOR]

The ballistic performance of an ultra-high hardness armour steel (UHA) has been evaluated for a range of thicknesses and obliquities against armour piercing (AP) and fragment simulating projectiles (FSPs). Together with published literature, these results enable the effect of plate hardness on performance against both AP and FSP threats to be characterized over a range of plate hardnesses from ~ 300 to 600 HB. For AP projectiles, a complex relationship was observed that corresponded well with historical phenomenological curves describing the effect of varying projectile and armour failure mechanisms. In the ultra-high hardness regime (> 570 HB), against AP projectiles with core hardnesses of 610–745 HB (i.e. 7.62 mm APM2 and 12.7 mm APM2 projectiles), projectile shatter was demonstrated to be the controlling mechanism of armour performance. Against much softer FSPs (281 HB), where projectile shatter is not a relevant mechanism, the armour performance was found to initially decrease with increasing plate hardness up to ~ 450 HB due to increased susceptibility to adiabatic shear plugging. Above ~ 450 HB the performance was observed to plateau. The observed performance plateau appears to relate to a critical threshold for adiabatic shear failure beyond which further increases in plate hardness will not result in a decrease in performance. A number of common empirical and analytical models were applied to reproduce the experimentally-determined relationship between hardness and penetration resistance, none of which were able to qualitatively or quantitatively reproduce the observed relationships for either projectile class. [ABSTRACT FROM AUTHOR]

For both ethical and practical reasons accurate tissue simulant materials are essential for ballistic testing applications. A wide variety of different materials have been previously adopted for such roles, ranging from gelatin to ballistics soap. However, while often well characterised quasi-statically, there is typically a paucity of information on the high strain-rate response of such materials in the literature. Here, building on previous studies by the authors on other tissue analogues, equation-of-state data for the elastomeric epithelial/muscular simulant material Perma-Gel ® is presented, along with results from a series of ballistic tests designed to illustrate its impact-related behaviour. Comparison of both hydrodynamic and ballistic behaviour to that of comparable epithelial tissues/analogues (Sylgard ® and porcine muscle tissue) has provided an insight into the applicability of both Perma-Gel ® and, more generally, monolithic simulants for ballistic testing purposes. Of particular note was an apparent link between the high strain-rate compressibility (evidenced in the Hugoniot relationship in the U s -u p plane) and subsequent ballistic response of these materials. Overall, work conducted in this study highlighted the importance of fully characterising tissue analogues – with particular emphasis on the requirement to understand the behaviour of such analogues under impact as part of a system as well as individually. [ABSTRACT FROM AUTHOR]

• High hardness steel (HHS) sheet with UHMWPE composite backing were tested against a hardened steel core projectile. • The projectile core was eroded by the HHS sheet and stopped in UHMWPE composite. • It is observed that only a core eroded to a certain length and weight by armor system can be defeated. • In numerical modeling core failure strain was determined from the residual weight of cores. • The numerical model can be used to evolve armor design. Thin high hardness steel sheets can be an alternative to expensive ceramic armor systems designed to defeat hardened core projectiles. A thin high hardness steel sheet backed with UHMWPE fiber-reinforced composite was ballistically tested against a 7.62 × 39 mm hardened steel core projectile in a single-stage gas gun. Thin steel sheets of 530 BHN hardness were adhesively bonded with UHMWPE fiber-reinforced composite to fabricate armor plates. Armor plates were able to defeat the projectile showing considerable potential. Tensile strength of steel sheet and UHMWPE-fiber reinforced ply was also determined. A detailed numerical simulation of the impact event was also performed to understand the phenomenon of defeat and penetration in greater detail. The numerical model was calibrated from the recovered projectile's core after the ballistic test. [ABSTRACT FROM AUTHOR]

Ultrafine grained tungsten-based alloys are promising kinetic energy penetrator materials because of their high strengths and densities, making them ideal for penetration into concrete and geomaterials. However, there are difficulties in evaluating their ballistic performance using traditional testing techniques because ultrafine grain sizes are challenging to achieve in bulk parts. In this letter, we performed sub-scale ballistic experiments where ultrafine tungsten alloy cores were fired into concrete targets using small caliber projectile assemblies. The results suggest that sub-scale testing may be used as a screening tool for advanced kinetic energy penetrator materials that are more easily prepared in smaller geometries. [ABSTRACT FROM AUTHOR]

Behind helmet blunt trauma (BHBT) has emerged as a serious injury type experienced by soldiers in battlefields. BHBT has been found to range from skin lacerations to brain damage and extensive skull fracture. It has been believed that such injuries are caused by forces transmitted from the helmet's back face deformation (BFD), which result in local deformations of the skull and translation or rotation of the head, leading to brain injuries. In this study, head injury risks resulting from the BFD of the Advanced Combat Helmet (ACH) under ballistic impact are evaluated using finite element simulations. The head model developed at KTH in Sweden is adopted, and a helmet shell model (including foam pads) is constructed. The examined mechanical parameters include the maximum von Mises stress in the skull, pressure (mean normal stress) and maximum principal strain in the brain tissue, contact force, and head acceleration. The influences of the foam pad hardness, stand-off distance, helmet shell thickness, and impact direction on head injury risks are studied. It is found that a softer foam pad offers a better protection, but the foam pad cannot be too soft. Also, it is shown that a slightly larger stand-off distance leads to a significant reduction in head injury. In addition, the simulation results reveal that an increase in the helmet thickness reduces the injury risk. It is further observed that a 45-degree oblique frontal impact results in a lower head injury risk than a 90-degree frontal impact. Moreover, for a helmet protected head under ballistic impact, it is seen that a high risk of skull fracture does not necessarily mean an equally high risk of injury to the brain tissue. The predictions from the current model of a helmeted head under ballistic impact agree with experimental findings independently obtained by others. The newly developed model provides a useful tool for studying injury mechanisms of BHBT and evaluating the existing standards for testing and designing combat helmets. [ABSTRACT FROM AUTHOR]

Ballistic tests with plate and stiffened targets impacted by cylindrical and blade-like projectiles were conducted using compressed gas gun to investigate the perforation-resistance performance of aero-engine fan casing during a blade-out event. It was observed that for the plate target impacted by the blade-like projectile, fragmentation on the projectile nose occurred and the targets were failed by petaling; but for the other combinations, the main failure mode of the targets was plugging and the projectiles were intact except in cases when the blade-like projectile hit the stiffeners. Due to the distinct failure mode, ballistic limit for the plate target impacted by the blade-like projectile was much higher. To analyze the perforation resistance of the target, the energy absorption modes were classified and described with analytical models. A new dishing energy calculating method was proposed for a plate normally impacted by an arbitrary cross-section projectile. The energy absorbed by each mode and the ballistic limits for the plate target were calculated using these analytical models. It was found that fragmentation of the projectile led to a larger amount of dishing energy. The formation conditions of the fragmentation on projectile nose were theoretically analyzed, and the influencing factors for the fragmentation such as the critical thickness of the target and the critical impact velocity of the projectile were derived with established formulas. The theoretical analysis agreed well with the test results. It is argued that if the target is thicker than the critical thickness and the initial velocity of the projectile is larger than the critical impact velocity, fragmentation on projectile nose will occur, failure mode of the target will change to petaling, and the perforation resistance of the target will be significantly enhanced. [ABSTRACT FROM AUTHOR]

Quasi-static tension and dynamic compression experiments on S235JR mild steel were performed using a screw-driven machine and a split Hopkinson pressure bar (SHPB) device. A wide range of strain rates from 10 −4 to 2500 s −1 has been covered during experiments. The Johnson–Cook constitutive relation was adopted to describe the material visco-plastic behaviour. Ballistic impact experiments on S235JR plates with conical-nose shaped projectile were carried out using pneumatic gas gun having different impact velocities varying from 49 to 181 m/s. A new experimental set-up allowing resistance force measurement during impact and perforation was developed. Different impact velocities and thicknesses were evaluated during ballistic experiments. All the projectiles are 12.8 mm in diameter and 28g in weight. The ballistic impact device is equipped with laser sensors for velocities measurements and piezoelectric sensors for dynamic force measurement. Based on numerical and experimental investigations, the ballistic properties and failure modes of the material have been studied. The finite element code ABAQUS/Explicit was used to simulate the perforation process but also to have a better understanding of the measurement. A good agreement between experiments and numerical results has been observed in terms of ballistic curves, failure patterns, resistance force as well as the energy balance. [ABSTRACT FROM AUTHOR]

Modeling clay is a soft malleable material made from oils and waxes. This material is fundamental for ballistic evaluation of body armors because it is used as backing material in ballistic tests. After a ballistic impact, a back-face indentation is measured to assess performance of the armor. Due to the important role of modeling clay in this particular application, its mechanical characterization and comprehension of penetration mechanics are essential for development of new personal protection systems. This paper presents a two-step computational methodology to calibrate parameters of a Cowper–Symonds material model for modeling clay at characteristic strain rates up to 1.8 × 10 4   s − 1 . In the first stage, a high-speed camera is used to record the penetration of a gas-gun launched cylindrical mass with a hemispherical cap into a block of clay. Image-processing software is used to capture the tail of the projectile as it penetrates into the clay. These data are then used to sample the penetration depth as function of time. In the second stage, an in-house developed model of penetration, based on both the spherical cavity expansion theory and the Tate penetration equation, is used to determine, by inverse analysis, the parameters of the Cowper–Symonds clay model. The proposed constitutive relationship for clay and the determined material parameters can be applied accurately to problems involving high strain rates. [ABSTRACT FROM AUTHOR]

The ballistic impact response of thermoplastic-based composite armors made from Kevlar ® fabric and polypropylene (PP) matrix has been investigated against ballistic test standard NIJ-STD 0106.01 Type IIIA. Kevlar ® fabrics of different architectures, namely 2D plain woven, 3D orthogonal and 3D angle interlock fabrics, were produced and used as reinforcements to fabricate composite armor panels, using compression molding technology. Interfacial property between PP and Kevlar ® was improved by adding a coupling agent called maleic anhydride grafted PP. Reduced density was observed in Kevlar ® thermoplastic-based composites as compared to that of the thermoset-based laminates. Ballistic impact tests were imparted with 9 mm full metal jacket (FMJ) on armor panels having different fabric architecture. Ballistic test results revealed that 2D armor was 2.4–7% more susceptible to damage than 3D armors. Hydrocode simulations were carried out using ANSYS AUTODYN v. 14.0 to obtain an estimate for the ballistic limit velocity and simulate failure modes. Post-impact damage patterns obtained from the simulations were compared with the experimental results to assess the performance of the simulations. Good correlation between the hydrocode simulations and experiments was found, both in terms of failure modes and damage patterns. 3D composite armors were able to confront the 9 mm FMJ projectile; however, the 2D plain woven armors failed. The increase in the ballistic limit from 2D plain woven armor to 3D orthogonal and 3D angle interlock armors was 16.44% and 20%, respectively, indicating the effect of fabric architecture. [ABSTRACT FROM AUTHOR]

Soft-matrix ballistic laminates (such as those composed of fibres of Ultra High Molecular-Weight Polyethylene, e.g. Dyneema ® HB26 and Spectra Shield) find extensive use as catching type armour systems. The relationship between the lay-up of these laminates with respect to the observed failure mechanisms has not been empirically investigated in the open literature, and is the subject of this work. Lay-ups are characterised by two parameters: (i) sequencing (or interply lay-up angle) θ ¯ and (ii) in-plane anisotropy β , and can be mapped on to θ ¯ – β space. Four geometries that lie at the extrema of this parameter space are designed, built and tested. Testing is through ball bearing impact on circular clamped plates. The anisotropy ( β ) is coupled to the macroscopic response of the plates, while sequencing ( θ ¯ ) is coupled to the microscopic response. Penetration velocity is strongly affected by pull-out at the boundary, and in the present study this is shown to account for two-thirds of the ballistic resistance. The results have implications for validation testing on scaled samples, predictive modelling and simulation, and armour design. [ABSTRACT FROM AUTHOR]

This paper focuses on validating a numerical modelling of woven materials subjected to ballistic impact based on experimental data. Studied impact system is a 3D warp interlock fabric (4 layers of angle interlock – through the thickness) and FSP projectile (Fragment Simulating Projectile). Numerical prediction is compared with ballistic tests on data obtained from ultra-rapid camera in two typical impact cases: no perforation and perforation. Effect of deformation rate is investigated by using both mechanical properties of yarn in static and dynamic states for numerical modelling. The numerical model using dynamic parameters shows a better prediction of impact behaviour of the 3D woven fabric than the one using static parameters. [ABSTRACT FROM AUTHOR]

A new contact algorithm is implemented for the interaction of peridynamic regime and finite elements for the effective impact fracture analysis. The region that might experience fracture is modeled using peridynamics that is a reformulated theory of continuum mechanics while the impact projectile is modeled by three-dimensional finite elements in order to exploit mutual advantages of the formulations. An inverse isoparametric mapping technique and a node-to-surface contact algorithm are customized and implemented, and a penalty method enforcing displacement constraints is then incorporated for the transient analyses using the explicit time integration. The proposed numerical technique is applied to several examples for verification and validation. Starting with examining the material behavior of a peridynamic bar, rigid-body impact is then studied for the verification of contact-impact procedure. The ballistic perforation of an impactor through a steel plate is investigated numerically. Good agreement between numerical simulations and the analytical model is observed in the analysis of the residual velocities. The physical process of perforation is captured accurately in the simulations using the proposed numerical methodology. [ABSTRACT FROM AUTHOR]

The ballistic performance of an Al alloy AA7020-T651 (AlZn4.5Mg1, 3.4335) against fragment-simulating projectiles (FSPs) is investigated at impact velocities between 900 m/s and 1500 m/s. The target plates are considered as thick regarding the ratio between the specimen thickness (40 mm) and the projectile diameter (20 mm). With increasing impact velocities, the observed failure modes of the target plates change from plugging to discing. The stress state leading to the discing formation has been described and numerically modeled by the Lagrangian approach. In order to understand the mechanisms that occur in the material under highly dynamic loadings, its mechanical, thermal and micro-structural properties are discussed. The experimental conditions (thick target, penetrator of a specific shape, high-velocity impacts) allow the authors to draw conclusions, which are complementary to those that resulted from investigations of semi-thick and thin target plates under ballistic impacts in a lower velocity range. [ABSTRACT FROM AUTHOR]