Influence of aluminum alloys on protection performance of metal matrix composite armor reinforced with ceramic particles under ballistic impact

In this research, the ballistic performance of three series of aluminum alloys in the ceramic-reinforced metal matrix composite plates is investigated for protecting against 7.62 × 39 mm bullet. Twenty seven numerical models of the target combinations are provided by ABAQUS FE code to determine the best armor characteristics and confirmed by three experimental ballistic tests. The parameters which considered in this study are aluminum alloys: AA6061, AA7075 and AA5083 as the matrix, alumina ball weight percentages include 15%, 30% and 45% as reinforcements and the target thickness 20, 25 and 30 mm and the effects of these parameters on the ballistic behavior of the composite armor like depth of penetration, residual velocity, kinetic energy and erosion of the projectile are investigated. The results show that AA6061 is the weakest aluminum alloy for ballistic applications and AA5083 is the best choice to use as the aluminum matrix. Also, it's found that the optimum design of aluminum matrix composite armor against 7.62 × 39 mm projectile is AA5083 with 25 mm thickness and 30% alumina.     

A metal/UHMWPE/SiC multi-layered composite armor against ballistic impact of flat-nosed projectile

A novel multi-layered composite armor system is proposed for ballistic protection in the present study. The composite armor is composed of a ductile metal front, followed by a ceramic/UHMWPE laminate composite as the intermediate layer, and a ductile metal back layer. The ballistic performance of the composite armor against flat-nosed projectile was investigated experimentally and numerically. Experimental results show that the proposed composite armor exhibited several failure modes, including ductile hole enlargement of metallic face sheets, fragmentations and cracks of the ceramic layer, delamination, fiber fracture and bulge deformation of UHMWPE laminates. Three-dimensional numerical model was established to analyze the evolution of the whole ballistic response, and to discuss the effect of the ceramic layer placement and the mass allocation between the ceramic layer and UHMWPE laminate layer on the ballistic performance. Simulation results reveal the evident reduction in residual velocity that results from the optimal placement of the ceramic layer. Good balance among the contributions of the target components can be achieved to maximize the total energy absorption of composite armor by optimizing the ceramic placement strategy. The projectile residual velocity and the total energy absorption are insensitive to the mass ratio of ceramic layer to UHMWPE laminate layer within a certain range. Under the condition of a higher mass ratio, the specific energy absorption of UHMWPE layer can be significantly improved due to the full development of its bulging deformation. Consequently, it would benefit the energy absorption capability of the composite armor.     

An experimental investigation on ballistic efficiency of silica-based crosslinked aerogels in aramid fabric

The ballistic performance of crosslinked aerogels which were synthesized using a micelle swelling and structure directing agent against Level IIIA threat was experimentally investigated in this study. Firstly, silica-based aerogels were synthesized in a small scale, and then, isocyanate crosslinking was applied to them. According to the characterization results, the best sample with a desired pore structure for energy absorption was determined. Then, scale-up manufacturing was realized for this sample to use in ballistic tests. Subsequently, neat aramid fabrics with different numbers of layers were tested, and back-face deflection values were determined. The neat aramid fabrics with 24, 30 and 36 layers were deflected as 57.32, 43.58 and 40.38 mm, respectively. To understand the efficiency of the crosslinked aerogel sample, it was placed into the 30 layers of the aramid fabric as the back-face deflection value of its neat form was closest to the critical back face deflection value which is defined in the related standard. Three types of aerogel monoliths, as rectangular, large diameter of circular and small diameter of circular were tested with aramid fabrics. Fewer fabrics were perforated at the rate of 72% in all ballistic test samples including aerogel monoliths in comparison to the neat aramid fabric tests. 7 or 8 layers of fabric were perforated in the test of the neat aramid fabric samples, while 2 layers of fabric were perforated in the samples containing aerogel.     

Promising curaua fiber‐reinforced polyester composite for high‐impact ballistic multilayered armor

A typical multilayered armor system (MAS) is composed of a harder front ceramic tile, which is able to erode heavy ammunition, such as the 7.62 mm bullet, followed by a second layer to further reduce the impact energy. Aramid fabric is a common choice for the second layer. In the present work, polyester matrix composites reinforced with 10 to 30 vol% of curaua fibers, despite having much lower strength and stiffness than aramid fabric, displayed similar trauma indentation in a standard clay witness simulating the human body. Impedance matching and scanning electron microscopy analyses suggest effective energy absorption through ceramic fragment capture by curaua composites. Additionally, because of the high cost of aramid fabric, a full MAS with curaua fiber composite is much cheaper than a MAS composed of aramid fabric. Taking into consideration, both the economical and environmental advantages of natural fibers, it is concluded that curaua fiber‐reinforced polyester composite could replace aramid fabric as the second layer in MASs for personal ballistic protection. POLYM. ENG. SCI., 57:947–954, 2017. © 2016 Society of Plastics Engineers     

Preparation and properties of a p‐aramid fabric composite impregnated with a magnetorheological fluid for body armor applications

A polyurethane (PU)‐magnetorheological fluid (MRF)/p‐aramid fabric composite was fabricated, and its mechanical properties were subsequently investigated. The contribution of the PU‐MRF matrix to the impact resistance of the system was then discussed. MRFs consist of stable suspensions of magnetite particles within a carrying fluid. Therefore, when an external magnetic field is applied, the MRFs exhibit drastic and reversible changes in rheological properties as a result of the field‐induced ordering of the particulate phase. We then attempted to develop new and enhanced bulletproof materials by incorporating MRF and PU in a p‐aramid fabric. It was found that when a magnetic field was applied, the mechanical properties of the PU‐MRF/p‐aramid fabric composite improved. It was also found that adding a PU matrix improves the impact performance of the PU‐MRF/p‐aramid fabric composite, relative to a neat p‐aramid fabric and a MRF/p‐aramid fabric composite with similar areal density. The improved impact performance of the PU‐MRF/p‐aramid fabric composite appears to be because the PU film and MRF enable different energy absorbing mechanisms, including particle friction, fabric/matrix debonding, matrix cracking, and delamination, which are not observed in neat p‐aramid fabric systems. The findings of this study are thought to be important from a design viewpoint of soft armors. POLYM. ENG. SCI., 55:729–734, 2015. © 2013 Society of Plastics Engineers     

Enhancement in ballistic performance of composite hard armor through carbon nanotubes

The use of carbon nanotubes in composite hard armor is discussed in this study. The processing techniques to make various armor composite panels consisting of Kevlar^®29 woven fabric in an epoxy matrix and the subsequent V50 test results for both 44 caliber soft-point rounds and 30 caliber FSP (fragment simulated projectile) threats are presented. A 6.5% improvement in the V50 test results was found for a combination of 1.65 wt% loading of carbon nanotubes and 1.65 wt% loading of milled fibers. The failure mechanism of carbon nanotubes during the ballistic event is discussed through scanning electron microscope images of the panels after the failure. Raman Spectroscopy was also utilized to evaluate the residual strain in the Kevlar^®29 fibers post shoot. The Raman Spectroscopy shows a Raman shift of 25 cm^?1 for the Kevlar^®29 fiber utilized in the composite panel that had an enhancement in the V50 performance by using milled fiber and multi-walled carbon nanotubes. Evaluating both scenarios where an improvement was made and other panels without any improvement allows for understanding of how loading levels and synergistic effects between carbon nanotubes and milled fibers can further enhance ballistic performance.     

Analysis of the temperature rise in the projectile and extended chain polyethylene fiber composite armor during ballistic impact and penetration

The ultra-high strength/modulus, extended chain polyethylene fiber (Spectra® fiber) composite has shown great potential as a lightweight armor material with its extraordinary capability of absorbing the kinetic energy of projectiles. But the relatively low melting point of this fiber (～ 145°C) has caused concerns regarding the effect of temperature rise during the impact/penetration process on the performance as armor material. In this article, an analysis of temperature rise in projectile and the fiber composite during the impact/penetration process is described. Combining the simulation of impact deformation by finite element analysis and the simulation of temperature rise by a finite difference approximation of the related dynamic equations, the temperature rise caused by the projectile/composite interaction was estimated. Results show that there is a significant temperature rise at the projectile/composite interface due to the friction but that the short length of time involved in the process and the low thermal conductivity of Spectra fiber composite keep the temperature rise in a very small region (in the order of 0.001 cm) around the interface during the impact/penetration process. Consequently, the volume that is affected by the temperature rise is very small, in the order of total 0.001 cm³ around the projectile, and this is too small to generate any detectable effect on the armor performance. After the projectile is stopped, however, substantial heating of fiber composite can occur under specific conditions as the result of heat flow from the hot projectile embedded in the composite. This heating of fibers, however, is a postmortem effect and hence inconsequential to the ballistic performance of the composite armor.     

Multiple ballistic damage of segmented SiC/BN laminated ceramic composite armor

This article investigated the structure of the laminated ceramics to improve the multiple ballistic performance of segmented ceramic composite armors. The multiple ballistic experiments were conducted with 5.8 mm caliber steel core bullets at the impact velocity of about 920 m/s. The experiments verified that two laminated SiC/BN structures (GLC and ULC) exhibit higher residual ballistic performances than the monolithic SiC structure (MC). Moreover, through damage evolution analysis, two laminated SiC/BN structures (GLC and ULC) exhibit less sensitivity to the multiple ballistic impacts damages, and possess more energy absorption mechanisms than the monolithic ceramics. The structure design of the laminated of ceramics is beneficial for improving the multiple ballistic performances of composite armors and reducing the crater deformation.     

Effect of interlaminar toughness on the low‐velocity impact damage in composite laminates

Based on the continuum damage mechanics (CDM) and the cohesive zone model (CZM), a numerical analysis method for the evaluation of damage in composite laminates under low‐velocity impact is proposed. The intraply damage including matrix crack and fiber fracture is represented by the CDM which takes into account the progressive failure behavior in the ply, using the damage variable to describe the intraply damage state. The delamination is characterized by a special contact law including the CZM which takes into account the normal crack and the tangential slip. The effect of the interlaminar toughness on the impact damage is investigated, which is as yet seldom discussed in detail. The results reveal that as the interlaminar fracture toughness enhances, the delamination area and the dissipated energy caused by delamination decrease. The contribution of normal crack and tangential slip to delamination is evaluated numerically, and the later one is the dominant delamination type during the impact process. Meanwhile, the numerical prediction has a good agreement with the experimental results. The study is helpful for the optimal design and application of composite laminates, especially for the design of interlaminar toughness according to certain requirements. POLYM. COMPOS. 37:1085–1092, 2016. © 2014 Society of Plastics Engineers     

穿透裂纹对层合板拉伸性能的影响

对含3种不同方向穿透裂纹的层合板进行了拉伸试验研究,通过观测试验过程与断口分析,研究了含穿透裂纹层合板的失效行为。在此基础上,采用ABAQUS软件建立了含穿透裂纹层合板渐进损伤有限元分析模型,对其拉伸性能进行了分析,并对初始损伤与裂纹扩展路径进行了研究,讨论了裂纹形式对复合材料层合板剩余拉伸强度的影响。结果表明,初始损伤发生在裂纹尖端,损伤有沿垂直于载荷方向扩展的趋势。裂纹方向的变化对层合板的剩余强度有明显影响。     

Study on ballistic mechanism of B4C/Al gradient armor

In order to improve the anti-penetration performance of gradient armor, the constitutive models of B₄C/Al composites with different compositions were determined according to the bending curves. The anti-bullet simulation of B₄C/Al gradient armor was carried out by ANSYS-DYNA finite element software, and the stress state of B₄C/Al gradient material under 7.62-mm bullet penetration was analyzed. Meanwhile, the propagation law of stress wave in armor was studied by Hopkinson bar simulation and the improved internal stress wave model, which further revealed the ballistic mechanism of B₄C/Al gradient armor. The simulation results showed that, compared with the traditional laminated armor, the toughness of B₄C/Al gradient armor material increased with the change of layer thickness, resulting in the fact that the whole armor could withstand greater stress without breaking, and the anti-penetration time was prolonged. In addition, the performance difference between the layers of the gradient armor was slight, and the spallation phenomenon of the relative double-layer armor decreases, which enhanced the multiple hit performance of the armor and the absorption capacity of the stress wave. The performance of B₄C/Al gradient armor specimens and double-layer specimens were tested by drop hammer impact test. The test results were consistent with the simulation results.     

Interlaminar fracture toughness of selectively stitched thick carbon fibre reinforced polymer fabric composite laminates

Abstract

Carbon fibre reinforced polymer fabric specimens prepared from selectively stitched thick laminates have been tested under mode I (tension) and mode II (shear) loading, similar to already established tests used for thin unidirectional specimens. The respective interlaminar fracture toughness characteristics were derived for laminates of different stitching configurations. Results indicated significant interlaminar fracture toughness increase for all stitched samples compared with non-stitched samples, especially under mode I loading. It was concluded from parametric investigations that carbon thread stitching is more effective than its aramid counterpart in improving interlaminar fracture toughness. This is attributable to its higher stiffness and better bonding to the carbon fibre reinforced polymer system compared with the aramid thread.     

Interlaminar fracture toughness of woven fabric composite laminates with carbon nanotube/epoxy interleaf films

The Mode I interlaminar fracture behavior of woven carbon fiber/epoxy composite laminates incorporating partially cured carbon nanotube/epoxy composite films has been investigated. Laminates with films containing carbon nanotubes (CNTs) in the as‐received state and functionalized with polyamidoamine were evaluated, as well as laminates with neat epoxy films. Double‐cantilever beam (DCB) specimens were used to measure G_Ic, the critical strain energy release rate (fracture toughness) versus crack length. Post‐fracture microscopic inspection of the fracture surfaces was performed. Results show that initial fracture toughness was improved with the amino‐functionalized CNT/epoxy interleaf films, but the important factor appears to be the polyamidoamine functionalization, not the CNTs. The initial fracture toughness remained relatively unaffected with the incorporation of neat epoxy and as‐received CNT/epoxy interleaf films. Plateau fracture toughness was unchanged with the use of functionalized CNT/epoxy interleaf films, and was reduced with the use of neat epoxy and as‐received CNT/epoxy interleaf films. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Role of carbon nanotubes in the ballistic properties of boron carbide/carbon nanotube/ultrahigh molecular weight polyethylene composite armor

Composite armor panels with boron carbide ceramic as striking face, backed with carbon nanotube-ultra high molecular weight polyethylene (CNT-UHMWPE), have been fabricated as lightweight body armors. The armor panels were tested against actual ammunitions through self-loading rifle (SLR) and AK-47. Slip lines were observed in boron carbide with high energy bullets. CNT-UHMWPE composite backing resulted in a low back face signature (BFS) due to the formation of a strong bond between CNT and UHMWPE and high energy dissipation through this composite. The role of CNT in the ballistic protection of this composite armor has been explained with the help of necessary characterization by electron microscopy, X-ray radiography, Fourier transformed infrared spectroscopy and differential scanning calorimetry.     

冲击位置对挖补修理层合板冲击后压缩性能的影响

使用过程中的低速冲击损伤对修理后的复合材料结构同样会造成威胁.设计并进行了复合材料挖补修理结构的低速冲击及冲击后压缩试验,测量了试验件的损伤投影面积和剩余压缩强度,分析了不同冲击位置的影响.结果表明,挖补修理层合板冲击后压缩强度比未修补板的低,挖补层合板对低速冲击位置较为敏感.冲击点离开挖补区一定距离后,挖补对层合板的低速冲击及其继后压缩性能的影响消失.     

Instrumented puncture impact characterization of composite laminates for printed circuit board applications

One sided copper glass/epoxy laminates for printed circuit board (PCB) applications were examined using an instrumented puncture impact technique. The effect of the diameter of the support ring, the initial impact velocity, and the preence of a stress concentrator on the impact parameters were evaluated. The orientation of the copper film with respect to the impacter was also varied. The PCB laminate showed brittle failure under the different conditions examined. Results showed that a higher degree of toughness was found for the condition where the copper layer was directly impacted by the dart. The maximum force and the total impact energy were found to be independent of the strain rate. The effect of a stress concentrator on the impact parameters was also found to be minimial. Total impact energies were found to be in the range of 8.8 to 12.6 J for the different testing conditions.     

中温固化环氧/杂环芳纶（布）预浸料及其复合材料性能研究

试验研究了044B杂环芳纶布性能、3233/044B预浸料制备及其复合材料力学性能.结果表明,044B杂环芳纶布性能较好,3233/044B复合材料的常规性能和耐热性较好,夹层结构的滚筒剥离强度高,树脂具有韧性,适用于复合材料夹层结构.该预浸料已用于航空复合材料制件.