Ballistic Materials Research Articles

An integrated approach towards future ballistic neck protection materials selection

Ballistic protection for the neck has historically taken the form of collars attached to the ballistic vest (removable or fixed), but other approaches, including the development of prototypes incorporating ballistic material into the collar of an under body armour shirt, are now being investigated. Current neck collars incorporate the same ballistic protective fabrics as the soft armour of the remaining vest, reflecting how ballistic protective performance alone has historically been perceived as the most important property for neck protection. However, the neck has fundamental differences from the thorax in terms of anatomical vulnerability, flexibility and equipment integration, necessitating a separate solution from the thorax in terms of optimal materials selection. An integrated approach towards the selection of the most appropriate combination of materials to be used for each of the two potential designs of future neck protection has been developed. This approach requires evaluation of the properties of each potential material in addition to ballistic performance alone, including flexibility, mass, wear resistance and thermal burden. The aim of this article is to provide readers with an overview of this integrated approach towards ballistic materials selection and an update of its current progress in the development of future ballistic neck protection.

The Effects of Stacking Sequence Layers of Hybrid Composite Materials in Energy Absorption under the High Velocity Ballistic Impact Conditions: An Experimental Investigation

In the current study, the effects of stacking sequence layers of hybrid composite materials on ballistic energy absorption, which were fabricated from Kevlar, carbon, glass fibres, and resin have been experimentally investigated at the high velocity ballistic impact conditions. All the samples have equal mass, shape, and density, nevertheless, they have different stacking sequence layers. After running the ballistic test in the same conditions, the final velocities of the bullets showed that how much energy absorbed by the samples. The energy absorption of each sample through the ballistic impact has been calculated, accordingly, the decent ballistic impact resistance materials could be found by conducting the test. This paper can be further studied in order to characterize the material properties.

In silico assembly and nanomechanical characterization of carbon nanotube buckypaper

Carbon nanotube sheets or films, also known as ‘buckypaper’, have been proposed for usein actuating, structural and filtration systems, based in part on their unique and robustmechanical properties. Computational modeling of such a fibrous nanostructure is hinderedby both the random arrangement of the constituent elements as well as the time- andlength-scales accessible to atomistic level molecular dynamics modeling. Here we presenta novel in silico assembly procedure based on a coarse-grain model of carbonnanotubes, used to attain a representative mesoscopic buckypaper model thatcircumvents the need for probabilistic approaches. By variation in assembly parameters,including the initial nanotube density and ratio of nanotube type (single- anddouble-walled), the porosity of the resulting buckypaper can be varied threefold, fromapproximately 0.3 to 0.9. Further, through simulation of nanoindentation, theYoung’s modulus is shown to be tunable through manipulation of nanotube typeand density over a range of approximately 0.2–3.1 GPa, in good agreement withexperimental findings of the modulus of assembled carbon nanotube films. In addition tocarbon nanotubes, the coarse-grain model and assembly process can be adaptedfor other fibrous nanostructures such as electrospun polymeric composites, highperformance nonwoven ballistic materials, or fibrous protein aggregates, facilitating thedevelopment and characterization of novel nanomaterials and composites as well as theanalysis of biological materials such as protein fiber films and bulk structures.

Predicting mesh-independent ballistic limits for heterogeneous targets by a nonlocal damage computational framework

During highly dynamic and ballistic loading processes, large inelastic deformation associated with high strain rates leads, for a broad class of heterogeneous materials, to degradation and failure by localized damage and fracture. However, as soon as material failure dominates a deformation process, the material increasingly displays strain softening and the finite element predictions of ballistic response are considerably affected by the mesh size. This gives rise to non-physical description of the ballistic behavior and mesh-dependent ballistic limit velocities that may mislead the design of ballistic resistant materials. This paper is concerned with the development and numerical implementation of a coupled thermo-hypoelasto-viscoplastic and thermo-viscodamage constitutive model within the laws of thermodynamics in which an intrinsic material length scale parameter is incorporated through the nonlocal gradient-dependent damage approach. This model is intended for impact and ballistic penetration and perforation problems of heterogeneous metallic targets such as metal matrix composites with dispersed particles at decreasing microstructural length scales. An evolution equation for the material length scale as a function of the material microstructural features (e.g. mean grain size in polycrystalline materials or particle size and inter-particle spacing in metal matrix composites), course of plastic deformation, strain hardening, strain-rate hardening, and temperature is presented. It is shown through simulating plugging failure in ballistic penetration of high-strength steel targets of different thicknesses by a hard blunt projectile that the length scale parameter plays the role of a localization limiter allowing one to obtain meaningful values for the ballistic limit velocity independent of the finite element mesh density. It is also shown that a local damage model incorporating viscosity and heat conduction as localization limiters, which are known to implicitly introduce length scale parameters, is insufficient in illuminating the mesh sensitivity at impact velocities close to the ballistic limit and that the mesh sensitivity increases as the target thickness increases. Therefore, the proposed nonlocal damage model leads to an improvement in the modeling and numerical simulation of high velocity impact related problems.

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

Development and verification of a meso-scale based dynamic material model for plain-woven single-ply ballistic fabric

A meso-scale unit-cell based continuum material constitutive model has been developed for plain-woven single-ply ballistic fabric materials. This model, due to its computational efficiency, is suitable for use in computational analyses of the ballistic-protection performance of multi-layer body-armor vests. The model utilizes the continuum-level in-plane and out-of-plane deformation-state of the material, an energy minimization procedure and a simple account of yarn slip to update the structure/architecture of the fabric unit cell. Forces and moments developed within the structural components of the unit cell are then used to compute the continuum-level stress state at the material points associated with the unit cell in question. The model is implemented in a user-material subroutine suitable for use within commercial finite-element programs. To validate the model, a series of transient non-linear dynamic analyses of the impact of a square-shaped fabric patch with a spherical projectile is carried out and the computed results compared with their counterparts obtained using a more traditional finite-element approach within which yarns and yarn weaving are modeled explicitly. The results obtained show that the material model provides a reasonably good description for the fabric deformation and fracture behavior under a variety of boundary conditions applied to fabric edges and under varying fictional conditions present at the yarn/yarn and projectile/fabric interfaces. In addition, the overall ballistic energy absorption capacity of the fabric as well as its yarn-strain energy, yarn-kinetic energy, and frictional sliding contributions are predicted with reasonable accuracy by the proposed material model for fabric.

Utilization of Technology of Explosive Welding at Development of Multilayer Ballistic Resistant Materials

The technology of explosive welding (EXW) was used for development of metallic multilayer ballistic resistant materials. Explosive cladded two or multilayer materials serve as final product or as semi-finished product for further processing, e.g. rolling. The objective is to create material with sufficient ballistic resistance at relatively small thickness of the resulting multilayer structure. Under retaining the weight of armoured vehicle its ballistic resistance can be increased or, under retaining its existing ballistic resistance the weight can be reduced. Resulting material should be producible of commercially available metallic materials using common technologies, especially the technology of roll welding (ROW). For the primary tests it is possible to model the resulting structure by means of EXW and some its properties can be verified in the initial stage of research of the multilayer structure (e.g. tests of heat processing, verification of diffusion processes, behaviour under various types of load, verification of ballistic resistance and other technological tests). Subsequently, production can start of large semi-finished products by means of ROW technology. Effective preparation is possible of the samples of multilayer materials by means of EXW technology in various material combinations - armour steel, tool steel and interlayer based on nickel, nickel alloys etc.

Advances in X-ray Computed Tomography Diagnostics of Ballistic Impact Damage

With the relatively recent introduction of quantitative and volumetric X-ray computed tomography (XCT) applied to ballistic impact damage diagnostics, significant inroads have been made in expanding our knowledge base of the morphological variants of physical impact damage. Yet, the current state of the art in computational and simulation modeling of terminal ballistic performance remains predominantly focused on the penetration phenomenon, without detailed consideration of the physical characteristics of actual impact damage. Similarly, armor ceramic material improvements appear more focused on penetration resistance than on improved intrinsic damage tolerance and damage resistance. Basically, these approaches minimize our understanding of the potential influence that impact damage may play in the mitigation or prevention of ballistic penetration. Examples of current capabilities of XCT characterization, quantification, and visualization of complex impact damage variants are demonstrated and discussed for impacted ceramic and metallic terminal ballistic target materials. Potential benefits of incorporating such impact damage diagnostics in future ballistic computational modeling are also briefly discussed.

North Korea's Missile Program and US Nonproliferation Strategy

Abstract Even though it is said that North Korea's missile development is a self-defense measure against US invasion tactics, its sovereign right, and that it provides powerful diplomatic and political leverage, no doubt the North's short and medium-range missiles are a growing threat. It should be clear that another long-range missile launch would have serious consequences for regional security and return the peninsula to a state of high tension. Furthermore, Pyongyang's exports including ballistic missile-related equipment, components, materials, technical expertise, and complete systems to a variety of Third World countries in the Middle East, South Asia and North Africa bring about missile proliferation, and the possibility of falling into the terrorist hands. North Korea will not easily give up its missile program because it is absolutely necessary for obtaining hard currency, which props up the socialist regime, and increases its defense capabilities. It is suggested that both sides continue the talks with patience. Brinkmanship strategy will help neither side. A comprehensive package deal might be a solution, but if that is not possible then perhaps the North could give up development of long-range missiles and halt missile export, withdrawing missile deployment rearward. In return the US would remove the DPRK from its terrorism list and ease economic sanctions. North Korean satellites could be launched by a third country.

Simulation of powder die compaction with consideration of cracking

The military ballistic protection market has reached approximately US$ 10 billion/year, and the civil market is also very significant and is steadily increasing, which drives research for new ballistic protection alternatives. Materials currently used and under development as transparent ballistic protection devices include glasses, glass–ceramics, single and polycrystalline ceramics, and polymer-composites. Glass–ceramics are a less expensive, versatile alternative to currently used transparent ceramics. Glass–ceramics are generally harder, stiffer, tougher, and stronger than glasses, and can be made transparent or opaque, according to the needs of the protective system. They can be easily shaped in simple or complex forms, are much less expensive than carbides and nitrades, and are less dense than transparent alumina or spinel. This positive combination of properties makes glass–ceramics suitable for a wide range of applications. However, for an effective development of new transparent glass–ceramics (TGC), it is vital to understand which key properties must be optimized. In this review, we compile information on the role of each material in multi-layer ballistic systems, give a brief description of ballistic impact, and the properties related to it, and discuss the development of TGC to be used as ballistic protection. Our aim is to describe the most important ballistic protection materials and to indicate the pathways that research on TGC for ballistic protection have taken. We finish by concluding that there are still several opportunities that warrant further research on this particular application of glass–ceramics.

A numerical investigation of penetration in multilayered material/structure systems

The response of multilayered ceramic/steel targets to high velocity impact and penetration has been investigated through finite element simulations. A multiple-plane microcracking model has been used to describe the inelastic constitutive behavior of ceramics in the presence of damage. The model has been integrated into the finite element code EPIC95, which possesses contact and erosion capabilities particularly suitable for ballistic simulations. The integrated code has been used to analyze the depth of penetration (DOP) and interface defeat (ID) ceramic target configurations. Parametric analyses have been carried out to establish the effect of ceramic materials, target configuration design for ceramic confinement, diameter/length ( d/L) ratio of the penetrator, material erosion threshold levels and the use of a shock attenuator on the response of multilayered targets subjected to high velocity impact. The response characteristics are established in terms of the parameters which can be measured experimentally. The analyses show that the integrated code is able to predict the response of ceramic targets in confirmation with experimental findings reported in the literature. The penetration process is found to be less dependent on the ceramic materials as usually assumed by most investigators. By contrast, the penetration process is highly dependent on the multilayered configuration and the target structural design (geometry, and boundary conditions). From a simulation standpoint, it has been found that the erosion parameter plays an important role in predicting the deformation history and interaction of the penetrator with the target. These findings show that meaningful lightweight armor design can only be accomplished through a combined experimental/numerical study in which relevant ballistic materials and structures are simultaneously investigated.

Measurements of internal friction coefficient of SiC and Al2O3 powders

The frictional strength of the powder of two ballistic materials (SiC and Al2O3) under low confining pressures has been studied statically and dynamically. In the static tests, the influence of the ceramic fragment size upon the internal friction coefficient value was investigated. In the dynamic tests, the effect of the ceramic fragment size, the relative sliding velocity and the confinement load were studied. It was found in the experimental conditions, that the influence of the fragment size and of the relative sliding velocity upon the internal friction coefficient value of comminuted SiC and Al2O3 is important.

Ballistic Materials and Penetration Mechanics

The American Journal of Forensic Medicine and Pathology: June 1982 - Volume 3 - Issue 2 - p 190