Advanced layered personnel armor

Utilizing shock compression physics considerations and explicit numerical techniques a methodology has been developed to design composite personnel armor by optimizing the role each layer plays during projectile defeat. The initial design consists of a very hard 1st layer to deform and fracture the projectile, an orthotropic 2nd layer to slow down the shock wave propagation in the through thickness direction, whilst allowing rapid propagation in the transverse directions, a 3rd porous layer to absorb the shock wave energy through PV-work, and a 4th layer to provide confinement for the porous medium. Based on the above armor protection concept, composite plates comprising of alumina (Al₂O₃) Ceramic, Dyneema^® HB25 and porous polyurethane (PU) foam were constructed to test against baseline armor AISI 4140 steel plate. A hypothetical orthotropic material model closely resembling that of Dyneema HB25 was derived based on fundamental materials relations as well as limited available literature information. Material models for the other materials used in this research were based on existing sources. An integral experiment was conducted to validate this composite armor against numerical simulations. Through this study, the composite armor has been shown experimentally to be more effective in resisting penetration than a steel plate of equivalent (and slightly greater) areal density, and that the material layering sequence is fundamentally correct, while the numerical modeling has provided a general guidance to the behavior of the system. This research was done to explore this kind of approach to armor design to evaluate its merit. We make no claim that this design is ready for field use.     

Ballistic-performance optimization of a hybrid carbon-nanotube/E-glass reinforced poly-vinyl-ester-epoxy-matrix composite armor

The material model for a multi-walled carbon nanotube (MWCNT) reinforced poly-vinyl-ester-epoxy matrix composite material (carbon nanotube reinforced composite mats, in the following) developed in our recent work (M. Grujicic et al. submitted), has been used in the present work within a transient non-linear dynamics analysis to carry out design optimization of a hybrid polymer-matrix composite armor for the ballistic performance with respect to the impact by a fragment simulating projectile (FSP). The armor is constructed from E-glass continuous-fiber poly-vinyl-ester-epoxy matrix composite laminas interlaced with the carbon nanotube reinforced composite mats. Different designs of the hybrid armor are obtained by varying the location and the thickness of the carbon nanotube reinforced composite mats. The results obtained indicate that at a fixed thickness of the armor, both the position and the thickness of the carbon nanotube reinforced composite mats affect the ballistic performance of the armor. Specifically, it is found that the best performance of the armor is obtained when thicker carbon nanotube reinforced composite mats are placed near the front armor face, the face which is struck by the projectile. The results obtained are rationalized using an analysis of the elastic wave reflection and transmission behavior at the lamina/met and laminate/air interfaces.     

Ballistic protection performance of curved armor systems with or without debondings/delaminations

In order to discern how pre-existing defects such as single or multiple debondings/delaminations in a curved armor system may affect its ballistic protection performance, two-dimensional axial finite element models were generated using the commercial software ANSYS/Autodyn. The armor systems considered in this investigation are composed of boron carbide front component and Kevlar/epoxy backing component. They are assumed to be perfectly bonded at the interface without defects. The parametric study shows that for the cases considered, the maximum back face deformation of a curved armor system with or without defects is more sensitive to its curvature, material properties of the ceramic front component, and pre-existing defect size and location than the ballistic limit velocity. Additionally, both the ballistic limit velocity and maximum back face deformation are significantly affected by the backing component thickness, front/backing component thickness ratio and the number of delaminations.     

层间混杂复合材料装甲板防弹性能及其防弹机制

为研究层间混杂复合材料装甲板的防弹性能及其防弹机制,采用钢芯弹侵彻层间混杂复合材料装甲板。以超高分子量聚乙烯（Ultra high molecular weight polyethylene,UHMWPE）纤维、对位芳香族聚酰胺纤维作增强纤维,水性聚氨酯（Waterborne Polyurethane,WPU）树脂和环氧树脂（Epoxy resin,EP）作基体,采用热压工艺制备单向（Unidirectional,UD）结构的层间混杂复合材料装甲板。研究混杂比例、防弹面和树脂基体对混杂复合材料装甲板防弹性能的影响以及弹击后混杂复合材料装甲板的破坏形貌,分析混杂复合材料装甲板的防弹机制,并对复合材料装甲板的破坏机制进行了分析。结果表明:混杂复合材料装甲板的防弹性能优于其任一单一纤维复合材料装甲板;WPU的防弹性能要优于环氧树脂;以UHMWPE纤维复合材料充当防弹面时,混杂复合材料装甲板具有更好的防弹性能;纤维拉伸变形和装甲板分层是纤维复合材料装甲板主要的吸能方式。      

陶瓷复合装甲优化设计及弹击后剩余弯曲强度

根据防护要求和防护机制,设计了一种C/C-SiC陶瓷/铝基复合泡沫复合装甲。在确保复合装甲面密度为44 kg/m²的前提下,以弹击后剩余弯曲强度为评价标准,以陶瓷板布置位置、各组成层厚度、泡沫金属中泡沫孔径尺寸为研究因素,设计了三因素三水平的正交模拟优化方案,利用有限元软件ABAQUS模拟了子弹侵彻陶瓷靶板的过程及弹击损伤后复合装甲的弯曲实验过程,预测了剩余弯曲强度,并进行了结构优化。根据数值模拟结果制备陶瓷复合装甲试样,进行实弹打靶和弯曲实验以验证复合装甲试样剩余弯曲强度。结果表明,以MIL-A-46103E Ⅲ类2A级为防护标准,剩余弯曲强度最高的陶瓷复合装甲最优化结构形式为：陶瓷板厚度12 mm、陶瓷板做防弹面板、Al基复合泡沫孔径为4 mm+10 mm的混合;对剩余弯曲强度的主次影响因素排序为：陶瓷板厚度>陶瓷板布置位置>Al基复合泡沫孔径。     

多层异质复合结构的动力学响应及抗侵彻性能

为研究多层异质复合结构动力学响应及抗侵彻性能,利用霍普金森试验装置,对不同材料排布顺序及含泡沫铝夹芯的多层复合结构进行冲击加载,通过贴在入射杆和透射杆上的应变片测得入射波、反射波、透射波波形,验证数值仿真模型正确性;结合数值模拟,研究不同结构对试件内部应力波传播特性和应力场分布影响规律;依据复合结构动力学响应特征,设计复合靶板并进行抗侵彻试验,分析靶板塑性变形特征及抗侵彻耗能机制;通过数值模拟分析泡沫铝夹芯厚度对防护性能影响。结果表明,装甲钢后置复合结构及含泡沫夹芯结构有助于减缓应力集中,减小陶瓷损伤面积;泡沫铝夹芯过厚难以为靶板变形提供支撑,降低抗侵彻阻力;五种夹芯厚度h=2 mm、h=5 mm、h=10 mm、h=20 mm、h=30 mm中,h=10 mm对应多层异质复合靶防护性能最优。      

Ballistic impact performance of an armor material consisting of alumina and dual phase steel layers

Utilization of a ceramic front layer provides an improvement in the ballistic efficiency of monolithic metallic materials. In the current paper, the ballistic behavior of laminated composite having alumina front and dual phase steel backing layers was studied using 7.62 mm armor piercing (AP) projectiles under normal impact. The variables used were martensite content of the backing layer and the areal density of the composite. Experimental results showed that utilization of a 6 mm thick alumina front layer which was bonded to dual phase steel enhanced the ballistic resistance of the dual phase steel remarkably.     

Affordable processing of thick section and integral multi-functional composites

The use of multi-functional integral armor is of current interest in armored vehicles and military carriers. In the present study, thick-section laminated composites and multi-layered integrated composites have been processed/manufactured with the aim of providing multi-functionality including easy reparability, quick deployment, enhanced ballistic damage and fire protection, as well as lightweight advantages. The design of an integral armor utilizes a combination of thick-section structural composite, ceramic tiles, resilient rubber, fire retardant laminate liner and a composite durability cover. Processing techniques such as automated fiber placement and/or autoclave molding are traditionally used to process dissimilar multi-layered structure, but prove to be expensive.This work focuses on emerging cost-effective liquid molding processes such as vacuum assisted resin transfer/infusion molding (VARTM) for the production of thick-section and integral armor parts (up to 50 mm thick). While thick-section composites have applications in a variety of structures including armored vehicles, marine bodies, civil infrastructure, etc. in the present work they refer to the structural laminate within the integral armor. The processing steps of thick-section composite panels and integral armor have been presented. The integrity of the interfaces has been evaluated through scanning electron microscopy (SEM). Representative results on static and dynamic response (high strain rate, HSR and ballistic impact) of the VARTM processed thick-section composite panels are presented. Wherever applicable, comparisons are made to conventional closed-mold resin transfer molding (CMRTM). Process sensing by way of flow and cure monitoring of the resin in the fiber perform has been conducted using embedded direct current (DC)-based sensors in the thick-section preform and integral armor interfaces. The feasibility of cost-effective VARTM for producing thick-section composites and integral armor has been demonstrated.     

结构形式对舰船舷侧复合装甲结构抗穿甲性能的影响研究

为探讨结构形式对舰船舷侧复合装甲结构抗穿甲性能的影响,采用均质钢板前置和后置复合材料板分别模拟舰船舷侧外设和内设复合装甲结构,结合低速弹道冲击实验,分析和比较了两种结构形式组合靶板的穿甲破坏模式和抗弹吸能能力。在此基础上,得到了球头弹穿透后置组合靶板的剩余速度理论预测公式,并与试验结果进行了比较。结果表明,两种组合靶板中复合装甲板破坏模式的差异主要体现在迎弹面纤维剪切断裂的程度,而均质钢板则由于复合装甲板的影响,呈现出完全不同的破坏模式;后置组合靶板的抗弹吸能能力要大于前置组合靶板;将弹丸穿透后置组合靶板的剩余速度理论预测值与实验结果进行比较,两者吻合较好。     

Numerical simulation of ceramic composite armor subjected to ballistic impact

Armor systems made of ceramic and composite materials are widely used in ballistic applications to defeat armor piercing (AP) projectiles. Both the designers and users of body armor face interesting choices – how best to balance the competing requirements posed by weight, thickness and cost of the armor package for a particular threat level. A finite element model with a well developed material model is indispensible in understanding the various nuances of projectile–armor interaction and finding effective ways of developing lightweight solutions. In this research we use the explicit finite element analysis and explain how the models are built and the results verified. The Johnson–Holmquist material model in LS-DYNA is used to model the impact phenomenon in ceramic material. A user defined material model is developed to characterize the ductile backing made of ultra high molecular weight polyethylene (UHMWPE) material. An ad hoc design optimization is carried out to design a thin, light and cost-effective armor package. Laboratory testing of the prototype package shows that the finite element predictions of damage are excellent though the back face deformations are under predicted.     

Effect of interlayer on stress wave propagation in CMC/RHA multi-layered structure

Due to the significance of the propagation of stress wave in composite armor during projectile–target interaction, the characteristics of stress wave propagation in multi-layered composite structure under impact load were investigated by traditional Split Hopkinson Pressure Bar system in this study. The effect of interlayer characteristic on the stress wave propagation was discussed. The results show that the interlayer properties between CMC and RHA steel play an important role in the propagation of wave. Compared to “CMC/RHA” structure without interlayer, the tungsten carbide interlayer can increase stress level in CMC layer remarkably, while silica gel layer has an opposite effect, and epoxy resin adhesive layer has no distinct effect on the propagation of stress wave. The increased compressive stress level in CMC layer is very useful when the CMC layer served as the face plate of a composite armor. During the impact process of the projectile to the armor, the anti-penetration capability of the face plate of the composite armor can be improved when in the compression stress state. In the comparison ballistic testing conducted with 7.62 mm armor piercing projectiles, the protection efficiency of the “CMC/WC/RHA” composite armor is about 36% higher than that of the “CMC/RHA” structure, which is in good correlation with the stress wave measurement results.     

The effect of geometric scale on impact induced fragmentation, and its application to the design of dual plate armor

An analysis is presented which predicts that, for a fixed impact velocity, impact induced fragmentation becomes more severe as geometric scale increases. Test data is presented which supports this prediction, and which allows calculation of material dependent coefficients. The analysis was based on a minimization with respect to radius, for an expanding body, of a total energy density term (expansion kinetic energy per unit volume plus surface energy per unit volume). The test configuration was a steel sphere impacting an aluminum plate, with fragmentation recorded by a stack of spaced witness panels. The tests were run at full and half scale. Correlation between testing and analysis was achieved for the number of fragments perforating the front witness panel when a term analogous to a threshold energy was introduced. While the fragment count showed a dependence on geometric scale, the relative depth of penetration (number of witness panels perforated) did not. This suggested that the targets were fragmented, but that the projectile remained in one piece. A reduction in penetration depth with increasing impact velocity was seen, and was attributed to increased projectile deformation. For cases where the projectile would fragment (for example, if a harder target material were used), the effect of geometric scale on the performance of dual plate armor is predicted by analysis. The prediction is that, for impact velocities where projectile breakup at the outer plate of dual plate armor is a factor, the armor required to stop a large scale projectile can be lighter, on a relative basis, than the armor required to stop a small scale projectile.     

Bio-inspired armor protective material systems for ballistic shock mitigation

Severe transient ballistic shocks from projectile impacts, mine blasts, or overhead artillery attacks can incapacitate an occupant at low frequencies, or sensitive equipment at high frequencies, if they are not properly attenuated by armor protective systems. Unique challenges exist in developing armor protective systems for mitigating both low and high frequency ballistic shocks due to the lack of robust design methodology, the severe dynamic loading conditions, and the uncertainties in predicting ballistic shock responses.Nature offers engineers a blueprint of highly effective, efficient, and adaptive material designs to protect certain regions from external threats. This paper presents the modeling, analysis, design, optimization, fabrication, and experimental validation of bone-inspired armor protective material systems for reducing projectile penetrations and alleviating ballistic shocks at both low and high frequencies. The optimized bone-inspired armor protective material system has a soft–stiff–soft–stiff material distribution pattern based on bone-foramen and osteonal-bone material systems. Analysis and experimental results demonstrated that the bone-inspired armor protective material systems have excellent capabilities for drastic ballistic shock mitigation, weight savings, and significant reductions in penetration and load transmission under ballistic loading conditions.     

A unit cell approach of finite element calculation of ballistic impact damage of 3-D orthogonal woven composite

This paper presents ballistic impact damages of 3-D orthogonal woven composite in finite element analysis (FEA) and experimental. A unit-cell model of the 3-D woven composite was developed to define the material behavior and failure evolution. A user-defined subroutine VUAMT was compiled and connected with commercial available FEA code ABAQUS/Explicit to calculate the ballistic penetration. Ballistic impact tests were conducted to investigate impact damage of 3-D kevlar/glass hybrid woven composite. Residual velocities of conically-cylindrical steel projectiles (Type 56 in China Military Standard) and impact damage of the composite targets after ballistic perforation were compared both in theoretical and experimental. The reasonable agreements between FEA results and experimental results prove the validity of the unit-cell model in ballistic limit prediction of the 3-D woven composite. We believe such an effort could be extended to bulletproof armor design with the 3-D woven composite.     

High-velocity plate impact of metal foams

The ballistic impact of a massive, effectively 1-D plate on an initially stationary foam layer is considered. It is shown that four discrete velocity regimes must be considered. Two of these regimes are of major interest for ballistic impact studies. Regime 2 considers the case when the initial velocity of the plate is lower than the sound velocity of the constitutive material of the foam, but higher than the linear sound velocity of foam. Regime 3 considers the case when the initial plate velocity is lower than the linear sound velocity of the foam; but remains higher than the effective sound velocity for a perturbation in which the amplitude lies in the so-called “plateau region” of the static stress–strain diagram.Analytical solutions for dynamic deformation and energy absorption of foam materials under the plate impact condition for Regimes 2 and 3 are developed. It has been shown that in both cases, a compressive shock wave appears. The physical difference between these two regimes entails not only the creation of a shock front associated with the collapsing foam, but also an acoustic precursor in the case of Regime 3. As a result, the efficiency of energy absorption in Regime 2 depends only on the initial density of the foam, the density of the constitutive material of the foam, and the areal mass of the impacting plate, whereas the efficiency of energy absorption for Regime 3 also depends on the Mach number and the critical stress of the foam.Numerical plate impact simulations have been carried out in impact Regime 2. Explicit finite element analysis is performed using LS-DYNA 960. The time history of dynamic deformation and energy of the impact plate is presented. The numerical prediction is found to be in good agreement with the analytical results.     

Dynamic response of aluminum honeycomb sandwich panels under foam projectile impact

The dynamic response of honeycomb sandwich panels under aluminum foam projectile impact was investigated. The different configurations of panels were tested, and deformation/failure modes were obtained. Corresponding numerical simulations were also presented to investigate the energy absorption and deformation mechanism of sandwich panels. Results showed that the deformation/failure modes of sandwich panels were sensitive to the impact velocity and density of aluminum foam. When the panel was impacted by the aluminum foam projectile with the back mass of nylon, the “accelerating impact” stage can be produced and may lead to further compression and damage of the sandwich structures.     

高精度碳纤维增强树脂复合材料夹层天线面板热变形影响参数仿真与实验

为满足亚毫米波、太赫兹波段等高频天线反射面的应用需求,采用附加树脂修型技术制得1米级、面形精度优于10 μm均方差(RMS)的碳纤维增强树脂(CFRP)复合材料天线面板。主要开展了针对高精度CFRP复合材料面板在极端低温环境下的热变形机制研究。根据基础材料性能测试数据,建立面板的有限元仿真模型,预测大温差工况下多结构参数面板的热变形残差,分析了影响面板热变形特性的主要因素。比较了铝蜂窝和碳管阵列夹芯两种面板结构热变形特性的差异。结果表明,碳管夹芯结构面板具备更高的比刚度和热稳定性。通过仿真结构优化给出了面板的结构设计参数,并重新试制了原型面板。采用基于高精度数字摄影测量的实验方法,对铝蜂窝和碳管阵列两种夹芯结构原型面板在低温环境下的热变形误差进行了测量,通过分析实验与仿真结果的误差来源,讨论了有限元预测方法的可行性,给出了针对高精度CFRP复合材料面板设计及工艺方法的指导意见。      

Ballistic resistance of double-layered armor plates

In this paper, the ballistic resistance of double-layered steel shields against projectile impact at the sub-ordnance velocity is evaluated using finite element simulations. Four types of projectiles of different weight and nose shapes are considered, while armor shields consist of two layers of different materials. In a previous study of the same authors, it was shown that a double-layered shield of the same metal was able to improve the ballistic limit by 7.0–25.0% under impact by a flat-nose projectile, compared to a monolithic plate of the same weight. Under impact by a conical-nose projectile, a double-layered shield is almost as capable as a monolithic plate. The present paper extends the analysis to double-layered shields with various metallic material combinations. The study reveals that the best configuration is the upper layer of high ductility and low strength material and the lower layer of low ductility and high strength material. This configuration results in some 25% gain in the ballistic limit under moderate detrimental impact. This research helps clarify the long standing issue of the ballistic resistance of the multi-layered armor configuration.     

纤维增强树脂基复合材料防弹性能影响因素及破坏机制

以超高分子量聚乙烯(Ultra High Molecular Weight Polyethylene,UHMWPE)纤维、S-玻璃纤维、芳纶1414纤维和杂环芳纶纤维增强聚烯烃(Polyolefin,PO)和水性聚氨酯(Waterborne Polyurethane,WPU)树脂,采用热压工艺制备正交单向无纬(UD)结构复合材料装甲板;通过装甲板弹道极限速度测试,研究了纤维增强树脂基复合材料装甲板防弹性能的影响因素;通过体视显微镜观察装甲板侵彻破坏形貌,分析了纤维增强树脂基复合材料的破坏机制。结果表明:UHMWPE纤维增强PO树脂基复合材料的防弹性能与UHMWPE纤维的强度和模量呈正相关,但纤维模量对复合材料防弹性能的影响随着纤维模量的增大而逐渐变弱;在WPU树脂体系下,四种纤维的防弹性能由高到低依次是UHMWPE纤维、杂环芳纶纤维、芳纶1414纤维、S-玻璃纤维;纤维增强树脂基复合材料装甲板中纤维破坏方式有迎弹面纤维被剪切冲塞、中部被纤维拉伸变形后剪切、背弹面纤维被拉伸断裂,中部纤维拉伸变形是消耗子弹动能的主要方式。     

Elastomer–steel laminate armor

Elastomeric coatings have been found to substantially increase the ballistic limit of underlying steel substrates, with an important mechanism being the impact-induced transition of the rubber to the glassy state. A composite array of elastomer–steel panels has been found to further increase the penetration resistance; moreover, the elastomer coating itself can be a laminate structure of soft and hard materials. The requirements for the laminate to function well are that the underlying substrate retains sufficient bending stiffness for the impact to induce the transition of the polymer, which in combination with break up and dissipation of the pressure wave due to impedance mismatching, leads to large increases in ballistic penetration resistance.