Search

Researchers use a variety of target materials, and sometimes combinations of materials, in their archaeological experiments to examine thrust‐spear or projectile penetration, impact angle, durability, and other issues involving prehistoric hunting weaponry. This variety of target materials is beneficial to archaeological science in several ways, but it may also hinder the comparison of results because many of these target materials do not necessarily share similar physical properties. Here, we assess the penetration properties of four different target materials—store‐bought meat, clay, and two types of gelatin—via static penetration tests of a modern broadhead‐tipped arrow and a stone‐tipped projectile attached to an Instron Universal Materials Tester. Our analyses of load‐deflection curves, peak load, and work energy demonstrate how the four target materials are similar in some ways but different in others, which suggests that researchers may strategically employ one or several depending on the question asked or hypothesis tested. [ABSTRACT FROM AUTHOR]

Secondary blast injuries may result from high-velocity projectile fragments which ultimately increase medical costs, reduce active work time, and decrease quality of life. The role of skin penetration requires more investigation in energy absorption and surface mechanics for implementation in computational ballistic models. High-speed ballistic penetration studies have not considered penetrating and non-penetrating biomechanical properties of the skin, including radial wave displacement, resultant surface wave speed, or projectile material influence. A helium-pressurized launcher was used to accelerate 3/8″ (9.525 mm) diameter spherical projectiles toward seventeen whole porcine legs from seven pigs (39.53 ± 7.28 kg) at projectile velocities below and above V50. Projectiles included a mix of materials: stainless steel (n = 26), Si3N4 (n = 24), and acetal plastic (n = 24). Tracker video analysis software was used to determine projectile velocity at impact from the perpendicular view and motion of the tissue displacement wave from the in-line view. Average radial wave displacement and surface wave speed were calculated for each projectile material and categorized by penetrating or non-penetrating impacts. Two-sample t-tests determined that non-penetrating projectiles resulted in significantly faster surface wave speeds in porcine skin for stainless steel (p = 0.002), plastic (p = 0.004), and Si3N4 ball bearings (p = 0.014), while ANOVA determined significant differences in radial wave displacement and surface wave speed between projectile materials. Surface wave speed was used to quantify mechanical properties of the skin including elastic modulus, shear modulus, and bulk modulus during ballistic impact, which may be implemented to simulate accurate deformation behavior in computational impact models. [ABSTRACT FROM AUTHOR]

In shooting crimes, ballistics tests are often recommended in order to reproduce the wound characteristics of the involved persons. For this purpose, several "simulants" can be used. However, despite the efforts in the research of "surrogates" in the field of forensic ballistic, the development of synthetic models needs still to be improved through a validation process based on specific real caseworks. This study has been triggered by the findings observed during the autopsy performed on two victims killed in the same shooting incident, with similar wounding characteristics; namely two retained head shots with ricochet against the interior wall of the skull; both projectiles have been recovered during the autopsies after migration in the brain parenchyma. The thickness of the different tissues and structures along the bullets trajectories as well as the incident angles between the bullets paths and the skull walls have been measured and reproduced during the assemblage of the synthetic head models. Two different types of models ("open shape" and "spherical") have been assembled using leather, polyurethane and gelatine to simulate respectively skin, bone and soft tissues. Six shots have been performed in total. The results of the models have been compared to the findings of post-mortem computed tomography (PMCT) and the autopsy findings.Out of the six shots, two perforated the models and four were retained. When the projectile was retained, the use of both models allowed reproducing the wounds characteristics observed on both victims in terms of penetration and ricochet behaviour. However, the projectiles recovered from the models showed less deformation than the bullets collected during the autopsies. The "open shape" model allowed a better controlling on the shooting parameters than the "spherical" model. Finally, the difference in bullet deformation could be caused by the choice of the bone simulant, which might under-represent either the strength or the density of the human bone. In our opinion, it would be worth to develop a new, more representative material for ballistic which simulates the human bone. [ABSTRACT FROM AUTHOR]

Current methods used in terminal ballistics to determine the volume of temporary cavities created by projectiles in soft tissue simulants (such as ballistic soap) usually involve silicone-casting to obtain the cavity moulds. However, these methods have important drawbacks including their little sensitivity and precision, besides the fact that they are destructive. Imaging techniques such as computed tomography (CT) might not only overcome those limitations but also offer useful tools for digitally reporting the scientific results. This work accomplished the 3D digital reconstruction of the cavities created by different projectiles in ballistic soap blocks. This way, the total volume of the cavities, the projectile penetration depths, and other measurements were determined, rendering better capabilities when compared to the current silicone method. All these features were achieved through the CT analysis and 3D Slicer imaging software. In addition, it is worth mentioning that the method can preserve the evidence by digitally obtaining, signing, and storing the infographic videos displaying the 3D-reconstructed cavities. [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]

Penetration and perforation performance of the rock targets by hard projectiles is suitable for understanding the ballistic behavior of the strategic and important structures such as protective structures, bunkers, ammunition stores, and nuclear power plants that are sensitive to missile impacts. In this study, ballistic penetration tests and numerical simulations were performed to examine the behavior of geo-material targets against hard projectile impacts. The granitic rock plates were used as target materials, and the projectiles were made of hardened 4340 steel. A loading-rate dependent shear failure model was suggested based on experimental data andimplemented into LS-DYNA using a usermaterial subroutine. The ballistic test results were used to validate the suggested model. The numerical ballistic data simulated experimental behaviors relatively well. [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 • 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]

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]

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]

Molecular dynamics simulations of the ballistic Taylor test are used to explore correlation between the largest fragment mass and the impact energy of a projectile as well as a set of selected state variables. Flat-ended, monocrystalline, nanoscale bars collide with a rigid wall with striking velocities ranging from 0.27 km/s to 60 km/s. The investigation emphasis is on two border regions of the emerging nonlinear phenomenological model identified with two transitions: the damage-fragmentation transition and the shattering transition. In between these two nonlinear regions, the maximum fragment mass is largely inversely proportional to the impact energy, and the maximum values of the pressure, temperature, and the square of the effective strain. A reverse-sigmoid phenomenological model is proposed to capture the unifying features of this nonlinear and saturable dependence. A crystallographic orientation dependence of the damage-fragmentation transition parameters is investigated. [ABSTRACT FROM AUTHOR]

Analytical formulas for calculating the maximum velocity of penetration of doublelayer cermet and ceramic/organic-plastic targets are obtained taking into account the structural characteristics of the target and the physical and mechanical properties of the projectile and target materials. Using these formulas, the ballistic resistance of targets was studied and the possibility of optimizing their structure was shown. The results agree qualitatively with available experimental data. The optimal relative thickness of the ceramic layer which provides maximum penetration velocity was determined at areal densities of the target of 30-50 kg/m for different substrate materials. It is found that these velocity values depend weakly on the areal density of the target and are mainly determined by the properties of the substrate material. [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]

Interior ballistics analysis is required for the development of the gun system. Interior ballistics is a complex phenomenon containing the propellant combustion and gas flow and is completed in tens of milliseconds during gun firing. Thus, some data cannot be directly measured by experiment. Numerical analysis is therefore traditionally used to understand the complex gun firing phenomena. In previous studies, the two-dimensional axisymmetric numerical method for interior ballistics using the Eulerian-Lagrangian approach has been developed. There are some limits in depicting the actual phenomena with two-dimensional models. Therefore, a three-dimensional numerical model has been built in the present study. Unlike the conventional method, the calculation has been conducted by separating the physical phenomena into the combustion part and the flow part for simplicity and efficiency. The internal flow in the gun barrel has been calculated by using the STAR-CCM+ and the source terms produced by the propellant combustion has been computed by utilizing the existing code. The developed numerical model has been compared with the AGARD gun results and the simulation of 40 mm gun firings. The reliability of the developed model has been confirmed because the results of the numerical analysis greatly agree with the simulation results. The basis of the three-dimensional analysis of the interior ballistics has been formed through this study. [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 subject of the paper is a description of a simple test from the field of terminal ballistics and the handling of issues arising during its simulation using the numerical techniques of the finite element method. With regard to the possible excessive reshaping of the finite element mesh there is a danger that problems will arise such as the locking of elements or the appearance of negative volumes. It is often necessary to introduce numerical extensions so that the simulations can be carried out at all. When examining local damage to structures, such as the penetration of the outer shell or its perforation, it is almost essential to introduce the numerical erosion of elements into the simulations. However, when using numerical erosion, the dissipation of matter and energy from the computational model occurs in the mathematical background to the calculation. It is a phenomenon which can reveal itself in the final result when a discrepancy appears between the simulations and the experiments. This issue can be solved by transforming the eroded elements into smoothed particle hydrodynamics particles. These newly created particles can then assume the characteristics of the original elements and preserve the matter and energy of the numerical model. [ABSTRACT FROM AUTHOR]

The mechanisms of progressive penetration for two ultrahigh molecular weight polyethylene (UHMWPE) reinforced laminates have been investigated. One used an UHMWPE fiber reinforcement while the other utilized molecularly aligned tape. Both materials had similar out of plane compressive strengths, but the fiber system had a 40% higher in plane tensile strength than the tape. Laminated, 6 mm thick plates with a [0°/90°] ply architecture were impacted by a 12.7 mm diameter sphere under conditions that either allowed out of plane plate deflection or eliminated this deflection by rear support of the target. The depth of penetration and the ballistic limit in the rear-supported tests were identical for the two materials, and proceeded by progressive ply failure. However, tests in the edge clamped condition resulted in a substantially higher penetration resistance, especially for the higher tensile strength fiber-reinforced material. Edge clamped testing of a bilayer target, where the front third was composed of the tape material and the remainder comprised fiber reinforced laminate, had the same ballistic limit as a target composed of only the higher ply tensile strength fiber reinforced material. Penetration in both test support conditions was discovered to occur by tensile ply rupture under the projectile, consistent with a recently proposed mechanism for converting out of plane compression to in plane ply tension. Lateral displacement of plies was also observed near the sides of impact craters in both materials, indicating the existence of a second mechanism impeding penetration of the spherical shaped projectile. [ABSTRACT FROM AUTHOR]

In practical forensic casework, backspatter recovered from shooters' hands can be an indicator of self-inflicted gunshot wounds to the head. In such cases, backspatter retrieved from inside the barrel indicates that the weapon found at the death scene was involved in causing the injury to the head. However, systematic research on the aspects conditioning presence, amount and specific patterns of backspatter is lacking so far. Herein, a new concept of backspatter investigation is presented, comprising staining technique, weapon and target medium: the 'triple contrast method' was developed, tested and is introduced for experimental backspatter analysis. First, mixtures of various proportions of acrylic paint for optical detection, barium sulphate for radiocontrast imaging in computed tomography and fresh human blood for PCR-based DNA profiling were generated (triple mixture) and tested for DNA quantification and short tandem repeat (STR) typing success. All tested mixtures yielded sufficient DNA that produced full STR profiles suitable for forensic identification. Then, for backspatter analysis, sealed foil bags containing the triple mixture were attached to plastic bottles filled with 10 % ballistic gelatine and covered by a 2-3-mm layer of silicone. To simulate backspatter, close contact shots were fired at these models. Endoscopy of the barrel inside revealed coloured backspatter containing typable DNA and radiographic imaging showed a contrasted bullet path in the gelatine. Cross sections of the gelatine core exhibited cracks and fissures stained by the acrylic paint facilitating wound ballistic analysis. [ABSTRACT FROM AUTHOR]

A new penetration equation for ballistic limit analysis (BLA) of a projectile–target pair is developed and presented. A critical review of the classic BLA (CBLA) has identified that the CBLA penetration equations do not satisfy the conservation of momentum and energy principles simultaneously and completely. It has also been found that the classic definition of residual velocity of the projectile does not quantify the instantaneous rigid body velocity of the projectile at ballistic limit. A new definition of the projectile relative velocity with respect to the target in contact (and in motion) is defined, and this new definition is used to define the projectile instantaneous velocity at ballistic limit. With this new definition of the projectile instantaneous velocity, the new penetration equation is derived satisfying both the conservation of momentum and energy principles simultaneously. A general functional form of the new penetration equation is used in analyzing experimental data and the results are found to match well with the experiments. The new equation is shown to be able to explain projectile residual velocity at and around ballistic limit, can predict the jump velocity at ballistic limit (if any), and is applicable to experimental ballistic data of a wide range of thin and thick targets. The present work sets the background for further development of theoretical penetration models incorporating material properties and parameters of the projectile–target pair. [ABSTRACT FROM PUBLISHER]

• 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]

Ballistic performance of an armour steel at different tempering conditions against a tungsten heavy alloy long rod kinetic energy projectile has been investigated. The ballistic performance was found to increase with decreasing tempering temperature but the performance increments were not proportional to the strength increase caused by the tempering. Both target and projectile underwent fragmentation at the penetration interface in all the three targets. Apart from the strength target material deformation behaviour also showed considerable influence on ballistic performance. The ballistic performance appears to increase with decreasing toughness for a given strength. [ABSTRACT FROM AUTHOR]

The database for depth of penetration by projectiles into semi-infinite targets is quite extensive. The objective is to use the experimental semi-infinite penetration data to predict finite-thickness target effects. Similitude considerations are used to represent penetration response as a function of a normalized impact velocity, which is the ratio of the penetration pressure to the target strength. Then, a least-squares regression analysis methodology was applied to the normalized experimental data to provide an analytic expression for the normalized depth of penetration as a function of the normalized impact velocity over a very large velocity range, typically a few hundred meters per second to over 3500 m/s. We use the analytic expression, along with some simplifying assumptions, to estimate ballistic limit thickness T 50 and/or the ballistic limit velocity V 50 . If a target is overmatched, i.e., perforated by the projectile, an estimate is also made for the projectile residual velocity and residual length. The experimental data on which the regression fit is based consists of L / D 10 projectiles, so a procedure is also developed to account for different projectile aspect ratios. A series of examples are provided to demonstrate the utility and accuracy of the approach. [ABSTRACT FROM AUTHOR]

In this study, the penetration of tungsten projectile into the composite ceramics - metal target is stimulated using Autodyn software. The behavioral equation used in this simulation is Johnson Cook for projectile and metal and Johnson Holmquist for ceramic. Also, the equation of state used in tungsten projectile and metal is linear and in ceramic layer is Polynomial. In each model the output speed of the projectile is calculated and compared with the results of experimental tests. The results obtained indicate a good agreement between performed simulation and experimental results. Then Kevlar-epoxy and glass-epoxy polymer layer add to the ceramic/aluminum target and projectile penetration resistance is investigated. [ABSTRACT FROM AUTHOR]

Polymer composites comprising ultra-high molecular weight polyethylene (UHWMPE) fibers in a compliant matrix are now widely used in ballistic applications with varying levels of success. This is primarily due to a poor understanding of the mechanics of penetration of these composites in ballistic protection systems. In this study, we report experimental observations of the penetration mechanisms in four model systems impacted by a 12.7 mm diameter spherical steel projectile. The four model targets designed to highlight different penetration mechanisms in Dyneema ® UHWMPE composites were: (i) a bare aluminum plate; (ii) the same plate fully encased in a 5.9 mm thick casing of Dyneema ® ; (iii) the fully encased plate with a portion of the Dyneema ® removed from the front face so that the projectile impacts directly the Al plate; and (iv) the fully encased plate with a portion of the Dyneema ® removed from the rear face so that the projectile can exit the Al plate without again interacting with the Dyneema ® . A combination of synchronized high speed photography with three cameras, together with post-test examination of the targets via X-ray tomography and optical microscopy was used to elucidate the deformation and perforation mechanisms. The measurements show that the ballistic resistance of these targets increases in the order: bare Al plate, rear face cutout target, fully encased target and front face cutout target. These findings are explained based on the following key findings: (a) the ballistic performance of Dyneema ® plates supported on a foundation is inferior to Dyneema ® plates supported along their edges; (b) the apparent ballistic resistance of Dyneema ® plates increases if the plates are given an initial velocity prior to the impact by the projectile, thereby reducing the relative velocity between the Dyneema ® plate and projectile; and (c) when the projectile is fragmented prior to impact, the spatially and temporally distributed loading enhances the ballistic resistance of the Dyneema ® . The simple model targets designed here have elucidated mechanisms by which Dyneema ® functions in multi-material structures. [ABSTRACT FROM AUTHOR]

In this research, quasi-static penetration and ballistic properties of non-woven kenaf fibres/Kevlar epoxy hybrid laminates with thicknesses ranging from 3.1 mm to 10.8 mm by hard projectile at normal incidence have been experimentally investigated. Hybrid composites were fabricated by hand lay-up technique in a mould and cured at room temperature for 24 h by static load. Hybrid composites consist of Kevlar layers and non-woven kenaf layers at three different configurations, i.e. kenaf at the innermost layers, outermost layers and at the alternating layers. Kevlar/epoxy and kenaf/epoxy composites were also fabricated for comparison purpose. Quasi-static experiments were conducted using a tensile testing machine at the speed of 1.27 mm/min and 2.54 mm/min. Ballistic tests were conducted using 9 mm full metal jacket bullet using a powder gun at speeds varying from 172 to 339 m/s, with the initial and a residual velocity of the projectiles is measured. The tested sample was carefully examined with respect to failure modes. Results showed the effect of hybridization in term of force-displacement curves, energy dissipation and damage mechanisms for quasi-static test. Maximum force to initiate penetration is higher in hybrid composites compared to kenaf/epoxy and Kevlar/epoxy composites. Hybridization of kenaf-Kevlar resulted in a positive effect in terms of energy absorbed (penetration) and maximum load. In the case of ballistic tests, hybrid composites recorded lower ballistic limit (V50) and energy absorption than the Kevlar/epoxy composite. The V50 of hybrid composites with kenaf at the outermost layers is superior to other hybrid composites. These finding inspired further exploration of hybrid composite for ballistic armour spall-liner application. [ABSTRACT FROM AUTHOR]

Studies of ballistic penetration into metal plates and their numerical simulation currently play a vital role in the defence sector. However, no congruent results have been presented so far, especially when it comes to impact on welded plates. Furthermore, these issues are investigated for normal impacts and very few have made an attempt for oblique impacts. Thus the aim of the present work is to conduct numerical simulation using Abaqus/Explicit in order to evaluate the ballistic performance of similar and dissimilar welded plates subjected to various bullet velocities and impact angles. The effect of post weld residual stresses and associated plastic damage on the ballistic performance of similar (Al6061) and dissimilar (Al 6061- SS 304) welded plates is also determined. The energy absorbed by the welded plates for various configurations was determined and the results are critically evaluated. [ABSTRACT FROM AUTHOR]

The article presents an experimental and numerical approach to estimate ballistic limits of handgun hollow point bullet Action 5 penetrating the target representing a transport airplane fuselage and a forward obstacle. The target containing the composite sidewall, the insulation glass wool layer and the duralumin skin plate is perforated in two combinations -- directly and using forward obstacle in form of ballistic gel as substitute biological material to achieve the conditions o f firing on-board by Air Marshals, for instance. The ballistic resistance of the fuselage structure fired directly is very poor and in case of firing the gel block first is limited to some extend due to expansion ability of the bullet. The simulation using Finite Element Method system Ansys Autodyn v.14 introduces 2D model presenting the estimation of the ballistic limit inform of gel block thickness for particular combinations of the target based on experiments. [ABSTRACT FROM AUTHOR]

Abstract: We have used forward ballistic, reverse ballistic and computational analysis techniques to interrogate the effect of the gilding jacket from a 7.62 mm × 51 mm FFV armour-piercing bullet during the penetration of ceramic-faced targets. When the gilding jacket is removed, it is shown that greater damage occurs to the core suggesting that the presence of the jacket is pre-damaging the ceramic before core arrival. This is confirmed through computational analysis. This work highlights possibilities in enhancing protection by pre-stripping the bullet''s jacket prior to ceramic impact. [Copyright &y& Elsevier]

Abstract: The spherical cavity expansion theory is applied. Considered are the effects of the resistance of the projectile nose and the friction of the projectile shank on the penetration depths and residual velocities of the projectiles. By progressively increasing the depth of penetration into double-layered composite targets, we adopted numerical calculation manner to develop the analytical model that determined the residual velocities, ballistic limit velocities, and penetration depths of the ogival nose projectiles during normal impact with double-layered composite targets of varying thicknesses. We also used NATO 0.30″ armor piercing (AP) bullets to strike double-layered composite targets made from 6061-T651 aluminum, 5083-H116 aluminum, polycarbonate (PC), and polymethylmethacrylate (PMMA) plates for the ballistic tests. The analytical model predictions show well agreement with experimental results from Dey et al. (Int. J. Solids Struct. 44 (2007) 6701–6723.), Børvik et al. (Proceedings of the SEM Annual Conference, 2009), and the present ballistic tests. [Copyright &y& Elsevier]

A combined theoretical–semiempirical penetration model of ballistic penetration of thick section composites has been developed. The penetration model is developed by breaking down the penetration event into two major phases, that is, (i) the short-time phase I shock compression and (ii) the long-time phase II dynamic penetration. Phase I shock compression considers a one-dimensional stress wave propagation theory and the rate effects on material properties. On the other hand, the phase II dynamic penetration phase incorporates a dynamic increase factor to a semiempirical quasi-static penetration resistance curve. The combined theoretical–semiempirical penetration model is compared with finite element analyses of the same problem and good correlations are obtained. [ABSTRACT FROM AUTHOR]

Abstract: This paper discusses the technique of Digital Speckle Radiography (DSR) and its application to the measurement of the internal flow fields in penetration of sand by long-rod projectiles at velocities up to 200 m/s. Three different rod nose shapes were studied: flat-ended, ogive-2, and hemispherical. Impacts performed on gelatine and concrete gave significantly different displacement fields to sand. Sand, therefore, cannot either be modelled as a fluid or as a conventional solid. Simulations performed using a code written by two of the authors (Bobaru and Promratana) showed that the velocity distribution has a very different appearance to the force distribution. This suggests that processes such as reorganisation, sliding and void filling take place, allowing the grains to move in directions other than the applied force. The resulting velocity distribution bears a strong resemblance to the experimentally measured displacement fields. [Copyright &y& Elsevier]

Abstract: Reverse ballistic experiments were used to investigate confinement, pre-damaged and intact, and rod size effects on penetration of long, gold rods into silicon carbide (SiC-N). Rod diameters were 1.0mm and 0.75mm, and lengths were 70mm and 50mm, respectively. Within data scatter, penetration velocity was the same for intact (bare or sleeved), pre-damaged (thermally shocked with non-contiguous cracks), and in situ comminuted SiC-N. Penetration velocity was independent of rod diameter within the data scatter. An expression for the penetration velocity versus impact velocity is found using linear regression. It is proposed that the reason there is no difference in the penetration rate between intact and pre-damaged (failed) SiC is because, after the first few microseconds following impact, the rod penetrates failed material in both cases. [Copyright &y& Elsevier]

Glass impact experiments were designed at three different scales-0.22-cal, 0.375-cal, and 0.50-cal-named after the diameter of the bullets. Four experimental series were conducted at the three scale sizes: (1) Lexan®-only experiments; (2) monoblock glass experiments; (3) single impact bonded glass experiments, and (4) multi-hit experiments. The experiments were conducted to obtain residual velocity Vr as a function of impact (striking) velocity Vs, including sufficient partial penetrations to calculate a ballistic limit velocity V50. The Vs - Vr data were fit to the Lambert equation to obtain another estimate of V50. The objective of the experiments was to investigate whether a time dependency exists in glass damage/failure for ballistic experiments, and if so, quantify this dependence. No scale effect was observed in experimental results for the Lexan®-only experiments. But a variety of scale effects were observed in the glass impact experiments, suggesting that failure is time dependent within the timeframe of ballistic events [ABSTRACT FROM AUTHOR]

Numerical studies were conducted on the ballistic performance of alumina ceramic (AD95) tiles based on depth of penetration method, when subjected to normal impact of tungsten long rod projectiles at velocities ranging from 1100 to 2000 ms-1. The residual depth on after-effect target was derived in each case, and the ballistic efficiency factor was determined using the corresponding penetration depth on medium carbon steel. Anti-penetration experiment study of the AD95 ceramic tiles to tungsten long rod projectiles has been carried out to verify the accuracy of numerical simulation model. The result shows that numerical simulation results agree well with the corresponding experiment results and AD95 ceramic has excellent ballistic performance than medium carbon steel. The ballistic efficiency factor increases with velocity increasing when impact velocity lower than 1300 ms-1, and when it was higher than 1300 ms-1 the ballistic efficiency factor has almost no difference. [ABSTRACT FROM AUTHOR]

Transport properties of open chaotic ballistic systems and their statistics can be expressed in terms of the scattering matrix connecting incoming and outgoing wave functions. Here we calculate the dependence of correlation functions of arbitrarily many pairs of scattering matrices at different energies on the Ehrenfest time using trajectory-based semiclassical methods. This enables us to verify the prediction from effective random-matrix theory that one part of the correlation function obtains an exponential damping depending on the Ehrenfest time, while also allowing us to obtain the additional contribution that arises from bands of always correlated trajectories. The resulting Ehrenfest-time dependence, responsible, e.g., for secondary gaps in the density of states of Andreev billiards, can also be seen to have strong effects on other transport quantities, such as the distribution of delay times. [ABSTRACT FROM AUTHOR]

The spin transfer torque in an all-metal dual spin valve, in which two antiparallel-aligned pinned ferromagnetic layers are on the two sides of a free ferromagnetic layer with two thin normal metal spacers in between, is studied in the ballistic regime. It is argued that, similar to the results in the diffusive regime, the spin transfer torque is dramatically enhanced in comparison to that in a conventional spin valve in the ballistic regime. Within the Slonczewski approach, an analytical expression of the torque on the free magnetic layer is obtained, which may serve as a theoretical model for the micromagnetic simulation of the spin dynamics in a dual spin valve. Depending on the orientation of the free layer and the degree of electron polarization, the spin transfer torque enhancement could be tenfold. The general cases when transmission and reflection probabilities of the free layer are different from zero or one are also numerically calculated. [ABSTRACT FROM AUTHOR]

Abstract: Impact, damage evolution and penetration of thick-section composites are investigated using explicit finite element (FE) analysis. A full 3D FE model of impact on thick-section composites is developed. The analysis includes initiation and progressive damage of the composite during impact and penetration over a wide range of impact velocities, i.e., from 50 m/s to 1000 m/s. Low velocity impact damage is modeled using a set of computational parameters determined through parametric simulation of quasi-static punch shear experiments. At intermediate and high impact velocities, complete penetration of the composite plate is predicted with higher residual velocities than experiments. This observation revealed that the penetration-erosion phenomenology is a function of post-damage material softening parameters, strain rate dependent parameters and erosion strain parameters. With the correct choice of these parameters, the finite element model accurately correlates with ballistic impact experiments. The validated FE model is then used to generate the time history of projectile velocity, displacement and penetration resistance force. Based on the experimental and computational results, the impact and penetration process is divided into two phases, i.e., short time Phase I – shock compression, and long time Phase II – penetration. Detailed damage and penetration mechanisms during these phases are presented. [Copyright &y& Elsevier]