Multilayered Armor Research Articles

Numerical and Experimental Study of Hybrid Composite Body Armor

Kevlar is widely used in ballistic applications to protect against hand pistols, due to its high strength, lightweight, and high impact resistance. Compared to other fabrics, Kevlar is considered a typical material due to its strength properties for bullet-proof vests. This project aims to develop a hybrid composite and investigate its behavior under ballistic impact both experimentally and theoretically. Ceramic/woven fabric reinforced epoxy/polycarbonate multilayered armors were developed. The initial layer of defense against the bullet is silicon carbide (SiC). The intermediate composite is made up of aramid fabric (Kevlar) reinforced epoxy (KEV/EPX). The rear layer was made of polycarbonate (PC). A 9 mm FMJ bullet was fired in 310 m/s, towards samples of 900 cm2. To simulate the ballistic test, Ansys Workbench Explicit Dynamics and Ansys AUTODYN 3D were used. An integrated methodological approach of experimentation and simulation was followed to assess the behavior of samples. Obtained results showed that SiC+ KEV/EPX+ polycarbonate was able to stop the 9mm FMJ bullet and indicated that armor layers perforated without penetration. Back Face Signature BFS was also measured, which is within the allowed limit. The ceramic layer absorbs the largest percentage of the overall energy absorbed, compared to fiber-reinforced epoxy and polycarbonate, which reach 77.8% of the entire energy.

Kevlar fabric reinforced polybenzoxazine composites filled with silane treated microcrystalline cellulose in the interlayers: The next generation of multi-layered armor panels

The design of astonishing combinations of benzoxazine resins with various fillers is nowadays of great interest for high quality products, especially in ballistic armors. The objective of this study is to investigate a new hybrid material prepared as multi-layered composite plate by hand lay-up technique. Different composites were manufactured from Kevlar fabrics reinforced polybenzoxazine, which was filled with silane treated microcrystalline cellulose (MCC Si) at various amounts in the interlayers. The developed materials were tested for their flexural, dynamic mechanical and ballistic performance. The aim was to highlight the effect of adding different amounts of MCC Si on the behavior of the different plates. Compared to the baseline, the dynamic mechanical and bending tests revealed an obvious decrease of the glass transition of 21 °C and a notable increase in storage modulus and flexural strength of about 180 %and17%, respectively, upon adding 1% MMC Si as filler. Similarly, the ballistic test exhibited an enhancement in kinetic energy absorption for which the composite supplemented with 1% MCC Si had the maximal energy absorption of 166.60 J. These results indicated that the developed panels, with interesting mechanical and ballistic features, are suitable to be employed as raw materials to produce body armor.

Preparation and Ballistic Performance of a Multi-Layer Armor System Composed of Kevlar/Polyurea Composites and Shear Thickening Fluid (STF)-Filled Paper Honeycomb Panels.

In this study, the ballistic performance of armors composed of a polyurea elastomer/Kevlar fabric composite and a shear thickening fluid (STF) structure was investigated. The polyurea used was a reaction product of aromatic diphenylmethane isocyanate (A agent) and amine-terminated polyether resin (B agent). The A and B agents were diluted, mixed and brushed onto Kevlar fabric. After the reaction of A and B agents was complete, the polyurea/Kevlar composite was formed. STF structure was prepared through pouring the STF into a honeycomb paper panel. The ballistic tests were conducted with reference to NIJ 0101.06 Ballistic Test Specification Class II and Class IIIA, using 9 mm FMJ and 44 magnum bullets. The ballistic test results reveal that polyurea/Kevlar fabric composites offer better impact resistance than conventional Kevlar fabrics and a 2 mm STF structure could replace approximately 10 layers of Kevlar in a ballistic resistant layer. Our results also showed that a high-strength composite laminate using the best polyurea/Kevlar plates combined with the STF structure was more than 17% lighter and thinner than the conventional Kevlar laminate, indicating that the high-strength protective material developed in this study is superior to the traditional protective materials.

Experimental and numerical investigation of Kevlar and UHMWPE multi-layered armors against ballistic impact

This work aims to prepare hybrid composites to evaluate their behavior under ballistic impact experimentally and numerically. Multilayered armors were designed as ceramic/woven fabric reinforced with epoxy/5074 Al-alloy. Silicon carbide (SiC) represents the first layer against the bullet. Aramid fabric (Kevlar) reinforced epoxy (KEV/EPX), or Ultra-high molecular weight polyethylene (UHMWPE) reinforced epoxy (UPE/EPX) represent the intermediate composites, whereas, the back layer was 5074 Al-alloy. In experimental ballistic tests, a 9 mm Full Metal Jacket FMJ bullet was launched at 307 m/s towards armor 30*30 cm2. The Finite Element Method (FEM) is used to simulate the ballistic impact resistance of armor. Results from simulation and experimental testing were compared with ballistic tests and there was a good agreement. The result shows that a SiC+UPE/EPX+Al-alloy and a SiC+KEV/EPX+Al-alloy were able to stop the 9 mm FMJ bullet, and showed that the bullet perforated many layers of armor without penetration. The backface signature (BFS) was also measured. It is within the permissible range. SiC+UPE/EPX+Al-alloy absorbed more energy compared to SiC + KEV/EPX + Al-alloy. The SiC+UPE/EPX+Al-alloy, the ceramic layer absorbed more energy than the UPE/EPX and Al-alloy, reaching 80.5% of the total energy, while in the SiC+KEV/EPX+Al-alloy, the ceramic layer absorbed more energy than the KEV/EPX and Al-alloy, reaching 78.4% of the total energy. UPE/EPX absorbed energy more than KEV/EPX. That reached 19% of the total energy, while KEV/EPX absorbed about 15% of the total energy. The aim of using ansys Autodyn and explicit dynamic is to calculate the amount of kinetic and absorbed energies and to compare the deformation amount with experimental results.

Energy Absorption and Limit Velocity of Epoxy Composites Incorporated with Fique Fabric as Ballistic Armor-A Brief Report.

Polymer composites reinforced with natural fabric have recently been investigated as possible ballistic armor for personal protection against different levels of ammunition. In particular, fabric made of fique fibers, which is extracted from the leaves of the Furcraea andina, was applied as reinforcement for polymer composites used in a multilayered armor system (MAS). The superior performance of the fique fabric composites as a second MAS layer motivated this brief report on the determination of the absorbed energy and capability to limit velocity in the stand-alone ballistic tests. The single plates of epoxy composites, which were reinforced with up to 50 vol% of fique fabric, were ballistic tested as targets against 7.62 mm high-speed, ~840 m/s, impact ammunition for the first time. The results were statistically analyzed by the Weibull method and ANOVA. The absorbed energies of the 200–219 J and limit velocities of 202–211 m/s were found statistically similar to the epoxy composites reinforced with the fique fabric from 15 to 50 vol%. Predominantly, these findings are better than those reported for the plain epoxy and aramid fabric (KevlarTM) used as stand-alone plates with the same thickness. Macrocracks in the 15 and 30 vol% fique fabric composites compromise their application as armor plates. The delamination rupture mechanism was revealed by scanning electron microscopy. By contrast, the integrity was maintained in the 40 and 50 vol% composites, ensuring superior ballistic protection compared to the use of KevlarTM.

Influence of Rigid Brazilian Natural Fiber Arrangements in Polymer Composites: Energy Absorption and Ballistic Efficiency

Since the mid-2000s, several studies were carried out regarding the development of ballistic resistant materials based on polymeric matrix composites reinforced with natural lignocellulosic fibers (NLFs). The results reported so far are promising and are often comparable to commonly used materials such as KevlarTM, especially when used as an intermediate layer in a multilayer armor system (MAS). However, the most suitable configuration for these polymer composites reinforced with NLFs when subjected to high strain rates still lacks investigation. This work aimed to evaluate four possible arrangements for epoxy matrix composite reinforced with a stiff Brazilian NLF, piassava fiber, regarding energy absorption, and ballistic efficiency. Performance was evaluated against the ballistic impact of high-energy 7.62 mm ammunition. Obtained results were statistically validated by means of analysis of variance (ANOVA) and Tukey’s honest test. Furthermore, the micromechanics associated with the failure of these composites were determined. Energy absorption of the same magnitude as KevlarTM and indentation depth below the limit predicted by NIJ standard were obtained for all conditions.

Ballistic Efficiency of Multilayered Armor System Reinforced with Jute-Kevlar Epoxy Composite against High-Energy Steel Core Projectile

Ballistic Efficiency of Multilayered Armor System Reinforced with Jute-Kevlar Epoxy Composite against High-Energy Steel Core Projectile

Hypersonic impact properties of pristine and hybrid single and multi-layer C3N and BC3 nanosheets

Carbon, nitrogen, and boron nanostructures are promising ballistic protection materials due to their low density and excellent mechanical properties. In this study, the ballistic properties of C3N and BC3 nanosheets against hypersonic bullets with Mach numbers greater than 6 were studied. The critical perforation conditions, and thus, the intrinsic impact strength of these 2D materials were determined by simulating ballistic curves of C3N and BC3 monolayers. Furthermore, the energy absorption scaling law with different numbers of layers and interlayer spacing was investigated, for homogeneous or hybrid configurations (alternated stacking of C3N and the BC3). Besides, we created a hybrid sheet using van der Waals bonds between two adjacent sheets based on the hypervelocity impacts of fullerene (C60) molecules utilizing molecular dynamics simulation. As a result, since the higher bond energy between N–C compared to B-C, it was shown that C3N nanosheets have higher absorption energy than BC3. In contrast, in lower impact speeds and before penetration, single-layer sheets exhibited almost similar behavior. Our findings also reveal that in hybrid structures, the C3N layers will improve the ballistic properties of BC3. The energy absorption values with a variable number of layers and variable interlayer distance (X = 3.4 Å and 4X = 13.6 Å) are investigated, for homogeneous or hybrid configurations. These results provide a fundamental understanding of ultra-light multilayered armors' design using nanocomposites based on advanced 2D materials. The results can also be used to select and make 2D membranes and allotropes for DNA sequencing and filtration.

Ballistic Performance of Guaruman Fiber Composites in Multilayered Armor System and as Single Target.

Multilayered armor systems (MAS) with a front ceramic layer backed by a relatively unknown Amazonian guaruman fiber-reinforced (Ischnosiphon koem) epoxy composites, as second layer, were for the first time ballistic tested against the threat of 7.62 mm rifle ammunition. The amount of 30 vol% guaruman fibers was investigated in three distinct configurations: (i) continuous aligned, (ii) 0–90° cross-laid, and (iii) short-cut randomly dispersed. Additionally, single-target ballistic tests were also carried out in the best MAS-performed composite with cross-laid guaruman fibers against .22 caliber ammunition. The results disclosed that all composites as MAS second layer attended the US NIJ standard with corresponding penetration depth of (i) 32.9, (ii) 27.5, and (iii) 29.6 mm smaller than the lethal limit of 44 mm in a clay witness simulating a personal body. However, the continuous aligned guaruman fiber composite lost structural integrity by delamination after the 7.62 projectile impact. By contrast, the composite with cross-laid guaruman fibers kept its integrity for subsequent shootings as recommended by the standard. The single-target tests indicated a relatively higher limit velocity for .22 caliber projectile perforation, 255 m/s, and absorbed energy of 106 J for the cross-laid guaruman fibers, which are superior to corresponding results for other less known natural fiber epoxy composites.

Experimental and numerical investigation of hybrid armor against a ballistic impact

PurposeThe main challenge in preparing body armor is achieving a high protection level by using lightweight materials with minimum cost.Design/methodology/approachIn this study, a three-hybrid multilayered armor system is prepared for protection against a ballistic impact wave. These armor systems consist of glass or ceramic tile as a front layer followed by three intermediate layers made of woven fiber reinforced polymer composites and a back layer made of either aluminum or polypropylene.FindingsAll armor systems were successful in impeding the projectile from perforating, that is materials selection played an important role in stopping the ballistic impact wave. Almost an identical ballistic behavior was recorded between the experimental and numerical simulation by using ANSYS AUTODYN which means that the simulation could be used in advance to reduce the time required for practical experiments and the cost of using materials in experimental tests will be lessened. The effect of projectile geometry also had been studied, and it showed a noticeable role in changing ballistic behavior.Originality/valueThe originality of this research is in using carbon and glass fiber which are woven together in addition to adding polypropylene layers in armor preparation.

A numerical study on the influence of hole defects on impact behavior of Twaron®fabric subjected to low-velocity impacts

In the present study, a finite element impact model was created and analyzed by commercial FEM code ANSYS®-AUTODYN and then validated by drop weight impact experiment. Moreover, models of single- and multilayer panels of plain weave as well as different weaving architectures were designed and created with and without holes to compare impact properties. The influence of the size and location of hole defect on the impact behavior of single-layer Twaron®fabric were investigated, the degree of influence of hole defects with different sizes on the impact behavior and the influence level by different location of the hole defects were well investigated in. In addition, the effect of hole defects on the impact behavior of multi-layer armor panel were studied. Hole defects were less influential in terms of impact contact force and had less severe constraining effect on front layer of the panel when the number of multi-layer armor panels increased. Furthermore, the effect of hole defects on the impact behavior of different weaving architectures (i.e. plain, twill, basket, and satin weave) were analyzed. Plain weave fabric had the highest energy absorption capability in impact scenarios with and without holes among all the woven architectures. Plain weave fabric was the most affected and twill weave was the least affected by hole defects in terms of transverse wave velocity; the satin weave was the most affected and the twill weave was the least affected by hole defects in terms of energy absorption. These findings will provide guidance for engineering of soft body amour and composite materials.

ROUGHNESS FACTOR FOR MULTI-LAYER ARMOUR AS OVERTOPPING ESTIMATOR

Nowadays one of the most challenging problem for engineers is to adapt existing coastal structures to climate changes. Wave overtopping is highly sensitive to the increasing extreme water depths due to higher storm surges coupled with sea level rise. One way to face these problems for rubble mound breakwaters is to add one or more layers to the existing armour. Prediction of wave overtopping of coastal structures is presently obtained from empirical formulae in EurOtop (2018). For the case of overtopping over multi-layer armour, no validated method exists, so prediction must be based upon assumptions and judgement, with related uncertainties. This study is focused on the effects of different types of armour, the number of layer and other structural characteristics on the roughness factor f. The main effects of porosity and roughness will be investigated. This paper analyzes the results of several new physical model tests of different rubble mound breakwaters reproduced at the new medium scale random wave flume of the Department of Engineering of Roma Tre University.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/8cOdqkqQ-9s

COMBINED METHOD OF MANUFACTURING ARMORED STEEL

Foreign and domestic experience has shown the prospects of using heterogeneous multilayer armor instead of homogeneous. Studies have shown that the method of explosion welding for low-plastic and high-strength steels has limitations on the thickness of the thrown plate of 10-12 mm, which allows us to recommend it for the production of multilayer composite armor. The combined technology (explosion welding + hot batch rolling) provides a three-layer armor plate with an intermediate layer of plastic steel with high strength properties and a defect-free joint structure. The introduction of layers of plastic metals into the composition of multi-layer armor makes it possible to increase the armor resistance. The combined technology can be recommended for the production of wear-resistant and armored bimetal.

Glass fabric reinforced polybenzoxazine composites filled with nanosilica: A High impact response poises use as strike panels in multilayered armor applications

Glass fabric reinforced polybenzoxazine-based composites filled with nanosilica (nano-SiO2) particles were used to create strike panels for multilayered armor applications. The effect of the added nano-SiO2 on the mechanical properties and ballistic impact responses of the composites was quantified using a variety of techniques and related to the interfacial interactions between the two materials. Impact response was effectively mitigated by the added nano-SiO2 as composite panels which contained the additive exhibited smaller damage areas as well as lower penetration depths after being subjected to 5.56 × 45 mm projectiles when compared to composite panels that lacked the additive. Furthermore, a series of numerical simulations predicted that composites of appropriate thickness should protect against the penetration of projectiles with velocities of 930 ± 20 m/s and ballistic limit velocities as high as 1075 m/s. Collectively, these results indicate that the composites may be used as strike panels in ballistic armor applications.

ИССЛЕДОВАНИЕ ПРОЧНОСТИ ПРОЗРАЧНОЙ БРОНИ НА ВЫСОКОСКОРОСТНОЙ УДАР ЦИЛИНДРИЧЕСКИМ УДАРНИКОМ МЕТОДОМ КОМПЬЮТЕРНОГО МОДЕЛИРОВАНИЯ

When manufacturing transparent multilayer armor of high threat level, the reinforced silicate glass and transparent ceramics with protecting back films are usually used. The hardness of the front layer of the shield should be much higher than that of the impactor. A promising option is the use of a single leucosapphire crystal. However, due to its high cost and the impossibility of providing large-sized samples, the transparent polycrystalline materials are developed. One of the most advanced materials is ALON, which is close to leucosapphire in strength characteristics. The aim of this work is to develop a mathematical model to calculate the impact interaction of fragmentation elements with transparent armor. The numerical study is carried out using proprietary software systems. Calculations of the high-speed impact of the steel cylindrical impactor are implemented for three types of shields made of transparent armor. The first two-layer target is made of 20 mm thick tempered glass and a 4 mm thick polycarbonate layer. The second and third targets are three-layered. The front layer of the second target is made of ALON, and the spinel is used for the third one. The second and third layers in these targets are made of tempered glass and polycarbonate, respectively. The calculated results show that ALON is the most impact-resistant material, while spinel is a little less resistant.

Comparative mechanical properties between biocomposites of Epoxy and polyester matrices reinforced by hemp fiber

Natural fibers have, in past decades, been increasingly used as reinforcement of polymer matrix composites in substitution for synthetic fibers. This work presents a comparative study on the mechanical properties of both epoxy and polyester composites reinforced with promising hemp fiber. The comparison would allow which of these thermoset matrices is more adequate for novel biocomposites to be used in technological applications. Amounts of 10, 20 and 30vol% of continuous and aligned hemp fibers were mixed with either epoxy or polyester inside steel molds kept under pressure and cured for 24h at room temperature. Plain epoxy and polyester plates were also fabricated for control samples. Basic characterization by Fourier transform infrared spectroscopy was preliminarly performed. Mechanical properties were obtained in flexural and tensile tests according to ASTM standards. Results were statistically compared by ANOVA and Tukey tests. Fracture was analyzed by scanning electron microscopy. For higher amount, 30vol% of reinforcing hemp fiber, the epoxy composites disclosed superior strength than those of polyester composites. Indeed, for epoxy composites the flexural and tensile strength, 76.7 and 50.5MPa, respectively, are higher than corresponding 49.1 and 25.4MPa, respectively, for polyester composites. As for the elastic modulus, the flexural of 30vol% hemp fiber/epoxy composites, 3.8GPa, was superior to 30vol% hemp fiber/polyester, with 1.2GPa. These results indicate a potential application of hemp fiber/epoxy composites as part of multilayered armor systems for personal ballistic protection.

Ballistic performance and statistical evaluation of multilayered armor with epoxy-fique fabric composites using the Weibull analysis

The ballistic performance of multilayered armor system (MAS) with front ceramic tile, followed by a laminate of up to 50vol.% of fique fabric-reinforced epoxy matrix and back by a 5062H34 aluminum alloy was evaluated. The backface signature (BFS) caused by the bullet in a block of clay witness behind the target was used to evaluate the MAS ballistic performance according to international standards. The results using high-velocity 7.62mm ammunition show a BFS similar to a MAS second layers of Kevlar™ laminate with the same thickness. The Weibull analysis statistically provides the reliability of BFS test results. Fracture examinations by scanning electron microscopy (SEM) revealed that the epoxy-fique fabric composite has different types of energy dissipation mechanisms. These are the same capture of ceramic fragments by a mechanic of incrustation presented in Kevlar™ laminate. Among the tested materials, the 40vol.% fabric composite was found to be a better alternative to replace Kevlar™. The lower cost of the epoxy-fique fabric composite is an additional advantage that favors its substitution for the aramid fabric.

Calculation of armor-resistant metal multilayer armored structures using the finite element method

At present, when the power of modern kinetic weapons is constantly increasing, traditional metallurgical and materials science approaches to the production of homogeneous rolled steel of armored steels are no longer able to provide high dynamic stability. Fulfillment of this requirement leads to a significant increase in the thickness of the armor and, accordingly, the mass of the armored structure as a whole. One of the ways to solve this problem is the use of multilayer metal composites. The combination of high hard (but brittle) and soft (but viscous) steel layers into composites provides composites with a combination of hardness and viscosity that cannot be achieved using traditional methods of manufacturing armored steels (an emergenton property).In this paper, the process of interaction of high-speed impactor with protective multilayered armored obstacles, which was created by welding solid layer composites in a solid phase (without melting) by vacuum-deformation technique is considered.The mechanism of the use of the finite element method for calculating the protective strength of the protective obstacles is investigated. Selected and substantiated source data for simulation modeling. For the modeling of physical phenomena that occur in the impactor and obstacle, such as strain and speed hardening, temperature weakening, destruction, etc. models of behavior of materials were used, which in the general case consist of three main elements: the state of equation, plasticity model and the damage model.The results of calculating the armored-strength resistance of a two-layer armor plate of the following structure: the first layer (frontal) - instrumental carbon steel HRC >= 60 thickness 6 mm, second (back) - steel HRC=40 thickness 4 mm with the impact of impact high-impact impressive element. Influence of the features of the technology of compound of layers on the behavior of the center of mass velocity and the bottom of bullet velocity of and the distribution of the equivalent stress across the Mises is considered. Further researches are related to obtaining the dependence of armor-resistant multilayer armor plates on their overall thickness and structure (composition and ratio of layers), which will allow formulating recommendations for the choice of protective structures.

Effect of Graphene Oxide Coating on Natural Fiber Composite for Multilayered Ballistic Armor.

Composites with sustainable natural fibers are currently experiencing remarkably diversified applications, including in engineering industries, owing to their lower cost and density as well as ease in processing. Among the natural fibers, the fiber extracted from the leaves of the Amazonian curaua plant (Ananas erectifolius) is a promising strong candidate to replace synthetic fibers, such as aramid (Kevlar™), in multilayered armor system (MAS) intended for ballistic protection against level III high velocity ammunition. Another remarkable material, the graphene oxide is attracting considerable attention for its properties, especially as coating to improve the interfacial adhesion in polymer composites. Thus, the present work investigates the performance of graphene oxide coated curaua fiber (GOCF) reinforced epoxy composite, as a front ceramic MAS second layer in ballistic test against level III 7.62 mm ammunition. Not only GOCF composite with 30 vol% fibers attended the standard ballistic requirement with 27.4 ± 0.3 mm of indentation comparable performance to Kevlar™ 24 ± 7 mm with same thickness, but also remained intact, which was not the case of non-coated curaua fiber similar composite. Mechanisms of ceramic fragments capture, curaua fibrils separation, curaua fiber pullout, composite delamination, curaua fiber braking, and epoxy matrix rupture were for the first time discussed as a favorable combination in a MAS second layer to effectively dissipate the projectile impact energy.

Ballistic performance of multilayered armor with intermediate polyester composite reinforced with fique natural fabric and fibers

Multilayered Armor Systems (MASs) with a front ceramic followed by synthetic fabric are currently used against high velocity ammunition. In these armors, the front layer, which shatters the ceramic and spalls the bullet, is followed by an intermediate layer, usually plies of synthetic aramid fabric (Kevlar®). In the present work, the intermediate Kevlar® layer was replaced by an equal thickness layer of two configuration of fique fibers, as fabric or aligned fibers. Both fique fabric and aligned fibers in amounts of 10, 20 and 30vol% were used to reinforced polyester matrix composite. Ballistic impact tests against high velocity 7.62 caliber ammunition revealed that the plain polyester as well as the fique fabric and aligned fiber composites have a relatively similar shock impedance performance as that of the Kevlar®. Indentation around 16–20mm in witness clay for MASs with fique fabric and aligned fique fiber polyester composites as second layer, were better than that of 23mm for Kevlar®. These values attended the US National Institute Justice standard, which requires a maximum of 44mm for body protection. The energy dissipation mechanisms related to the contribution of fique fabric and fibers composites were analyzed in terms of distinct failure modes, visually supported by scanning electron microscopy. These were found to be the same mechanisms recently disclosed for aramid fabric and other natural fibers composites.