Multilayered Armor Research Articles

An optimization scheme for a multilayer armour module against 7.62 mm armour piercing projectile

This study presents a methodology to find the optimal sequence and thicknesses of individual material layers in a multilayer armour module. The methodology is demonstrated with application to three different metal alloys: Armox-500T, Ti-6Al-4V and Al-2024. Numerical simulations are performed first to study the ballistic impact behaviour of these three materials using AUTODYN-3D code. The results of numerical simulations are compared with experimental results for validating the numerical models. Thereafter, a three-layer armour module consisting of these three materials is optimized to defeat 7.62 armour piercing projectile with minimum weight. The optimization process involves carrying a set of numerical simulations based on the design of experiment approach to generate a response surface for the ballistic performance of a composite module. A new ballistic performance parameter is introduced to measure the ballistic response of the module by combining depth of penetration and residual velocity of the projectile to bring uniformity between two cases of partial and complete penetration. The proposed parameter provides more information on ballistic performance. The response surface for ballistic performance parameter is generated in terms of thicknesses for six possible combinations of three material layers. The adequacy of the proposed optimization scheme is confirmed with ballistic experiments. The sequence Armox-500T/Ti-6Al-4V/Al-2024 with thicknesses 5.5, 8.5 and 13 mm, respectively, is found to be the best against 7.62 mm armour piercing projectile. Furthermore, the performance of each individual material is compared with an optimized three-layer armour module. The composite module is found to be weight efficient over Armox-500T, Al-2024 and provides better thickness efficiency over Al-2024. The weight efficiency and thickness efficiency of Ti-6Al-4V are found to be comparable to the composite module. This study emphasizes the necessity of developing new procedures to provide reliable estimates of design parameters for a multilayer armour module.

Upon Using of Plastics Layer in Light Multilayered Armor

The concept of ballistic protection is a subject of great importance and is defined as representing all the capabilities of the military vehicle to withstand attacks, in order to ensure protection of the crew during the missions. The projectile-plate impact research must answer a series of questions on designer or fighter behalf, among which the most important would be whether the bullet penetrates or perforates and whether the velocity after the perforation ensures a lethal effect on the personnel. The current paper presents the numerical evaluation of the working together of aluminum layers with plastic materials in a multilayer structure with honeycomb core, on impact with a rigid projectile. Plastic materials have revolutionized many industries and they are increasingly used due to their main properties, low mass and high strength. The research included the use of plastics, the positioning within the panel and the study of the two constructive versions of the structure, with coupled and uncoupled layers. Post-processing model and interpretation of the results are offered and these could be enriched and customized for other situations, similar or less similar, implicitly, the method is provided, finding a quick answer to certain questions.

Guaruman: a Natural Amazonian Fiber with Potential for Polymer Composite Reinforcement

The Amazonian region of South America is known for its diversified number of plants from which food, medicine, wood and fibers have, since long time, been produced by local natives. A typical example is the guarumã (“guaruman”as suggested English spelling) scientifically identified as Ischinosiphon koem, an abundant plant found in the low lands alongside rivers of the state of Para in Brazil. Fibers extracted from the stem of the guaruman are used in ropes and baskets owing to their strength. In the present work, the possibility of applying guaruman fibers as reinforcement of polymer matrix composites is, for the first time, investigated. Amounts up to 30 vol% of continuous and aligned fibers were incorporates into epoxy matrix composites. Density measurements disclosed the guaruman to be one of the lightest natural fibers. Tensile tests indicate that the guaruman fiber addition was able to improve the composite elastic modulus. However, no significant change was found in the ultimate strength, total strain and resilience. On the other hand, a cost-effective analysis revealed a substantial reduction of ~29% in the epoxy composite price due to the incorporation of fibers. Preliminary ballistic evaluation disclosed a potential for application of guaruman epoxy composites in multilayered armor.

Evaluation of the Projectile's loss of Energy in Polyester Composite Reinforced with Fique Fiber and Fabric

Firearms threat has always been a matter of personal concern, especially to soldiers in armed conflicts as well as police officers and civilians involved with public security. A multilayered armor system (MAS) is intended to personal protection against high kinetic energy ammunition, such as that used in rifles. MAS layers are normally composed of a front ceramic followed by a layer that must show both high impact resistance and low weight. Usually, synthetic fiber fabrics, such as aramid in Kevlar® and ultra-high molecular weight polyethylene (UHMWP) in Dyneema® are commonly used as the second layer. Currently, composites reinforced with natural fibers are also being considered as second MAS layer due to their good performance associated with the advantages of being cheaper and environmentally friendly. The fique is a relatively unknown natural fiber extracted from leaves of a plant native of South American Andes. In the present work, fique fibers and fique fabrics incorporated in polyester composite plates with volume fraction of 10, 20 and 30% were ballistic tested. The calculated projectile loss of energy indicated a relatively large energy dissipation by the composite. The tested specimens were statistically treated by the Weibull analysis and were examined by scanning electron microscopy.

Thickness assessment and statistical optimization of a 3-layered armor system with ceramic front and curaua fabric composite/aluminum alloy backing

The curaua fiber is one of the strongest natural lignocellulosic fibers and its non-woven fabric has potential for engineering applications. Recent investigation on multilayered armor systems (MAS) using natural fiber and fabric composites has shown promising results. In the present work, a MAS with front alumina ceramic followed by a curaua fabric-reinforced composite and backed by an Al alloy is investigated for the influence of the thickness/areal density of layers in the ballistic behavior of the armor. For the first time, an optimized thickness ratio for the layers is proposed. The Box-Behnken Design (BBD) and Multiple Regression Analysis (MRA) are applied to study the MAS properties and to improve the armors performance. Standard ballistic tests are performed, and the back-face signature (indentation in clay witness also known as trauma) is used as a measure of the MAS performance. The results reveal which is the most trauma absorptive layer, while the fracture mechanisms indicate the synergy between the layers. An optimized thickness ratio showed 56% reduction in the armor thickness compared to a fully aramid laminate armor as well as 8.8% reduction compared to the previous studied thickness ratio.

Piassava Fiber as an Epoxy Matrix Composite Reinforcement for Ballistic Armor Applications

The ballistic performance of piassava fiber-reinforced epoxy matrix composites was evaluated as an intermediate layer in multilayered armor systems (MASs). The composites were produced varying the volumetric fractions of piassava fibers, in a range of 10–50 vol.%, embedded in DGEBA/TETA as the epoxy matrix. These composites were adhesive bonded to a MAS composed of a frontal Al2O3 ceramic tile and an aluminum sheet alloy as the third layer. Ballistic tests were conducted using 7.62-mm-high velocity ammunition. The evaluation of the ballistic performance of the system was measured by the depth of penetration caused in a clay witness, which simulates the consistency of the human body, in accordance to some requirements of the NIJ standard 0101.06. The fractured materials were analyzed after the ballistic tests by scanning electron microscopy. The ballistic results showed that MASs using piassava fiber composites as a second layer are within the depth of penetration bounds to be considered as an efficient protection. This indicates that piassava fiber, a green material, is a promising material to be used in composites for ballistic armor applications.

Ballistic comparison between epoxy-ramie and epoxy-aramid composites in Multilayered Armor Systems

The ballistic protection against high-energy projectiles, such as the 7.62mm, is more efficiently performed by means of multilayered armor systems (MAS). A MAS might be composed of a ceramic front, followed by a fiber/fabric composite as intermediate layer, and a ductile metal back layer. In a previous investigation, a MAS with intermediate layer of epoxy composite reinforced with 30vol.% of ramie fabric was ballistic tested against 7.62mm ammunition and compared to MAS with Kevlar® (aramid fabric laminate) as intermediate layer. Both MAS met the standard requirements, but a significant cost reduction favored the ramie fabric composite. In the present work, two other related epoxy composites, one reinforced with raw ramie fibers and other with aramid fabric layers, are investigated as MAS intermediate layer. The objective is to achieve similar ballistic performance with more economical and/or environmentally friendly materials. The results indicate that both new composites met the requirements with comparable ballistic performance as the previously investigated ramie fabric and Kevlar®. Moreover, the ramie fiber composite MAS was the least expensive, among all of them, being 14% cheaper than the previously studied ramie fabric composite MAS.

Microstructural Evaluation of a 5052 H34 Aluminum Alloy Used in Multilayered Armor

Among the aluminum alloys, the 5052 has been extensively investigated aiming at high rate deformation applications, owing to its high mechanical strength, plasticity and toughness. In this work, the microstructure and microhardness of a 5052 H34 alloy were investigated. This alloy was subjected to ballistic impact with 7.62 mm ammunition as back layer of a multilayered armor system composed of a ceramic and a composite material. An increase in the microhardness was observed. However, changes in the microstructure were not significant. The fracture aspect of the alloy in the high deformation rate was compared to that of a tensile tested sample. A stronger plastic behavior was verified in ballistic tested samples.

Performance of jute non-woven mat reinforced polyester matrix composite in multilayered armor

This paper presents results obtained through ballistic tests on multilayered armor system (MAS) using polyester composite reinforced with jute non-woven mat as second layer. Following international standard tests are carried out with ammunition 7.62×51mm, with a velocity above of 800m/s. The MAS is composed of a front layer with hexagonal ceramic tile (alumina doped with 4wt% of niobia), the second layer of polyester matrix composite reinforced with 30vol% of jute non-woven mat and the third layer an aluminum alloy plate. The utilization of polymeric composites reinforced with natural fibers to replace the aramid fabric (Kevlar™) is of interest because their performances are similar in the armor system but the composite is less expensive. Scanning electron microscopy analyses show that the polyester/jute non-woven mat composite captured ceramic fragments through mechanic incrustation. Moreover the replacement of aramid fabric for polyester matrix composites reinforced with jute non-woven mat provides weight reduction of the MAS by 5.4% and a cost reduction of 474%.

Effect of the impact geometry in the ballistic trauma absorption of a ceramic multilayered armor system

Ceramic armors are frequently used for protection against high energy projectiles, such as the 7.62mm and 5.56mm. Recently, it has been demonstrated that a modification in the geometry of the impact face, from flat to convex, enlarges the stress distribution zone created by the projectile-target interaction. This effect raises the projectile's energy absorption and might improve the user's safety. In the present work, the objective is to characterize ceramic armor plates with convex impact face, by means of the NIJ-0101.06 (2008) standard methodology, aiming to provide an eventual application in armor vests. The characterization is based on the measurement of the backface signature, a deformation behind armor imprinted in a reference material that simulates the consistency of the human body. The results showed significant improvement in the ballistic performance after the impact geometry modification.

A review of recent research on materials used in polymer–matrix composites for body armor application

The development of personal protection systems with improved ballistic performance and reduced weight has received a great interest in the last decade with the unfortunate ever-increasing threats and conflicts. In this review, the ordinarily polymeric fibers used in body armors manufacturing were first reported, then some nanomaterials, such as carbon nanotubes and graphene with advanced structural and mechanical properties, as well as their potential reinforcement of armor composites were investigated through some recent studies available in the literature. Additionally, natural fibers integrated into multilayered armor systems, and ballistic tests which endorse their future importance were also cited. This short review which sheds light on novel materials used in personal armor systems, a specific and an important topic that was not previously reviewed, aims to provide to the new researchers, engineers and manufactures in this field some guidelines about what are the promising materials that can be used in order to construct the ultimate body armors of the future.

Fique Fabric: A Promising Reinforcement for Polymer Composites.

A relatively unknown natural fiber extracted from the leaves of the fique plant, native of the South American Andes, has recently shown potential as reinforcement of polymer composites for engineering applications. Preliminary investigations indicated a promising substitute for synthetic fibers, competing with other well-known natural fibers. The fabric made from fique fibers have not yet been investigated as possible composite reinforcement. Therefore, in the present work a more thorough characterization of fique fabric as a reinforcement of composites with a polyester matrix was performed. Thermal mechanical properties of fique fabric composites were determined by dynamic mechanical analysis (DMA). The ballistic performance of plain woven fique fabric-reinforced polyester matrix composites was investigated as a second layer in a multilayered armor system (MAS). The results revealed a sensible improvement in thermal dynamic mechanical behavior. Both viscoelastic stiffness and glass transition temperature were increased with the amount of incorporated fique fabric. In terms of ballistic results, the fique fabric composites present a performance similar to that of the much stronger KevlarTM as an MAS second layer with the same thickness. A cost analysis indicated that armor vests with fique fabric composites as an MAS second layer would be 13 times less expensive than a similar creation made with Kevlar™.

Performance of Plain Woven Jute Fabric-Reinforced Polyester Matrix Composite in Multilayered Ballistic System.

The ballistic performance of plain woven jute fabric-reinforced polyester matrix composites was investigated as the second layer in a multilayered armor system (MAS). Volume fractions of jute fabric, up to 30 vol %, were mixed with orthophthalic polyester to fabricate laminate composites. Ballistic tests were conducted using high velocity 7.62 mm ammunition. The depth of penetration caused by the bullet in a block of clay witness, simulating a human body, was used to evaluate the MAS ballistic performance according to the international standard. The fractured materials after tests were analyzed by scanning electron microscopy (SEM). The results indicated that jute fabric composites present a performance similar to that of the much stronger Kevlar™, which is an aramid fabric laminate, as MAS second layer with the same thickness. The mechanism of this similar ballistic behavior as well as the comparative advantages of the jute fabric composites over the Kevlar™ are discussed.

The Effect of Thickness on Aramid Fabric Laminates Subjected to 7.62 MM Ammunition Ballistic Impact

Due to increasing improvement of weaponry and ammunition, attention is being given to the development of new materials that could more effectively resist to ballistic impact. In order to stop high energy bullets, with speed above 800 m/s, a high strength material is necessary. However, if just one material is used, then a relatively thick piece is required, which might affect negatively the wearer mobility. The objective of this work is to investigate the effect of thickness on the ballistic behavior of aramid fabric laminates, Kevlar®, hit by high energy bullet. The purpose is to find the minimum thickness to avoid perforation. Ballistic tests using conventional 7.62 mm ammunition were performed according to standard procedures. The macro and microscopic aspects of the target specimens were evaluated. The results showed a change in the ballistic behavior of the laminates as their thickness increased. It was found that until the laminate was able to capture the bullet, 96 layers (~50 mm) were required. This is significantly higher than the necessary thickness for a multilayered armor to stop the same 7.62 mm bullet.

Ballistic Performance of Mallow and Jute Natural Fabrics Reinforced Epoxy Composites in Multilayered Armor

Natural fiber reinforced polymer composites have recently been investigated as a component of multilayered armor system (MAS). These composites were found to present advantages when replacing conventional high strength synthetic aramid fabric laminate composite (KevlarTM, with same thickness, as MAS second layer. Continuous and loose natural fibers were up to now mostly used to reinforce these ballistic composites. Only two natural fabrics reinforced polymer composite were so far used with same purpose. Therefore, this work investigated the possibility of substituting KevlarTM for three other natural fabrics, based on mallow and jute fibers, as reinforcement of epoxy composites. Fabrics made of either pure mallow, or 70%mallow/30% jute or 50%mallow/50% jute fibers were separately mixed with epoxy to produce laminate composite plates. These plates were set as second layer of Al2O3/Nb2O5 front ceramic MAS, that were ballistic tested against relatively high energy 7.62 mm ammunition. Indentation depth values caused by the bullet penetration in clay witness, simulating human body behind the MAS, were always found to be below the safety standard limit. These indentation values were similar to those obtained in MAS with KevlarTM as second layer. However, significant economical advantages favor the investigated natural fabric composites over the synthetic Kevlar.

Performance of natural curaua fiber-reinforced polyester composites under 7.62 mm bullet impact as a stand-alone ballistic armor

A multilayered armor system (MAS) is intended to personal protection against high kinetic energy ammunition. MAS layers are composed of materials such as a front ceramic and a back composite that must show both high impact resistance and low weight, usually conflicting characteristics. Synthetic fiber fabrics, such as Kevlar™ and Dyneema™, are the favorite materials to back the front ceramic, due to their high strength, high modulus and relatively low weight. Recently, composites reinforced with natural fibers have been considered as MAS second layer owing to their good performance associated with other advantages as being cheaper and environmentally friendly. Among the natural fibers, those extracted from the leaves of the Ananas erectifolius plant, known as curaua, stand out due to its exceptional high strength and high modulus. Thus, the objective of the present work is to evaluate the performance of curaua fiber-reinforced polyester composites subjected to ballistic impact of high energy 7.62mm ammunition. Composites reinforced with 0, 10, 20 and 30vol.% of curaua fibers were produced and stand-alone tested as armor target to evaluate the absorbed energy. Analysis of variance (Anova) and Tukey's honest significant difference test (HSD) made it possible to compare the results to Kevlar™ laminates. Among the tested materials, the 30vol.% fiber composites were found to be the best alternative to Kevlar™.

High energy ballistic and fracture comparison between multilayered armor systems using non-woven curaua fabric composites and aramid laminates

For personal protection against high kinetic energy projectiles, multilayered armor systems (MAS) are usually the best option. They combine synergistically the properties of different materials such as ceramics, composites and metals. In the present work, ballistic tests were performed to evaluate multilayered armor systems (MAS) using curaua non-woven fabric epoxy composites as second layer. A comparison to a MAS using aramid (Kevlar™) fabric laminates was made. The results showed that the curaua non-woven fabric composites are suitable to the high ballistic applications, and are promising substitutes for aramid fabric laminates.

Mallow Fiber-Reinforced Epoxy Composites in Multilayered Armor for Personal Ballistic Protection

Lighter and less expensive polymer composites reinforced with natural fibers have been investigated as possible components of a multilayered armor system (MAS) for personal protection against high-velocity ammunition. Their ballistic performance was consistently found comparable with that of conventional Kevlar® synthetic aramid fiber. Among the numerous existing natural fibers with the potential for reinforcing polymer composites to replace Kevlar® in MAS, mallow fiber has not been fully investigated. Thus, the objective of this work is to evaluate the ballistic performance of epoxy composites reinforced with 30 vol.% of aligned mallow fibers as a second MAS layer backing a front ceramic plate. The results using high-velocity 7.62 ammunition show a similar indentation to a Kevlar® layer with the same thickness. An impedance matching calculation supports the similar ballistic performance of mallow fiber composite and Kevlar®. Reduced MAS costs associated with the mallow fiber composite are practical advantages over Kevlar®.

The Role of Sintered Al<sub>2</sub>O<sub>3</sub>-Nb<sub>2</sub>O<sub>5</sub> Front Plate on the Ballistic Performance of Multilayered Armors

The performance of multilayered armor systems (MAS), composed of a front Al2O3-Nb2O5 ceramic plate followed by either plies of aramid fabric layer or curaua fiber reinforced polyester matrix composite layer and backed by an aluminum alloy sheet, was assessed. Ballistic impact tests were performed with actual 7.62 caliber ammunitions. Indentation in a clay witness, simulating a personal body behind the back layer, attested the efficacy of the MAS as an armor component. The ballistic efficiency of the front ceramic dissipating more than 50% of the bullet impact energy was associated with its capacity of fragmentation. As for the remaining energy, the lighter and cheaper curaua fiber composites were found to present a significant advantage as a possible substitute for the usual aramid fabric intermediate layer in MAS for individual protection against high speed projectiles.

Ballistic Application of Coir Fiber Reinforced Epoxy Composite in Multilayered Armor

Multilayered armor systems (MAS) composed of relatively lighter materials with capacity to provide personal ballistic protection are being extensively investigated and used in armor vests. A typical MAS to stand high impact energy 7.62 mm bullet has a front ceramic followed by an aramid fabric laminate, such as Kevlar™. Since both the army and municipal police personnel might need to wear an armor vest, a large number of vests needs to be supplied. In the case of Kevlar™, one of the most expensive MAS material with an expiration time of 5 years, the possibility of its replacement by an equally ballistic efficient low cost material and more durable could be a relevant economical advantage. Natural fibers composites have recently been investigated as possible alternatives for Kevlar™. In particular, the fiber extracted from the coconut fruit, known as coir fiber, normally disposed as waste, could be a low cost material for this purpose. Therefore, the present work investigated the possibility of using coir fiber mantle, with different volume fraction, reinforcing epoxy composites as MAS second layer. It was found that 30 vol% of coir fiber composite displayed similar ballistic performance as compared to Kevlar™ with substantial economical advantage.