Armor Composites Research Articles

Ballistic performance of composite armor impacted by 7.62 mm armor projectile

The purpose of this study is to investigate the effectiveness of composite armor against 7.62 mm ballistic threats. A sandwich panel construction consisting of a 96% alumina ceramic strike face, an annealed aluminum alloy 7075 cubic lattice sandwich panel, and a thin aluminum backing plate were used to create hard armor. The ballistic test based on NIJ standard level III was performed using 7.62 mm × 51 mm NATO projectiles at an impact velocity of 847 ± 9.1 m∙s-1. The influences of the alumina strike face panel with thicknesses of 7, 10, and 14 mm on the ballistic performance were investigated. The results of the ballistic test suggest that hard armor designs can resist a ballistic impact of 7.62 mm × 51 mm NATO projectiles without penetrating them. With the increase in thickness of alumina ceramic tile, the deformation of the aluminum backing plate decreased. Furthermore, the annealed aluminum alloy 7075 cubic lattice sandwich panel could be able to absorb the residual kinetic energy of the projectile after it was eroded by the ceramic strike panel. The damaged targets after ballistic impact were presented. Collectively, these results indicate that the armor composites in this study may be used in military vehicle applications.

Flexural strength and ballistic performance of vinyl ester resin/aramid fiber composites toughened by graphene nanosheets

The fiber reinforced polymer (FRP) armor composites are kinds of composite materials specially designed and manufactured to prevent the penetration of high-speed bullets and fragments. The FRP composites are commonly composed of reinforcing fibers, resin matrix and their interfacial structures. The vinyl ester resin (VER) is a kind of thermosetting resin commonly applied in the field of high performance bulletproof composites. However, the VER has the problem of insufficient toughness after curing, which seriously limits its application. In this research, the graphene nanosheets were homogeneously dispersed into VER matrix by ultrasonic-assisted dispersing process. The effects of graphene content on the mechanical and dynamic mechanical thermal properties of VER castings were investigated. The graphene-toughened VER/aramid fiber (AF) composites were prepared by hand layup-vacuum bag molding process. The influences of graphene content on the flexural strength and ballistic resistance of VER/AF composites were investigated. The results showed that the tensile strength, elongation at break, flexural strength and non-notch impact strength of VER casting filled with 0.1 wt.% graphene increased by 5.6%, 27.6%, 11.7% and 90.5%, respectively, compared with those of unfilled VER casting. The glass transition temperature Tg of VER casting gradually increased with the increase of graphene content. The hand layup-vacuum bag molding process effectively reduced the filtering effect of the fiber fabrics on graphene sheets. When the amount of graphene was 0.1 wt.%, the flexural strength of VER/AF composite was increased by 34.2%. Due to the improvement of fracture toughness of the resin matrix, the ballistic limit velocity V 50 and specific energy absorption of the VER/AF composites were both improved.

Functional Nanocomposites in the Development of Flexible Armor

The idea of flexible body armor has been around for many years. Initial development included shear thickening fluid (STF) as a backbone polymer to impregnate ballistic fibers such as Kevlar. At the core of the ballistic and spike resistance was the instantaneous rise in viscosity of STF during impact. Increase in viscosity was due to the hydroclustering of silica nanoparticles dispersed in polyethylene glycol (PEG) through a centrifuge and evaporation process. When STF composite was dry, hydroclustering was not possible due to absence of any fluidity in PEG. However, particles embedded within the polymer, covered the Kevlar fiber and offered some resistance to spike and ballistic penetration. The resistance was meagre and hence, the goal was to improve it further. This was achieved by creating chemical bonds between particles, and by strongly attaching particles to the fiber. PEG was replaced with silane (3-amino propyl trimethoxysilane), and a fixative cross-linker, Glutaraldehyde (Gluta), was added. Silane installed an amine functional group on the silica nanoparticle surface, and Gluta created strong bridges between distant pairs of amine groups. Amide functional groups present in Kevlar also interacted with Gluta and silane to form a secondary amine, allowing silica particles to attach to fiber. A network of amine bonding was also established across the particle-polymer-fiber system. In synthesizing the armor, silica nanoparticles were dispersed in a mixture of silane, ethanol, water, and Gluta, maintaining an appropriate ratio by weight, and using a sonication technique. Ethanol was used as a dispersion fluid and was evaporated later. Several layers of Kevlar fabric were then soaked with the admixture for about 24 h and dried in an oven. Armor composites were tested in a drop tower according to NIJ115 Standard using spikes. Kinetic energy at impact was calculated and normalized with the aerial density of the armor. NIJ tests revealed that normalized energy for 0-layer penetration increased from 10 J-cm2/g (STF composite) to 220 J-cm2/g for the new armor composite, indicating a 22-fold enhancement. SEM and FTIR studies confirmed that this high resistance to spike penetration was due to the formation of stronger C-N, C-H, and C=C-H stretches facilitated by the presence of silane and Gluta.

Properties of Kevlar fabric composites reinforced by STF composed of monodisperse polystyrene microspheres

Shear thickening fluid (STF) composed of monodisperse polystyrene microspheres (m-PS-m) was prepared, and soft armor composites was constructed with Kevlar fabric reinforced by this STF in this work. Both the knife and the spike stab resistance performance of this soft composite are investigated and discovered to improve significantly over the neat Kevlar fabric (NKF), and the puncture resistance of the spike is dramatically superior to the cut resistance of the knife. 8 layers of STF-impregnated Kevlar fabric (STKF) will not be punctured under the highest impact energy while 10 sheets of NKF is impaled easily even under the lowest striking energy in experiments. The tensile strength of this soft composite is increased by more than 55% compared to NKF. The highest pull-out force for single yarn in STKF is nearly 6 times that of NKF. The highest pull-out force of single yarn and tensile strength for STKF are greatly improved to make it meet more requirements of different situations. More importantly, the excellent stab resistant and burst strength performance of STKF indicate that it has broad application prospects in the field of soft body armor.

Research Progress of Numerical Simulation Method Based on the Protection Performance of STF-Kevlar Fabric Liquid Armor Composites

In this paper, the numerical simulation method for the protection performance of liquid armor based on STF can be roughly summarized into two ways, containing the shell element simulation method based on the inter-yarns friction coefficient and the coupled Euler-Lagrangian simulation method. The shell element simulation method of inter-yarns friction coefficient has a single consideration for STF performance, but it has high calculation efficiency and low calculation cost. The coupled Euler-Lagrangian simulation method fully considers the shear thickening characteristics of STF, and comprehensively considers the characteristics of STF. The simulated performance gets closer to the actual situation, and it can also reveal the effect of STF in improving the protection performance.

Influence of Degradation on the Ballistic Behavior of Aramid Fabric Reinforced Polymeric Armor Composites

Polymeric fibers are used for reinforcement of composites in all kinds of applications, from sport and recreation products to military equipment. Since these fibers have high energy absorption on ballistic impact, the defense industry uses them to manufacture lightweight armor. In many cases, armors are exposed to degradation agents such as heat, humidity, and radiation. The macromolecular changes of polymer fibers exposed to degradation agents can affect the mechanical and ballistic properties of the composite. The present work studies the ballistic performance of aromatic polyamide (aramid) fabric-reinforced composite using two different matrices, degraded by gamma radiation. The results suggest that gamma radiation can change the penetration failure mechanism of the composite in a variety of ways depending on the matrix, compromising its performance.

A review of recent research on materials used in polymer–matrix composites for body armor application

The development of personal protection systems with improved ballistic performance and reduced weight has received a great interest in the last decade with the unfortunate ever-increasing threats and conflicts. In this review, the ordinarily polymeric fibers used in body armors manufacturing were first reported, then some nanomaterials, such as carbon nanotubes and graphene with advanced structural and mechanical properties, as well as their potential reinforcement of armor composites were investigated through some recent studies available in the literature. Additionally, natural fibers integrated into multilayered armor systems, and ballistic tests which endorse their future importance were also cited. This short review which sheds light on novel materials used in personal armor systems, a specific and an important topic that was not previously reviewed, aims to provide to the new researchers, engineers and manufactures in this field some guidelines about what are the promising materials that can be used in order to construct the ultimate body armors of the future.

Effect of surface texture and structure on the development of stable fluvial armors

Stable fluvial armors are found in river systems under conditions of partial sediment transport and limited sediment supply, a common occurrence in nature. Stable armoring is also readily recreated in experimental flumes. Initially, this bed stabilizing phenomenon was examined for different flow discharges and solely related to surface coarsening and bedload transport reduction. The models developed suggest a specific armor composition (i.e., texture) dependent on the parent bed material and formative discharge. Following developments in topographic remote sensing, recent research suggests that armor structure is an important control on bed stability and roughness. In this paper, replicated flume runs during which digital elevation models (DEMs) were collected from both exposed and flooded gravel beds are used to interpret armoring manifestations and to assess their replicability. A range of methodologies was used for the analysis, providing information on (i) surface grain size and orientation, (ii) bed-elevation distributions, (iii) the spatial coherence of the elevations at the grain-scale, (iv) surface slope and aspect, (v) grain imbrication and (vi) the spatial variability in DEM properties. The bed-surface topography was found to be more responsive than bed-material size to changes in flow strength. Our experimental results also provide convincing evidence that gravel-beds' response to water-work during parallel degradation is unique (i.e., replicable) given the formative parameters. Based on this finding, relationships between the armors' properties and formative parameters are proposed, and are supported by adding extensive data from previous research.

Ballistic performance of front-facing fluoropolymer-coated armor composites

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.

The influence of aqueous armor composition for TNT–RDX explosive charge on the yield and quality of detonation nanodiamond and diamond-containing soot in detonation synthesis

The paper addresses the detonation synthesis factors that govern the yield of nanodiamonds and diamond-containing soot, and their quality. The effect of such an important factor as the composition of armor (shell) of the explosive charge is described. The authors discuss three different methods of initiating an explosive charge, which involve the use of gas, water, or ice, respectively, and their advantages and disadvantages. The influence of the composition of mixtures of aqueous solutions of various substances (organic and inorganic) on the outcome of the detonation synthesis is shown in detail.

Cartographie De L’état Du Couvert Végétal Du Nord De La Côte D’ivoire À Partir D’images Satellites: Exemple De La Zone De Korhogo

The purpose of this study is to determine the state of the vegetation cover in the region of Korhogo through remote sensing. Nowadays, the problem of desertification in the Sahel is serious. This could be explained by the phenomenon of climate change. We want to map the state of the vegetation cover in the study area. This study therefore focuses on the state of the vegetation cover in the region of Korhogo in northern Côte d’Ivoire. We will use one Landsat satellite image from December 16th 2000 and proceed with image processing. Processing techniques by the normalized difference vegetation index, the index armor and colorful composition 472. After these treatments in our pictures, we observe the behavior of vegetation. We can then get an overview of the vegetation in this area.

A Study on Propagation Characteristic of One-dimensional Stress Wave in Functionally Graded Armor Composites

The development of Functionally Graded Materials (FGM) for energy-absorbing applications requires understanding of stress wave propagation in these structures in order to optimize their resistance to failure. One-dimensional stress wave in FGM composites under elastic and plastic wave loading have been investigated. The stress distributions through the thickness and stress status have been analyzed and some comparisons have been done with the materials of sharp interfaces (two-layered material). The results demonstrate that the gradient structure design greatly decreases the severity of the stress concentrations at the interfaces and there are no clear differences in stress distribution in FGM composites under elastic and plastic wave loading.

Effect of Heat Treatment on Microstructures and Hardness of SiC/Steel Armor Composite

The SiC reinforced ferrous based armor composites were treated with three heat treatments of annealing, isothermal quenching and annealing. The relationships between the treatment processing and the microstructures and hardness of the composite material were investigated. The results revealed that the heat treatment had scarcely any influence on the reinforced component but there appeared iron silicide existing at the interface of the two component, and the hardness of the component changed in three same treatment situation, the highest hardness of the matrix reached 532HB after subjecting to the isothermal quenching at 300°C.

Enhanced stab resistance of armor composites with functionalized silica nanoparticles

Traditionally shear thickening fluid (STF) reinforced with Kevlar has been used to develop flexible armor. At the core of the STF-Kevlar composites is a mixture of polyethylene glycol (PEG) and silica particles. This mixture is often known as STF and is consisted of approximately 45 wt % PEG and 55 wt % silica. During rheological tests, STF shows instantaneous spike in viscosity above a critical shear rate. Fabrication of STF-Kevlar composites requires preparation of STF, dilution with ethanol, and then impregnation with Kevlar. In the current approach, nanoscale silica particles were dispersed directly into a mixture of PEG and ethanol through a sonic cavitation process. Two types of silica nanoparticles were used in the investigation: 30 nm crystalline silica and 7 nm amorphous silica. The admixture was then reinforced with Kevlar fabric to produce flexible armor composites. In the next step, silica particles are functionalized with a silane coupling agent to enhance bonding between silica and PEG. The performance of the resulting armor composites improved significantly. As evidenced by National Institute of Justice spike tests, the energy required for zero-layer penetration (i.e., no penetration) jumped twofold: from 12 to 25 J cm2/g. The source of this improvement has been traced to the formation of siloxane (Si-O-Si) bonds between silica and PEG and superior coating of Kevlar filaments with particles. Fourier transform infrared, x-ray photoemission spectroscopy, and scanning electron microscopy studies were performed to examine chemical bonds, elemental composition, and particle dispersion responsible for such improvement. In summary, our experiments have demonstrated that functionalization of silica particles followed by direct dispersion into PEG resulted in superior Kevlar composites having much higher spike resistance.

Scalable computing for the transient elasto-plastic impact analysis of composite armor using the homogenization method

This paper describes impact analyses of armor composites using concurrent coupling of scales through asymptotic expansion homogenization (AEH) in elasto-plastic and transient settings. The AEH method is applied with an explicit time integration algorithm for the transients and an updated Lagrangian scheme for the large displacements. The primary aim of this paper is to present numerical validations against the experiments of S. Zhuang, G. Ravichandran and D.E. Grady [An experimental investigation of shock wave propagation in periodically layered composites. J Mech Phys Solids 2003;51:245–65] and S. Zhang [Shock wave propagation in periodically layered composites, PhD thesis, California Institute of Technology, Pasadena, CA, 2002] to demonstrate the validity of the computational method for layered armor composites. A parallel computer program was developed to handle the parallel computations across multiple scales and then integrated with a widely available explicit dynamics finite element program. A brief scalability study demonstrates the computational viability of the method.

A graded stream response relation for bed load–dominated streams

The relation between equilibrium stream channel morphology and three independent governing variables, discharge, sediment supply, and valley slope, is investigated using a stream table. The experiments are based on a generic physical model of a laterally active gravel bed stream and directed by a recently published rational regime model. While a variety of channel adjustments are possible, the primary adjustment observed was in the channel slope. Other adjustments, such as surface armor composition and cross‐sectional shape, were minor in comparison. The equilibrium slope is well predicted by a linear function of sediment concentration which is bounded by two thresholds: one associated with the minimum stream power necessary to deform the bed and the other associated with the maximum sediment feed that can be transported by the available flow. The results suggest that the system tends to move toward the minimum slope capable of transporting the sediment supply, in the process increasing the flow resistance for the system. Whether or not a minimum slope or a maximum system‐scale flow resistance is reached cannot be determined given the available data, but there appears to be a unique slope (or, at least, a limited range of slopes) for which a stable alluvial channel morphology can be established for a given sediment concentration. The implications of this behavior are evaluated for the theoretical basis of the extremal hypothesis used to close the formulation of a rational regime model.

Chameleon: a software infrastructure for adaptive fault tolerance

This paper presents Chameleon, an adaptive infrastructure, which allows different levels of availability requirements to be simultaneously supported in a networked environment. Chameleon provides dependability through the use of special ARMORs-Adaptive. Reconfigurable, and Mobile Objects for Reliability-that control all operations in the Chameleon environment. Three broad classes of ARMORs are defined: 1) Managers oversee other ARMORs and recover from failures in their subordinates. 2) Daemons provide communication gateways to the ARMORs at the host node. They also make available a host's resources to the Chameleon environment. 3) Common ARMORs implement specific techniques for providing application-required dependability. Employing ARMORs, Chameleon makes available different fault-tolerant configurations and maintains run-time adaptation to changes in the availability requirements of an application. Flexible ARMOR architecture allows their composition to be reconfigured at run-time, i.e., the ARMORs may dynamically adapt to changing application requirements. In this paper, we describe ARMOR architecture, including ARMOR class hierarchy, basic building blocks, ARMOR composition, and use of ARMOR factories. We present how ARMORs can be reconfigured and reengineered and demonstrate how the architecture serves our objective of providing an adaptive software infrastructure. To our knowledge, Chameleon is one of the few real implementations which enables multiple fault tolerance strategies to exist in the same environment and supports fault-tolerant execution of substantially off-the-shelf applications via a software infrastructure only. Chameleon provides fault tolerance from the application's point of view as well as from the software infrastructure's point of view. To demonstrate the Chameleon capabilities, we have implemented a prototype infrastructure which provides set of ARMORs to initialize the environment and to support the dual and TMR application execution modes. Through this testbed environment, we measure the execution overhead and recovery times from failures in the user application, the Chameleon ARMORs, the hardware, and the operating system.

Army focused research team on functionally graded armor composites

With the emphasis on smaller but more mobile combat forces to meet a broad range of mission requirements, future weapon platforms and upgrades will require materials to do better, do more, weigh less, size less and cost less. Metal matrix composites (MMCs) are such material candidates for niche Army applications such as armor, armaments, and vehicle structures. Under the shadow of shrinking resources, a focused research team (FRT) composed of the US Army Research Laboratory (ARL), academia, and small business was assembled to address MMC issues for Army applications. The immediate focus of this team is on the development of MMCs with a tailored ceramic-to-metal through-thickness gradient known as functionally graded armor composites (FGACs). The goal is to provide the science and technology to deliver a high space and mass efficient armor material for ballistic protection against light to medium threats. Technical issues being addressed by this team encompass the role of microstructure in affecting the dynamic flow and ballistic performance of FGACs, high-resolution non-destructive evaluation (NDE) techniques, joining FGACs to dissimilar materials, and the availability of versatile low-cost near-net-shape processing of FGACs. In this paper, highlights from these activities are presented. They include high-strain-rate testing and modeling, apertureless near-field optical scanning microscopy (ANSOM) of FGACs, micro- and nano-scale self-propagating high-temperature synthesis (SHS) reactions, ballistic evaluation, and pressure assisted casting. These efforts represent key technologies necessary for prompt delivery of FGAC technology to the warfighter.

Armored Mud Balls in an Intertidal Environment, Minas Basin, Southeast Canada

Armored mud balls presently forming on a wave-cut bench in the intertidal zone on the north shore of the Minas Basin, Nova Scotia, differ from more spherical mud balls formed in alluvial flood plains and deep marine environments. Tidal action shapes angular blocks and plates of plastic mud into rounded to well-rounded armored triaxial ellipsoids by a back-and-forth rolling motion on the inclined gravel-covered platform. Balls become rapidly reduced to fairly uniform size; their long axes on the lower part of the platform tend to parallel the shoreline. A number of armored ellipsoids are found partially buried. These structures are occasionally preserved in ancient intertidal deposits. An evaluation of their size, shape, armor composition, and particular orientation in relation to shorelines can thus be of use in paleogeographic reconstructions.