Ballistic Penetration Resistance Research Articles

Mesoscale modeling of ballistic impact experiments on a single layer of plain weave composite

To gain fundamental understanding of energy absorbing mechanisms during high velocity impact of plain weave S-2 glass/epoxy composites, single layer composites are ballistically tested and modeled. To avoid boundary condition effects, targets were 0.6 m by 0.6 m with free boundaries. Targets were perforated by 17 grain, 0.22 caliber fragment simulating projectiles . Experiments focused on determining ballistic limit velocity and the associated damage modes. The experiments were simulated with a continuum finite element model with effective plain weave properties that predicted the ballistic limit velocity with 6% error. A mesoscale model that incorporates the woven fabric architecture and lower length scale energy absorbing mechanisms was also developed. The mesoscale model includes accurate geometry and fiber volume fraction , rate-dependent matrix behavior, and important damage mechanisms including tow-tow delamination , tow pullout and frictional sliding . The mesoscale model predicted ballistic limit velocity with 1% error and more accurately predicts the deformation modes during ballistic impact and penetration than the continuum modeling approach. The mesoscale model indicated two phases of penetration, the first dominated by momentum transfer and the second dominated by tow tension and pullout. In a materials-by-design framework, the mesoscale model was used to quantify energy dissipation and identify important damage mechanisms that could be optimized to provide improved ballistic penetration resistance .

Influence of Post Weld Cryogenic Treatment on the Ballistic Penetration Resistance of Friction Stir-Welded AZ31B Magnesium Alloy

Influence of post weld cryogenic treatment conditions (deep and shallow) on the ballistic resistance of friction stir welded (FSW) AZ31B magnesium alloy has been investigated. AZ31B welded joints which were prepared by using friction stir welding process were subjected to two types of cryogenic treatment conditions. The microstructural investigation of cryogenic treated joints showed the formation of Mg17Al12 precipitates and conversion of coarse eutectic phase into thin discontinues phase along with halos. In addition, superior microhardness values were noticed for the cryogenically treated joints compared with non-treated joints and base metal. High velocity ballistic experiments were conducted on cryogenically treated and non-treated weld targets using 7.62 mm deformable projectiles at an initial velocity of 450 ± 10 m/s. At the stir zone, the depth of penetration (DOP) of the projectile into the deep cryogenic treated (DCT) target was observed to be 11% and 34 % lesser than the shallow cryogenic treated (SCT) and FSW targets. Thus increase in the ballistic resistance was observed for the post-weld cryogenic treated FSW joints compared to non-treated FSW joints. SEM investigation of the projectile impacted DCT targets showed the formation of cracks, dimples and micro voids at the crater region. It is also noticed that, the Stir Zone (SZ) and Heat Affected Zones (HAZ) of the DCT target has effectively absorbed the ballistic impact energy of the projectile by a ductile fracture and hence DCT can be used to improve the ballistic penetration resistance of the FSW joints at the SZ and HAZ regions.

Design and Ballistic Penetration of “SiC/Ti6Al4V/UHMWPE” Composite Armor

The penetration resistance of “SiC/Ti6Al4V/UHMWPE” composite armor, which involves four different constructions at the same area density, has been designed and presented against 12.7 mm armor piercing (AP) projectiles experimentally. Three armor materials, including silicon carbide (SiC), Ti6Al4V, and ultra-high molecular weight polyethylene (UHMWPE) fiber composite, were prepared together with the investigation on their mechanical properties. Subsequently the composite armors were manufactured by adhesive technology. The ballistic test results show that the target of SiC/UHMWPE and Ti6Al4V/UHMWPE exhibits better penetration resistance against 12.7 mm AP. The study on the protective mechanism indicates that the thicker ceramic front layer can prolong the interaction time with the projectile, causing more energy dissipation by blunting, eroding, and breaking the projectile efficiently and then the thicker UHMWPE backing layer can fully utilize the tensile deformation of fibers to absorb the remaining energy of the projectile. The enlarged loading area of UHMWPE backing plate caused by the deviation of projectile and the petalling fracture of Ti6Al4V can help to fully develop the tensile deformation of fibers, resulting in more energy absorption. For the target of SiC/Ti6Al4V/UHMWPE, Ti6Al4V interlayer contributes to enhancing the ballistic penetration resistance of composite armors by supporting the front ceramic layer and enlarging the loading area of UHMWPE backplate. However, the insertion of Ti6Al4V partly reduces the thickness of SiC layer and UHMWPE composite layer at the equal areal density of the system, leading to the poorer ballistic penetration resistance of the target of SiC/Ti6Al4V/UHMWPE than that of SiC/UHMWPE and Ti6Al4V/UHMWPE.

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.

Ballistic-penetration resistance and flexural-stiffness optimization of a nacre-mimetic, B4C-reinforced, polyurea-matrix composite armor

PurposeThe purpose of this paper is to model a nacre-like composite material, consisting of tablets and polyurea tablet/tablet interfaces, B4C. This composite material is being considered in the construction of the so-called backing-plate, a layer within a multi-functional/multi-layer armor system.Design/methodology/approachConsidering the basic functions of the backing-plate (i.e. to provide structural support for the ceramic-strike-face and to stop a high-velocity projectile and the accompanying fragments) in such an armor system, the composite-material architecture is optimized with respect to simultaneously achieving high flexural stiffness and high ballistic-penetration resistance. Flexural stiffness and penetration resistance, for a given architecture of the nacre-like composite material, are assessed using a series of transient non-linear dynamics finite-element analyses. The suitability of the optimized composite material for use in backing-plate applications is then evaluated by comparing its performance against that of the rolled homogeneous armor (RHA), a common choice for the backing-plate material.FindingsThe results obtained established: a trade-off between the requirements for a high flexural stiffness and a high ballistic-penetration resistance in the nacre-like composite material; and overall superiority of the subject composite material over the RHA when used in the construction of the backing-plate within multi-functional/multi-layer armor systems.Originality/valueThis study extends the authors previous research on nacre-mimetic armor to optimize the architecture of the armor with respect to its flexural stiffness and ballistic-penetration resistance, so that these properties could be increased over the levels attained in the current choice (RHA) for the backing layer of multi-functional/multi-layer armor.

Single-yarn pull-out test in neat, solvent-treated and shear-thickening fluid-impregnated Kevlar® KM2 fabric

PurposeIn order to help explain experimental findings related to the stabbing- and ballistic-penetration resistance of flexible body-armor, single-yarn pull-out tests, involving specially prepared fabric-type test coupons, are often carried out. The purpose of this paper is to develop a finite-element-based computational framework for the simulation of the single-yarn pull-out test, and applied to the case of Kevlar® KM2 fabric.Design/methodology/approachThree conditions of the fabric are considered: neat, i.e, as-woven; polyethylene glycol (PEG)-infiltrated; and shear-thickening fluid (STF)-infiltrated. Due to differences in the three conditions of the fabric, the computational framework had to utilize three different finite-element formulations: standard Lagrangian formulation for the neat fabric; combined Eulerian-Lagrangian formulation for the PEG-infiltrated fabric (an Eulerian subdomain had to be used to treat the PEG solvent/dispersant); and combined continuum Lagrangian/discrete-particle formulation for the STF-infiltrated fabric (to account for the interactions of the particles suspended in PEG, which give rise to the STF character of the suspension, with the yarns, the particles had to be treated explicitly).FindingsThe results obtained for the single-yarn pull-out virtual tests are compared with the authors’ experimental counterparts, and a reasonably good agreement is obtained, for all three conditions of the fabric.Originality/valueTo the authors’ knowledge, the present work represents the first attempt to simulate single-yarn pull-out tests of Kevlar® KM2 fabric.

Retraction Note to: Multi-Length Scale Analysis of the Effect of Fused-Silica Pre-shocking on its Tendency for Devitrification

Recent studies have suggested that impact-induced devitrification of fused silica, or more specifically formation of high-density stishovite, can significantly improve ballistic-penetration resistance of fused silica, the material which is used in transparent armor. The studies have also shown that in order for stishovite to form during a ballistic impact event, very high projectile kinetic energy normalized by the projectile/fused-silica target-plate contact area must accompany such an event. Otherwise fused-silica devitrification, if taking place, does not substantially improve the material ballistic-penetration resistance. In the present work, all-atom molecular-level computations are carried out in order to establish if pre-shocking of fused-silica target-plates (to form stishovite) and subsequent unloading (to revert stishovite to the material amorphous structure) can increase fused silica’s propensity for stishovite formation during a ballistic impact. Towards that end, molecular-level computational procedures are developed to simulate both the pre-shocking treatment of the fused-silica target-plate and its subsequent impact by a solid right-circular cylindrical projectile. The results obtained clearly revealed that when strong-enough shockwaves are used in the fused-silica target-plate pre-shocking procedure, the propensity of fused silica for stishovite formation during the subsequent ballistic impact is increased, as is the associated ballistic-penetration resistance. To rationalize these findings, a detailed post-processing microstructural analysis of the pre-shocked material is employed. The results obtained suggest that fused silica pre-shocked with shockwaves of sufficient strength retain some memory/embryos of stishovite, and these embryos facilitate stishovite formation during the subsequent ballistic impact.

Computational investigation of ballistic-impact behavior and penetration resistance of a nacre-like ceramic/polymer laminated composite

PurposeNacre is a biological material constituting the innermost layer of the shells of gastropods and bivalves. It consists of polygonal tablets of aragonite, tessellated to form individual layers and having the adjacent layers as well as the tablets within a layer bonded by a biopolymer. Due to its highly complex hierarchical microstructure, nacre possesses an outstanding combination of mechanical properties, the properties which are far superior to the ones that are predicted using techniques such as the rule of mixtures. Given these properties, a composite armor the structure of which mimics that of nacre may have improved performance over a monolithic armor having a similar composition and an identical areal density. The paper aims to discuss these issues.Design/methodology/approachIn the present work, an attempt is made to model a nacre-like composite armor consisting of B4C tablets and polyurea tablet/tablet interfaces. The armor is next tested with respect to impact by a solid right circular cylindrical (SRCC) rigid projectile, using a transient non-linear dynamics finite-element analysis. The ballistic-impact response and the penetration resistance of the armor are then compared with that of the B4C monolithic armor having an identical areal density. Furthermore, the effect of various nacre microstructural features (e.g. surface profiling, micron-scale asperities, mineral bridges between the overlapping tablets lying in adjacent layers, and B4C nano-crystallinity) on the ballistic-penetration resistance of the composite armor is investigated in order to identify an optimal nacre-like composite armor architecture having the largest penetration resistance.FindingsThe results obtained clearly show that a nacre-like armor possesses a superior penetration resistance relative to its monolithic counterpart, and that the nacre microstructural features considered play a critical role in the armor-penetration resistance.Originality/valueThe present work indicates that for a given choice of armor material, penetration resistance may be improved by choosing a structure resembling that of nacre.

Influence of Heat Treatment on the Ballistic Behavior of AA-7017 Alloy Plate against 7.62 Deformable Projectiles

Effect of heat treatment on mechanical properties and ballistic resistance of AA-7017 aluminium alloy plates has been investigated. The stress-strain behaviour of AA-7017 plates subjected to different heat treatment schedules namely under-aging, peak aging and over-aging, is evaluated from quasi-static tension tests. The heat-treated plates display large differences in static mechanical properties in terms of strength and ductility. The peak-aged plate shows the highest strength and hardness followed by the under-aged and over-aged materials. The ballistic resistance of these plates are evaluated by impacting deformable projectiles at a velocity of 830±10 m/s at a normal angle of attack. The peak-aged plate exhibits the best ballistic penetration resistance. The changes in the mechanical properties with different heat treatments have been correlated with ballistic performance of the AA-7017 alloy. Both the post ballistic micro-structural observations and micro-hardness measurements adjacent to the impacted crater walls have been carried out to understand the change in material deformation behaviour with heat treatment.

Shape- Optimized Bubbled- Armour Forms for High Resistance to Ballistic Penetration

In this study, bubbled- armour forms are assessed for ballistic penetration resistance. A key component is optimization of the bubble shape to maximize its fundamental modal frequency. A ‘large- plastic- regime’ automotive steel alloy is adopted for the bubble and the penetration process simulated by LS- DYNA for a ‘rigid’ projectile. Three forms: - a flat-, spherical and the shape- optimized one, of identical planform dimensions and mass, are studied for their penetration resistance characteristics under a common impact speed. The optimum form is found to be the most superior, causing a momentum loss of as much as 140%, implying a total reversal of the projectile, post- impact. This is more than the 111% for the spherical form and far above the 30% for the flat form. Modal response also correlates well with impact- induced bubble- response acceleration in wavelet decomposition. We conclude that with the fundamental modal frequency maximized, shape- optimized bubbled- armour forms can have much higher penetration resistance than a traditional plate armour's.

RETRACTED ARTICLE: Multi-Length Scale Analysis of the Effect of Fused-Silica Pre-shocking on its Tendency for Devitrification

Recent studies have suggested that impact-induced devitrification of fused silica, or more specifically formation of high-density stishovite, can significantly improve ballistic-penetration resistance of fused silica, the material which is used in transparent armor. The studies have also shown that in order for stishovite to form during a ballistic impact event, very high projectile kinetic energy normalized by the projectile/fused-silica target-plate contact area must accompany such an event. Otherwise fused-silica devitrification, if taking place, does not substantially improve the material ballistic-penetration resistance. In the present work, all-atom molecular-level computations are carried out in order to establish if pre-shocking of fused-silica target-plates (to form stishovite) and subsequent unloading (to revert stishovite to the material amorphous structure) can increase fused silica’s propensity for stishovite formation during a ballistic impact. Towards that end, molecular-level computational procedures are developed to simulate both the pre-shocking treatment of the fused-silica target-plate and its subsequent impact by a solid right-circular cylindrical projectile. The results obtained clearly revealed that when strong-enough shockwaves are used in the fused-silica target-plate pre-shocking procedure, the propensity of fused silica for stishovite formation during the subsequent ballistic impact is increased, as is the associated ballistic-penetration resistance. To rationalize these findings, a detailed post-processing microstructural analysis of the pre-shocked material is employed. The results obtained suggest that fused silica pre-shocked with shockwaves of sufficient strength retain some memory/embryos of stishovite, and these embryos facilitate stishovite formation during the subsequent ballistic impact.

Application of the materials-by-design approach to armor-grade polymer-matrix composites for enhancement of ballistic-penetration resistance

Purpose – Fiber-reinforced armor-grade polymer-matrix composite materials with a superior penetration resistance are traditionally developed using legacy knowledge and trial-and-error empiricism. This approach is generally quite costly and time-consuming and, hence, new (faster and more economical) approaches are needed for the development of high-performance armor-grade composite materials. One of these new approaches is the so-called materials-by-design approach. Within this approach, extensive use is made of the computer-aided engineering (CAE) analyses and of the empirically/theoretically established functional relationships between an armor-grade composite-protected structure, the properties of the composite materials, material microstructure (as characterized at different length-scales) and the material/structure synthesis and fabrication processes. The paper aims to discuss these issues. Design/methodology/approach – In the present work, a first step is made toward applying the materials-by-design approach to the development of the armor-grade composite materials and protective structures with superior ballistic-penetration resistance. Specifically, CAE analyses are utilized to establish functional relationships between the attributes/properties of the composite material and the penetration resistance of the associated protective structure, and to identify the combination of these properties which maximize the penetration resistance. In a follow-up paper, the materials-by-design approach will be extended to answer the questions such as what microstructural features the material must possess in order for the penetration resistance to be maximized and how such materials should be synthesized/processed. Findings – The results obtained show that proper adjustment of the material properties results in significant improvements in the protective structure penetration resistance. Originality/value – To the authors’ knowledge, the present work is the first reported attempt to apply the materials-by-design approach to armor-grade composite materials in order to help improve their ballistic-penetration resistance.

Ballistic Impact Behavior of Nacre-Like Laminated Composites Consisting of B4C Tablets and Polyurea Matrix

A nacre-like composite armor consisting of B4C tablets and polyurea matrix is modeled, and its ballistic impact behavior and penetration resistance (under a normal and a 15°-oblique impact by a solid right circular cylindrical projectile) were analyzed using a series of transient, nonlinear dynamic, finite-element analyses. Nacre is a biological material constituting the innermost layer of the shells of gastropods and bivalves. It consists of polygonal tablets of aragonite, tessellated to form individual layers and having the adjacent layers as well as the tablets within a layer bonded by a biopolymer. Due to its highly complex hierarchical microstructure, nacre possesses an outstanding combination of mechanical properties, the properties which are far superior to the ones that are predicted using the homogenization techniques such as the rule of mixtures. The results of the transient nonlinear dynamic analysis pertaining to the ballistic impact response and the penetration resistance of the modeled nacre-like armor are compared with their counterparts for the B4C single-block armor having an identical areal density. Furthermore, the effect of various nacre microstructural features (e.g., surface profiling, micron-scale asperities, mineral bridges between the overlapping tablets lying in adjacent layers) on the ballistic penetration resistance of the nacre-like composite armor is investigated in order to identify an optimal nacre-like composite-armor architecture having the largest penetration resistance. The results obtained clearly show that a nacre-like armor possesses a superior penetration resistance relative to its monolithic counterpart, and that the nacre microstructural features considered play a critical role in the armor penetration resistance.

Nacre-like ceramic/polymer laminated composite for use in body-armor applications

Nacre is a biological material constituting the innermost layer of the shells of gastropods and bivalves. It consists of polygonal tablets of aragonite, tessellated to form individual layers and having the adjacent layers as well as the tablets within a layer bonded by a biopolymer. Due to its highly complex hierarchical microstructure, nacre possesses an outstanding combination of mechanical properties, the properties which are far superior to the ones that are predicted using the techniques such as the rule of mixture. In the present work, an attempt is made to model a nacre-like composite armor consisting of boron carbide (B4C) tablets and polyurea tablet/tablet interfaces. The armor is next investigated with respect to impact by a solid right-circular-cylindrical rigid projectile, using a transient non-linear dynamics finite element analysis. The ballistic-impact response and the penetration resistance of the armor is then compared with that of the B4C monolithic armor having an identical areal density. Furthermore, the effect of various nacre microstructural features (e.g. surface profiling, micron-scale asperities, mineral bridges between the overlapping tablets lying in adjacent layers, and B4C nano-crystallinity) on the ballistic-penetration resistance of the composite-armor is investigated in order to identify an optimal nacre-like composite-armor architecture having the largest penetration resistance. The results obtained clearly show that a nacre-like armor possesses a superior penetration resistance relative to its monolithic counterpart, and that the nacre microstructural features considered play a critical role in the armor penetration resistance.

The effect of fused-silica pre-shocking on its devitrification propensity and ballistic resistance: an all-atom molecular-level analysis

Recent studies have suggested that impact-induced devitrification of fused silica, or more specifically formation of high-density stishovite, can significantly improve ballistic-penetration resistance of fused silica, the material which is used in transparent armor. The studies have also shown that in order for stishovite to form during a ballistic-impact event, very high projectile kinetic energy normalized by the projectile/fused-silica target-plate contact area must accompany such an event. Otherwise fused-silica devitrification, if taking place, does not substantially improve the material ballistic-penetration resistance. In the present work, all-atom molecular-level computations are carried out in order to establish if pre-shocking of fused-silica target-plates (to form stishovite) and subsequent unloading (to revert stishovite to the material amorphous structure) can increase fused silica’s propensity for stishovite formation during a ballistic impact. Towards that end, molecular-level computational procedures are developed to simulate both the pre-shocking treatment of the fused-silica target-plate and its subsequent impact by a solid right-circular cylindrical projectile. The results obtained clearly revealed that when strong-enough shockwaves are used in the fused-silica target-plate pre-shocking procedure, the propensity of fused silica for stishovite formation during the subsequent ballistic impact is increased, as is the associated ballistic-penetration resistance. To rationalize these findings, a detailed post-processing microstructural analysis of the pre-shocked material is employed. The results obtained suggest that fused silica pre-shocked with shockwaves of sufficient strength retain some memory/embryos of stishovite, and these embryos facilitate stishovite formation during the subsequent ballistic impact.

The Effect of High-Pressure Devitrification and Densification on Ballistic-Penetration Resistance of Fused Silica

Recent experimental and molecular-level computational analyses have indicated that fused silica, when subjected to pressures of several tens of GPa, can experience irreversible devitrification and densification. Such changes in the fused-silica molecular-level structure are associated with absorption and/or dissipation of the strain energy acquired by fused silica during high-pressure compression. This finding may have important practical consequences in applications for fused silica such as windshields and windows of military vehicles, portholes in ships, ground vehicles, spacecraft, etc. In the present work, our prior molecular-level computational results pertaining to the response of fused silica to high pressures (and shear stresses) are used to enrich a continuum-type constitutive model (that is, the so-called Johnson-Holmquist-2, JH2, model) for this material. Since the aforementioned devitrification and permanent densification processes modify the response of fused silica to the pressure as well as to the deviatoric part of the stress, changes had to be made in both the JH2 equation of state and the strength model. To assess the potential improvements in respect to the ballistic-penetration resistance of this material brought about by the fused-silica devitrification and permanent densification processes, a series of transient non-linear dynamics finite-element analyses of the transverse impact of a fused-silica test plate with a solid right-circular cylindrical steel projectile were conducted. The results obtained revealed that, provided the projectile incident velocity and, hence, the attendant pressure, is sufficiently high, fused silica can undergo impact-induced devitrification, which improves its ballistic-penetration resistance.

Numerical study of mechanisms to minimize failure in a metal with soft backing under plane shock loading

In recent times, several experimental studies have reported improved ballistic penetration resistance and blast survivability of metallic structures to which an external coating of a soft elastomeric material has been applied. This work is aimed at understanding, through numerical simulations on a simple metal/elastomer flat plate geometry subjected to planar blast waves, the detailed mechanics of wave propagation, damage evolution and mitigation in a bilayer system. Void nucleation, growth and coalescence is assumed to be the damaging mechanism in the metal. A meshless technique based on smoothed particle hydrodynamics is used within the framework of large deformation elasto-viscoplasticity in the metal and nonlinear elasticity in the elastomer. We show that the thickness of the elastomer plays an important role in shielding void activity in the metal, by creating a sequence of closely spaced pulses that reflect from the interface and free surfaces to maintain non-tensile or weakly tensile states of stress. Moreover, a fictitious material that is capable of undergoing a transformation to a harder material under pressure is studied that proves to be an ideal candidate for damage mitigation.

Application of Neural Network in the Design of Polymer-Matrix Composites Having Enhanced Ballistic-Penetration Resistance

Application of Neural Network in the Design of Polymer-Matrix Composites Having Enhanced Ballistic-Penetration Resistance

Ballistic performance of titanium alloy encapsulated ceramic composite plates

Titanium alloy (Ti–6Al–4V) encapsulated ceramic (SiC) composite plates were fabricated using graphite mould casting. The ballistic penetration resistance of the plate was evaluated experimentally using a ballistic rifle. Numerical simulations using the finite element method were also conducted to predict the ballistic resistance. The underlying mechanisms were explored in terms of local stress distribution, energy absorption, ballistic limit velocity and obliquity effect. The influence of structural confinement and metal–ceramic interfaces on the overall ballistic performance of the plate was discussed.

Molecular- and domain-level microstructure-dependent material model for nano-segregated polyurea

Purpose – Polyurea is an elastomeric two-phase co-polymer consisting of nanometer-sized discrete hard (i.e. high glass transition temperature) domains distributed randomly within a soft (i.e. low glass transition temperature) matrix. A number of experimental investigations reported in the open literature clearly demonstrated that the use of polyurea external coatings and/or internal linings can significantly increase blast survivability and ballistic penetration resistance of target structures, such as vehicles, buildings and field/laboratory test-plates. When designing blast/ballistic-threat survivable polyurea-coated structures, advanced computational methods and tools are being increasingly utilized. A critical aspect of this computational approach is the availability of physically based, high-fidelity polyurea material models. The paper aims to discuss these issues. Design/methodology/approach – In the present work, an attempt is made to develop a material model for polyurea which will include the eff...