An Add-On Armor Design Against 7.62 mm × 51 Armor-Piercing Tungsten Carbide Core Ammunition for Armored Vehicles and Examination of the Ballistic Performance of the Armor

<div class="htmlview paragraph">Recent developments in design of composite armor for lightweight ground vehicle applications is discussed. Composite integral armor (CIA) is a multi-functional hybrid material system that has been successfully demonstrated in the Composite Armored Vehicle. A typical CIA hull consists of a composite cover layer, a ceramic strike face and a thick-section composite backing plate. CIA provides equivalent ballistic performance at reduced areal-density than monolithic armor. Future combat vehicles will require modular armor upgrades of the CIA hull to increase ballistic protection for specific missions. Finite element (FE) modeling has been performed to understand the through thickness wave propagation and the effect of non-linear material behavior in CIA. Innovative design, fabrication and ballistic performance evaluation of a new generation armor utilizing metal foams have been presented.</div>

Investigations of low-temperature-transformation pathways that exist during tungsten carbide formation revealed the novel formation of ‘inverted’ core-shell nanoparticles comprising a tungsten carbide (WC) core and a tungsten shell assisted by an ‘asymmetric heating’ of a compacted tungsten/carbon monolith. X-ray Diffraction (XRD) characterization of the product revealed that tungsten was present in both elemental and carbide forms. The core-shell morphology of the tungsten carbide particles was deciphered from High Resolution Transmission Electron Microscopy (HRTEM) measurements and results from the thermal decomposition of the initially formed metastable W2C nanoparticles. Simultaneously, a portion of the initially formed metastable W2C nanoparticles in the vicinity of excess carbon became stabilized producing carbonensheathed W2C nanoparticles. These findings open new avenues to access unique core-shell morphologies of refractory carbides and for the ambient stabilization of metastable nanoparticles by means of asymmetric heating of monoliths of selected binary or higher compositions. Furthermore, the obtained core-shell nanoparticles provide a platform to produce other experimentally challenging structures. Keywords: Asymmetric, benzene, carbon, core, core-shell, decomposition, disproportionation, heating, HRTEM, shell, solid-state, thermal, tungsten carbide, tungsten, W2C, WC, XRD.

Ballistic performance of armour ceramics: Influence of design and structure. Part 2

Numerical study on ballistic impact behavior of hybrid composites

This study explores the enhancement of Kevlar fabric’s ballistic performance through impregnation with Shear Thickening Fluid (STF) for potential application in soft body armor. The experimental approach often fails to elucidate mechanical phenomena critical for the development of lightweight and high-strength body armor designs. To address this limitation, the finite element method, specifically using ANSYS/LS-DYNA R.13, was employed for a comprehensive analysis. The simulation aimed to evaluate the impact of STF on Kevlar fabric by assessing projectile velocity, force exerted by the projectile onto the fabric, displacement, stress distribution, and fabric failure mechanisms. Kevlar yarn was modeled as a shell element formed into fabric with a sine wave profile, investigating two types of STF: SiO2-PEG200 (S0) and SiO2-PEG200-B4C (S1), differing in maximum viscosities. The addition of STF resulted in increased coefficients of friction on Kevlar, with the highest values observed for the SiO2-PEG200-B4C impregnated fabric ( =0.87 and =0.82). The incorporation of the second STF type (S1) significantly reduced the projectile’s velocity from an initial 200 m/s to 153.2 m/s upon impact. Additionally, the force on the S1 fabric surged to 121,556 N, a threefold increase compared to neat Kevlar. STF's influence was further evidenced by enhanced fabric displacement and more uniform stress distribution upon ballistic impact. The fabric's thickening upon failure indicated STF's ability to enlarge the deformation area, facilitating uniform distribution of ballistic kinetic energy across the impact zone. Notably, the fabric impregnated with the second type of STF, featuring boron carbide (S1), demonstrated superior ballistic performance. This study concludes that STF-impregnated Kevlar fabric, particularly the SiO2-PEG200-B4C variant, not only surpasses the ballistic performance of neat Kevlar but also meets the criteria for NIJ Level IIIA standards, highlighting its potential as a highly effective material for advanced soft body armor designs.

A ceramic/composite add-on armour system with innovative ceramic geometry (cylindrical) against 14.5 × 114 mm API/B32 projectile was developed and ballistic performance of the armour was investigated both experimentally and numerically. Numerical analysis was used to calculate exit velocities of the projectile after passing through the ceramic/composite layer (before penetrating the Armox 500T which simulates hull structure of an armoured vehicle) and also contributed to the selection of optimum ceramic thickness. The calculated projectile velocity-time curves (from numerical analysis) for three different ceramic thicknesses are given comparatively in the study. The curve characteristics are the same for three different analyses. The duration of the total absorption of the projectile energy is about 0.2 microseconds (ms). There were differences in the transmission of the stress wave and the delamination in the Ultra-High-Molecular-Weight Polyethylene (UHMWPE) layers differed as ceramic thickness increases. The separation between the layers varied with the change in projectile energy. As a result of the ballistic test, the armour prevented 14.5 × 114 mm API/B32 ammunition with desired damage mechanisms. In the x-ray image taken after the shootings, it was seen that the ceramic damage was local which enhanced multi-hit resistance capability and the geometry of the cylindrical alumina played an important role in the localization of the ceramic zone damage during the projectile penetration process. Due to this cylindrical ceramic geometry, the projectile moving on after the moment of impact constantly encounters a curved and new surface, and thus it is deflected and exposed to more wear. The areal density of the armour was also reduced by using the UHMWPE (which is one of the composite material whose fibres have the lowest density and good mechanical properties) composite plate as the backing plate.

In this paper, we report our numerical work on the ballistic penetration of various armor designs by a 20 mm fragment-simulating projectile at a velocity of 1000 m/s. For the design with monolithic metal plate, numerical simulations show that final failure of the plate is tearing of the metallic material. Incorporation of ceramic material (i.e., metal/ceramic armor) changes the final failure mode of the armors to plastic bending and stretching of the backing plate. Two types of metal/ceramic designs are studied. One consists of ceramic layer backed by a metal plate, with or without a front metallic faceplate. The other metal/ceramic design utilizes the honeycomb structure and is made by filling the free space in a honeycomb-core sandwich panel with solid ceramics. The ballistic limits (the minimum mass required to stop the projectile) associated with all the designs are obtained and compared. Finite element calculations show that incorporation of ceramic gives a benefit of mass reduction of 20-30%. While utilizing honeycomb structure slightly improves the ballistic limits (compared with the case of ceramic layer backed by metal plate), it could remarkably reduce the deformation of the backing plate at ballistic limits. It is also found that for all metal/ceramic designs, the front faceplate does not contribute to improve the ballistic performances.

Revolutionizing hardness via nanoparticle flux in welding of high-hardness armor steel

The present research involves studies of the influence of the physico-mechanical properties of the ceramics on the ballistic resistance of the new concept of the hybrid, ceramic–multi-layered UHMWPE composite armour developed using SiC and Al2O3 ceramics differing in thickness. Ballistic verification of new design of the ballistic composite armour was conducted in the scope of the protection against more than one shot (multi-hit) using 7.62 × 39 mm MSC and 5.56 × 45 mm SS109 ammunition. Tests of physico-mechanical properties, covering the determination of density, acoustic impedance, Young’s modulus, hardness, and resistance to brittle fracture, were conducted for the ceramic materials. Obtained results show that the ballistic behaviour of the testing system based on ceramic tiles being made of the same materials (SiC or Al2O3) of the different thicknesses does not directly correlate with the hardness, brittle fracturing, or Young’s modulus of ceramics. For ceramic plates of the same thickness being made of different materials in chemical terms, performed studies have shown that the ballistic resistance of the testing system does not only depend on acoustic impedance of ceramic plates, which should be as similar as possible to the acoustic impedance of the backing material in the ballistic armour, but also the resistance to brittle fracturing K1c is an important parameter of the ceramic plates entering the composition of the armour, and it should be as high as possible. Only the combination of these two properties yields the best ballistic protection of the armour when testing using the multi-hit procedure with the use of 7.62 × 39 mm MSC and 5.56 × 45 mm SS 109 ammunition.

In contrast to making male body armor, manufacturers of body armor encounter problems in design and manufacture of female body armor because of the curvaceous body shape of females. The traditional cut-and-sew method could be used to form the dome shape to accommodate the bust area but it gives rise to weakness at the seams against projectile impact. Fabric folding has been another way to form the domes but it also leads to reduced impact performance and wearing discomfort. In this paper, angle-interlock woven fabrics are proposed as an alternative to the conventional plain woven fabrics in making female body armor due to their advantages in moldability without the need of cutting or folding and ease in manufacture. However, it is vital that the angle-interlock fabrics satisfy the ballistic requirements before being employed for the body armor application. Part Ι of this paper reports on an investigation on the ballistic performance of angle-interlock fabrics. It has been found that the angle-interlock fabric is not less than the conventional fabric constructions used for body armor against ballistic impact. Based on the employment of the angle-interlock fabric, Part ΙΙ presents the mathematical modeling of molding of angle-interlock fabrics to form the front panel of female body armor, which would lead to quick creation of female body armor based on the input of the body and bust sizes.

This article presents the characterization and modeling of the U. S. Army Research Laboratory (ARL) 14.5 mm BS41 projectile for ballistic impact conditions. The ARL BS41 is a complex projectile that includes a steel case, inert filler materials, and an armor piercing tungsten carbide (WC) core. The characterization of the WC core is the focus of this work. The core material is a composite comprised of 93% WC and 6% cobalt (Co) and behaves like a very strong metal with little ductility. An approach is presented that determines Johnson-Cook strength and fracture model constants for the WC core using limited laboratory data along with ballistic impact experiments. Numerous 2D computations are presented (including experimental results) that demonstrate the response of the BS41 and the ability to model its behaviour.

: Tungsten carbide (WC) spheres are used as projectiles to study the ballistic performance of armor materials and systems. In order to properly understand and model the interaction between the projectile and the armor, it is necessary to have properties of both. In this study, the physical and mechanical properties of two commercially available WC spheres (nominally 0.25 inch in diameter) used in some ballistic impact studies were determined. One WC sphere had higher density, elastic properties, and hardness but lower strength and fracture toughness compared to the other sphere, indicating a significant difference in the binder content between the two materials.

Achieving lightweight and high-performance bulletproof vests is essential for military and law enforcement, where balancing mobility and ballistic resistance is critical. This study investigates the ballistic performance of multi-layered Ultra-High Molecular Weight Polyethylene (UHMWPE) vests reinforced with titanium (Ti6Al4V) and polyvinyl chloride (PVC). Two innovative vest configurations were evaluated following National Institute of Justice (NIJ) Standard-0101.04 ballistics tests and simulated using the Finite Element Method (FEM). Experimental findings indicated that while Vest 1 significantly absorbed impact energy, it failed to prevent projectile penetration. In contrast, Vest 2, incorporating additional titanium and polymer layers, effectively mitigated the penetration of 9 mm Full Metal Jacket (FMJ) projectiles while maintaining a safe back-face signature (BFS). The FEM simulation results demonstrated strong agreement with the experimental data, validating the effectiveness of multi-material layering in enhancing ballistic resistance. This research presents a strategic integration of titanium and polymer composites designed to achieve superior ballistic resistance while maintaining lightweight properties. These findings provide valuable insights for developing advanced body armor designs suitable for high-performance military and law enforcement applications.

Reduction of back face signature (BFS) or blunt trauma of soft armour panel (SAP) is one of the major aspects of armour design. This research explores the use of stiff polymeric materials (polycarbonate or PC sheet) to mitigate the BFS of hybrid SAPs. Two sets of SAPs were prepared—the first set comprising of para-aramid based woven fabrics and UD laminates and the second, of ultra-high molecular weight polyethylene (UHMWPE) UD laminates. The areal density of all the panels was within the range of 4.7 ± 0.3 kg m−2. The ballistic performance of SAPs was evaluated in terms of BFS and perforation ratio against a 9 mm × 19 mm lead core bullet fired at 430 m s−1 velocity. The BFS of SAPs reduced when PC sheets were used as backing materials, with a maximum improvement of 27.5% noticed in case of the SAP made from woven para-aramid fabrics. PC sheets were able to replace up to 41% of the high-performance materials thereby reducing the materials cost of armour significantly (38%). The outcome of this research opens up possibilities to replace costly high-performance fabrics with low-cost materials while improving the ballistic performance of SAPs.

Based on an energy conservation model, the strength offered by a number of brittle materials has been calculated from depth-of-penetration (DOP) test results. Each material was completely penetrated by a tungsten carbide cored projectile of known kinetic energy and the residual penetration into a ductile aluminium alloy backing material was measured. The energy transferred to the tile by the projectile has been calculated and has been shown to vary linearly with the tile thickness. From the energy transferred to the armour tile, the mean resisting stress that was offered to the penetrator was calculated and for the materials tested, scaled with the material hardness. This work shows that for DOP testing, where the projectile remains intact, the measured DOP is merely a facet of the ceramic’s hardness and not its true ballistic performance. The possibility of using this method to measure the strength of damaged ceramic is also discussed.