Ballistic Panels Research Articles

Mechanically Strong Polymer Sheets from Aligned Ultrahigh-Molecular-Weight Polyethylene Nanocomposites.

Ultrahigh-molecular-weight polyethylene (UHMWPE) is of great interest as a next-generation body armor material because of its superior mechanical properties. However, such unique properties depend critically on its microscopic structure characteristics, including the degree of crystallinity, chain alignment, and morphology. Here, we present a highly aligned UHMWPE and its composite sheets containing uniformly dispersed boron nitride (BN) nanosheets. The dispersion of BN nanosheets into the UHMWPE matrix increases its mechanical properties over a broad temperature range. Experiments and simulation confirm that the alignment of chain segments in the composite matrix increases with temperature, leading to an improvement in mechanical properties at high temperature. Together with the large thermal conductivity of UHMWPE and BN, our findings serve to expand the application spectrum of highly aligned polymer nanocomposite materials for ballistic panels and body armor over a broad range of temperatures.

Assessing through-thickness damage propagation, impact tests on layered composite beams - experimental work and numerical simulation

The growing applications of layered fiber reinforced composite materials lead to the potential use of such lightweight materials for blast and ballistic impact resistant panels. Under such high strain rate loading, through-thickness damage propagation is crucial for the structural integrity of the panels. Experiments performed in composite panels under blast loading exhibited little information for the understanding of the time-line of damage propagation as only post-mortem inspection can be done. Instrumentation may be installed in order to follow the blast but the task reveals itself arduous as all the instruments must be protected against the blast. The sparse information can be valuable for configuration screening purposes, but is not su ffi cient for comparison and validation of numerical models. The work focuses on performing controlled impact experiments in narrow beams filmed side-wise with high-speed cameras. The narrow geometry of the beams leaves the thickness of the specimen exposed to the cameras allowing for a real-time monitoring of the stress waves propagating and for assessing the time-line of through-thickness damage propagation onset. Results showed that polyethylene impactors, given the right diameter, are the most suitable soft impactors. Numerical models including in-plane and out-of-plane damage propagation are being built in order to replicate the experimentally observed damage. The ultimate goal being establishing design rules for such lightweight fiber reinforced panels. It is numerically observed that, the speed propagation of delamination in the longitudinal direction reaches a common constant value for all interfaces.

Hybrid panels from woven Kevlar® and Dyneema® fabrics against ballistic impact with wearing flexibility

.This paper reports on a study of hybrid ballistic panels consisting of plain-woven fabrics made from Kevlar® and Dyneema®, aiming to achieve protective and flexible ballistic panels. Experimental and numerical approaches were adopted for this research. Ballistic penetration tests indicated that the single-phase Kevlar® fabric panels was more energy absorbent than that of the Dyneema® fabric panels at low areal density. When the areal density reached around 1.4 kg/m2, the Kevlar® woven fabric panels started to outperform the Dyneema® counterpart in terms of energy absorption. Accordingly, hybrid panels from the two types of fabrics were engineered and such panels were associated to the higher specific energy absorption than the single-phase panels. It was also found that placing the Kevlar® fabric layer close to the impact face and the Dyneema® fabric layers towards the back face resulted in an improvement of around 16% in ballistic performance over the panels constructed in the reverse sequence. In this investigation, the optimum ratio of the two types of fabrics in hybrid panels was found to be 1:1.

Stabbing resistance of body armour panels impregnated with shear thickening fluid

This paper presents an investigation on the use of shear thickening fluid (STF) to improve stabbing resistance of soft ballistic body armour. STFs were produced from polyethylene glycol and silica nanoparticles. The effects of silica nanoparticle sizes and silica nanoparticle weight fraction were studied and STFs made with the different compositions were used to impregnate the Twaron® woven fabrics. Systemic investigations into rheological behaviour of STF were carried out experimentally on STFs with different compositions. STF impregnated woven fabric panels were created and tested for stabbing resistance. Stabbing impact tests were conducted on 6 different types of STF impregnated fabric panels against 2 untreated fabric panels, and the results were studied against the benchmark fabrics without STF impregnation. Based on the same number of layers of fabric, the STF impregnation improves the stabbing resistance notably. For same panel areal density, the STF impregnated panels outperform the untreated fabric panel. The results of this research indicate the possibility of lighter ballistic panel materials for higher stabbing protection. It was also found that higher nanoparticle weight fraction and larger nanoparticle size of silica leads to better stabbing resistance performance among the STF impregnated panels.

Analytical investigation of high-velocity impact on hybrid unidirectional/woven composite panels

In addition to fiber properties, the fabric structure plays an important role in determining ballistic performance of composite body armor textile. Textile structures used in ballistic protection are woven fabrics, unidirectional (UD) fabric structures, and nonwoven fabrics. In this article, an analytical model based on wave propagation and energy balance between the projectile and the target is developed to analyze hybrid fabric panels for ballistic protection. The hybrid panel consists of two types of structure: woven fabrics as the front layers and UD material as the rear layers. The model considers different cross sections of surface of the target in the woven and UD fabric of the hybrid panel. Also the model takes into account possible shear failure by using shear strength together with maximum tensile strain as the failure criteria. Reflections of deformation waves at interface between the layers and also the crimp of the yarn are modeled in the woven part of the hybrid panel. The results show greater efficiency of woven fibers in front layers (more shear resistance) and UD yarns in the rear layers (more tensile resistance), leading to better ballistic performance. Also modeling the yarn crimp results in more trauma at the backface of the panel producing data closer to the experimental results. It was found that there is an optimum ratio of woven to UD materials in the hybrid ballistic panel.

Study of energy absorption and failure modes of constituent layers in body armour panels

Abstract This study aims to investigate ballistic resistant efficiency of individual layers in body armour panels in order to further understand the energy absorption and failure modes of the layers and the panel. Finite Element (FE) analysis, in conjunction of experimental methods, was used to quantify the ballistic responses of the individual layers under ballistic impact. Perforated and non-perforated ballistic tests and photographic morphology examination were employed in this study for layer and panel failure mechanisms. The results of the investigation revealed that the fabric layers at different positions in the panel exhibit different transverse deformation and stress distribution. In the perforated panel, energy absorption in each layer increases gradually from the front to the rear of the panel. Comparison with the stand-alone fabric layer revealed that the energy absorption efficiency of the front layers is lower than that of the rear for the perforated panels. Based on the failure modes of different fabric layers in a ballistic panel, it is possible that the construction of the panel be optimised for improved ballistic performance.

Microscale groove effect on shear strength of epoxy-bonded dissimilar metal plate

In this study, the shear strengths of Al 7075–HSS adhesive bonded, grooved and smooth plates were investigated. The proven toughness and durability of adhesives have drawn the attention of researchers who want to take advantage of the technology to benefit the development of ballistic resistance sandwich panels. However, the strength of the panel depends on the design of surface topography. Therefore, it is essential to understand the fracture upon loading parallel to the plane of the adhesive bonded metal plates. In this experiment, toughened epoxy was used to bond dissimilar metal plates at 1 mm thickness. The shear tests were performed with a universal-testing machine to identify the maximum fracture loads. The results showed that a shear lap joint specimen with a grooved surface yields a higher strength than a smooth specimen. From the fracture behaviour of all specimens, interfacial failure with some degree of cohesive failure was observed. This indicates that the strength of the adhesive-bonded metal plate driven by a mechanical interlocking effect and mode of failure for thick bondline was the result of interfacial strength rather than adhesive bulk strength. Shear value results and fractography for 1 mm bond thickness provide insights towards steel fibre application in epoxy.

Экспериментальная оценка ударной прочности слоистых композитов с термопластичной матрицей

Tensile tests were performed to obtain the quasi-static mechanical properties of the aramid fabrics (Twaron®, RUSLAN®-SVM). The elastic modulus of filaments, pulled out from the fabrics was measured with compact testing machine INSTRON 5942. Filaments pull-out tests were carried out to compare the frictional forces in different aramid fabrics. Eight various types of ballistic panels with the thermoplastic matrix based on polyethylene were fabricated and two types ballistic panels based on UHMPE (Dyneema®). Extensive ballistic tests have been carried out on various ballistic panels using 6.35 mm steel ball. Special powder gun stand for acceleration of projectiles with terminal velocity up to 900 m/s was developed The ballistic performance was assessed in terms V50 threshold as well as post V50 limit. After the test, the comparison was produced of effectiveness between all of materials used in this work. Laminates based on UHMPE fibers are much better than others in respect to the values of on indicators of V50 (about 10 %) and of the absorbed energy (about 25 %) under high-velocity impact conditions. But their energy absorption capability can sharply drop down when projectile's velocity exceeds the ballistic limit. When selecting reinforcing aramid fabric for ballistic application, it is important to consider not only the mechanical properties of the fibers and the type of fabric construction, but also the material should have good results on all parameters of ballistic efficiency such as filaments width, etc. Best aramid fabric composite was SVM S125 with twill construction and LDPE films.

Numerical and experimental investigations into ballistic performance of hybrid fabric panels

Strong, low density fibres have been favoured materials for ballistic protection, but the choice of fibres is limited for making body armour that is both protective and lightweight. In addition to developments of improved fibres, alternative approaches are required for creating more protective and lighter body armour. This paper reports on a study on hybrid fabric panels for ballistic protection. The Finite Element (FE) method was used to predict the response of different layers of fabric in a twelve-layer fabric model upon impact. It was found that the front layers of fabric are more likely to be broken in shear, and the rear layers of fabric tend to fail in tension. This suggested that using shear resistant materials for the front layer and tensile resistant materials for the rear layer may improve the ballistic performance of fabric panels. Two types of structure, ultra-high-molecular-weight polyethylene (UHMWPE) woven and unidirectional (UD) materials, were analyzed for their failure mode and response upon ballistic impact by using both FE and experimental methods. It was found that woven structures exhibit better shear resistance and UD structures gives better tensile resistance and wider transverse deflection upon ballistic impact. Two types of hybrid ballistic panels were designed from the fabrics. The experimental results showed that placing woven fabrics close to the impact face and UD material as the rear layers led to better ballistic performance than the panel constructed in the reverse sequence. It has also been found that the optimum ratio of woven to UD materials in the hybrid ballistic panel was 1:3. The improvement in ballistic protection of the hybrid fabric panels allows less material to be used, leading to lighter weight body armour.

Engineering and analysis of gripping fabrics for improved ballistic performance

Previous studies show that fabric construction is one of the key factors affecting the performance of ballistic fabrics. In order to investigate the effect of yarn gripping in fabrics, plain woven narrow fabrics with different widths have been designed and studied. In terms of narrow fabrics, it was found that narrower fabric demonstrates better performance than wider ones under low impact energy due to the better weft yarn gripping effect of the selvages. In the case of higher impact energy, wider narrow fabric shows better ballistic performance in having sufficient material to dissipate the impact energy. Different ballistic panels were made for ballistic testing, with each panel only formed from the same fabric. Performance of narrow fabric panels is disappointing compared to the broad fabric panel due to the discontinuity of the fabric material. A novel broad fabric has been engineered providing both enhanced yarn gripping and material continuity. Tests showed that panels made from such fabrics have improved performance against both back face deformation and projectile penetration.

Body Armor Technology: A Review of Materials, Construction Techniques and Enhancement of Ballistic Energy Absorption

Body armor is a material to protect body from injury of various kind of high speed projectile impact velocity in combat or other dangerous situation. Researchers were found to actively research and exploring new body armor technology due to the invention of new firearms. Furthermore, they were also competing in developing ballistic panel which is lighter in weight, more flexible and comfort in use, cheaper in cost and manufacturability. This paper reviews the body armor commercial and current development materials, structure and construction techniques involved and related works on enhancing ballistic energy absorption.

A Composite Consisting of a Set of Hexagonal Ceramic Bars - The Numerical Study of the Ballistic Resistance

The paper presents a numerical study of a double layer composite panels impacted by a AP (Armor Piercing) 51WC projectile. The standard panel is built with aluminum and Al2O3 ceramic continuum layers while the studied model consists of the same aluminum plate but the front one is built with a set of hexagonal ceramic bars. The bar width and the impact position influence on the ballistic resistance are analyzed and compared with the reference solution. The problem has been solved with the usage of the modeling and simulation methods as well as finite elements method implemented in LS-DYNA software. Space discretization for each option was built by three dimension elements guarantying satisfying accuracy of the calculations. For material behavior simulation specific models including the influence of the strain rate and temperature changes were considered. Projectile Tungsten Curbide and aluminum plate material were described by Johnson-Cook model and ceramic target by Johnson-Holmquist model. In the studied panels the area surrounding back edges was supported by a rigid wall. The obtained results show interesting properties of the examined structures considering their ballistic resistance. All tests has given clear results about ballistic protection panel response under WC projectile impact. Panels consisting of sets of hexagonal ceramic bars are slightly easier to penetrate, reference model is stronger by 19% for smaller bars and by only 7% for bigger rods. Despite this fact, the ceramic layer is much less susceptible to overall destruction what makes it more applicable for the armor usage. Furthermore, little influence of the projectile impact point and consequently a part of the bar which is first destroyed is proved.

Effect of artificial perspiration and cleaning chemicals on the mechanical and chemical properties of ballistic materials

AbstractDuring routine field use of soft body armor, the ballistic panels become saturated with perspiration. This condition motivates the user to clean and/or deodorize the armor, and anecdotal evidence is given for various methods used to accomplish this. Although the cleaning/deodorization is usually performed on the armor liners and coverings, there is concern that the chemicals could seep into the ballistic panels and damage the fibers. The purpose of this study was to assess the effect of artificial perspiration and cleaning chemicals on the mechanical and chemical properties of aramid, poly(p‐phenylene benzobisoxazole), and ultrahigh‐molecular‐weight polyethylene yarns after controlled cycles of exposure to artificial perspiration and dilute solutions of common cleaning chemicals. It was observed that the effect of the artificial perspiration on the properties of all of the materials tested was the same as that of water alone. Of all of the cleaning chemicals used, only chlorine bleach had a detrimental effect on the yarn properties. All other cleaning chemicals had the same effect as water alone. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

The method of neutron imaging as a tool for the study of the dynamics of water movement in wet aramid-based ballistic body armour panels

A new non-destructive method based on neutron imaging (neutron radiography) to determine the exact water content in aramid-based soft body armour panels is presented. While investigating the ballistic resistance of aramid-based body armour panels under a wet condition, it is important to precisely determine their water content and its chronological development. Using the presented method, the influence of water amount and location on impact testing as well as its time dependence was shown. In the ballistic panels used, spreading of water strongly depended on the kind of quilting. Very fast water migration could be observed when the panels were held vertically. Some first results regarding the water distribution in wet panels immediately after the impact are presented. On the basis of the presented results, requirements for a standard for testing the performance of ballistic panels in the wet state are deduced.

Ballistic resistance of body armour testing

This work is a basic presentation of NIJ 0101.04 (National Institute of Justice) standard, -whose purpose is to establish minimum performance requirements and methods of testing ballistic resistance of body armor intended to protect the torso against gunfire. This standard is a revision of NIJ Standard 0101.03 dated April 1987 and it clarifies the labeling requirements, acceptance criteria, and backface signature measurement procedure. The scope of this standard is limited only to ballistic resistance; and it does not include threats from knives and sharply pointed instruments. In addition, the standard does not include armor that incorporates inserts, or variations in construction of the ballistic panel over small areas of the torso, used for increasing the basic level of protection of the armor (whether ballistic or blunt trauma) on localized areas. .

Heat as a Factor in the Penetration of Cloth Ballistic Panels by 0.22 Caliber Projectiles

This report explores the possibility that heat plays a role in the penetration of cloth ballistic panels by 0.22 caliber projectiles. We postulate that heat is generated by friction between the surface of the projectile and the yarns, between yarns, and between filaments within a yarn in advance of and in the path of the projectile. Evaluations by light microscopy, polarized light microscopy, and scanning electron microscopy show heat- induced damage in fibers in the path of and several layers preceding the layer at which a 0.22 caliber projectile comes to rest. Polarization microscopy of impacted yarns reveals differences in birefringence within the fibers close to the hole made by the projectile compared with the same fiber at a greater distance from the hole. Heat is an energy sink, and depending on how, when, and where it is generated, can degrade the ballistic performance of the yarns. The quantitative importance of heat in affecting ballistic panel performance is elusive: consequently, the discussion presented here is largely qualitative.

Influence of Reinforcing Layer Orientation on Impact Response of Plain Weave RTM Composites

Two-dimensional fabric forms such as plain weaves are increasingly being considered as the reinforcement of choice for large composite structures ranging from ballistic panels and tank hulls to marine and offshore structural components. A number of these are subject to out-of-plane impact. This paper addresses the influence of stacking sequence on resistance to static and low velocity dynamic penetration. A series of seven layer 24 oz. plain weave E-glass reinforced vinyl-ester composites were manufactured using the RTM process and their response was investigated through static and low-velocity impact testing. Inelastic Energy Curves were used in conjunction with measured projected damage areas and fiber bundle fractures to describe the dynamic behavior. Static and dynamic resistance to penetration is seen to increase with a non-zero delta between adjacent fabric layers. Trends observed during static testing compare well with dynamic behavior and the type of damage observed is similar. Final puncture depends predominantly on the number of fiber bundles fractured or pushed aside to provide a path for penetration.

Penetration of Nylon Ballistic Panels by Fragment-Simulating Projectiles

The purpose of this report is to present evidence supporting the thesis that the major mode of penetration of nylon ballistic panels by fragment-simulating projectiles is a cutting, shearing mechanism: Shear forces required for yarn failure are usually less than tensile forces. Penetration is always at a slight angle, with the 90° edge of the FSP leading. Many yarn ends terminated in a smooth surface (in a tensile break the filaments break at random places along the yarn). Penetration of the cloth in certain experimental situations occur in a manner precluding tensile failure. The force required for nylon or Kevlar yarn failure is less for a rectangular leading surface than it is for a chisel-shaped leading surface.

Penetration of Nylon Ballistic Panels by Fragment-Simulating Projectiles

The main purpose of this report is to present an analysis of the ballistic behavior of the fragment-simulating projectile (FSP)-nylon cloth system. For a set of Vc determinations, plots of Vr versus Vs can be adequately represented by hyperbolas. The energy lost by an FSP after complete passage through a nylon ballistic panel of L layers is virtually constant, independent of the striking velocity. The hyperbolas lie on a portion of the surface of a hyperbolic paraboloid with Vr, Vs, and L as axes. The minimum penetration velocity of a missile that has reached the plane of the Lth layer is practically equal to the Vc (or V50) for L layers. The work of penetration per interior layer is essentially constant. For the interior layers, the average force and average deceleration per layer are approximately 1.03 times 104 N and 9.34 times 106 m/s2, respectively. This behavior holds for bonded (laminated) nylon ballistic panels, for the FSP-Kevlar system, and for the right-circular-cylinder missile/nylon system so far. Response surfaces are given for the FSP-nylon and FSP-bonded nylon systems relating ballistic performance to the diameter of the FSP, the firing obliquity, and the number of layers of cloth in the panel. The associated three-dimensional plots are also provided.