Armor Materials Research Articles

Advanced Body Armor Utilizing Shear Thickening Fluid Based on Nanosized Silica Particles

This study reports the ballistic penetration performance of a composite material composed of woven Kevlar® fabric impregnated with a colloidal shear thickening fluid (STF). STF comprised of Nanosized silica particles suspended in polyethylene glycol. The impregnated Kevlar fabric offers equivalent low velocity ballistic performance, on an areal density basis, to neat Kevlar fabric. Compared to neat Kevlar fabric, however, the STF-impregnated composites require fewer layers of Kevlar, resulting in a more flexible and less bulky body armor material. Possible mechanisms responsible for the enhanced ballistic and stab performance of the STF-Kevlar composite are identified.

Ballistic Resistance of Steel with the Structure of a Natural Ferrite-Martensitic Composite

Introduction. For steel armor materials, it is important to reduce the thickness and, consequently, the metal consumption of the protective structure. The previously developed class of materials with the structure of a natural ferrite-martensite composite (NFMC) has characteristics that favor the inhibition of crack development under impact loads and has prospects as an armor material.Problem Statement. The purpose of this work is to evaluate the possibility of using NFMC materials for armor protection devices based on the results of ballistic resistance tests under a high-power concentrated impact (a projectile flying at a hyper-high speed).Theoretical Part. The study of ballistic resistance was carried out on samples of steel 14G2 processed according to various modes. The samples had the shape of plates and a square grid on the surface. Simulation tests of the impact of heat-strengthened dowels from a powder-actuated tool and firing of military small arms at the testing site from an SVD sniper rifle and an AK-74 assault rifle with machine loading ammunition were carried out. The results of simulation tests showed a clear advantage of steel with the NFMC structure. The comparison of the results of firing with military small arms has showed that the ballistic resistance of steel with the NFMC structure depends on the ratio of the volume fractions of ferrite and martensite, which cause different thicknesses of the ductile and strong components of the composite. The highest resistance was observed for a sample with an NFMC structure processed according to the regime: quenching 730°C and tempering 180°C.Conclusions. Steels treated for the NFMC structure can provide effective protection for military personnel with a lower material consumption of armor protection devices, which is due to a special method of braking destruction during a high-power local impact. Thus, the practical application of the developed class of natural composite materials seems promising for obtaining an armor plate with a thinner thickness, which helps to reduce the weight of combat vehicles, increase their mobility and reduce fuel consumption.

Dynamic response of high-entropy alloys to ballistic impact.

High-entropy alloys (HEAs) are promising to provide effective antiballistic capability because of their superior mechanical properties. However, the twinning-active Cantor alloy is found less ballistic resistant, compared with its Mn-free companion. It is unclear how the HEAs resist ballistic impact and why Mn does not benefit the ballistic resistance. Here, we used molecular dynamics simulations to investigate the ballistic resistances of CrMnFeCoNi and CrFeCoNi and elucidate underlying mechanisms. It is shown that the alloys’ ballistic resistances dominantly benefit from active dislocations generated at higher strain rates. Stronger atomic bonding and higher dislocation densities make the CrFeCoNi easier to be strain hardened with elevated toughness to resist high-speed deformation, while weaker atomic bonding and easier occurrence of dislocation tangling make CrMnFeCoNi less resistant to failure under ballistic impact. This work helps better understand the antiballistic behavior of HEAs and guide the design of armor and energy-absorption materials.

Research on Bending Performance of Three-Dimensional Deep Angle Interlock Kevlar/EP Armor Material.

Three-dimensional (3D) woven composites have attracted much attention in the lightweight research of protective armor due to their high specific strength and good impact resistance. However, there are still many gaps in terms of the performance and influencing factors of three-dimensional deep-angle-interlock (3DDAI) Kevlar/EP armor materials. Therefore, in order to prepare 3DDAI Kevlar/EP armor materials with excellent ballistic resistance and mechanical properties, this paper studies the bending performance of 3DDAI Kevlar/EP armor materials and the influence of the number of stacking layers, resin content, laying method, and weft density. Finally, we compare it with the traditional two-dimensional (2D) plain laminated Kevlar/EP armor material. The results showed that when the 3DDAI Kevlar/EP armor material was subjected to bending load, the upper and bottom layers of the material had a great influence on the initial stiffness and fracture strength of the material, respectively; when the material’s warp and weft density are quite different, the utilization rate of the yarn and the strength of the material are negatively affected; the fracture energy of the 3DDAI Kevlar/EP armor material prepared by the orthogonal laying method was about 20% higher than that of the 3DDAI Kevlar/EP armor material with the unidirectional layering method; and the bending performance of the 3DDAI Kevlar/EP armor material in the weft direction was better than that of the 2D plain laminated Kevlar/EP armor material, with the 3DDAI Kevlar/EP armor material having better delamination resistance. The research results will lay the foundation for structural optimization and engineering applications of such materials.

Energy absorption of densified veneer-aramid hybrid composites subjected to ballistic impact

Densified wood technology improves the wood properties such as strength, surface hardness, dimensional stability, and durability. However, the utilization of laminated veneer as densified wood which is used as an armor material, and its ability to absorb ballistic energy has not been researched. The strengthening of the Teak Platinum veneer, which was densified with a hot press, used pre-treatment methods such as partial delignification and self-assembly of bacteria cellulose using Acetobacter xylinum. This research used hybrid and non-hybrid panels. The hybrid panel used epoxy adhesive to combine the laminated aramid fabric and 2 types of densified veneer laminated. Two types of densified veneers consist of the densified veneer with and without stabilizing resin. A ballistic test was carried out on each sample at a distance of 5 m using 9 mm Luger ammunition according to NIJ 0108.01. The ballistic energy absorption was analyzed based on the difference between the initial velocity and the residual velocity of the projectile. The initial velocity and the residual velocity were measured by the chronograph. This result showed that the performance of the hybrid panels was lower than the non-hybrid panels at the same thickness. However, the hybrid panels using aramid and veneer ratio of 2:1 (by volume) and the configuring of fully aramid fabric on the inside was the best combination with a ballistic energy absorption of 78.64% at 354.70 J.

Dynamic response of YAG polycrystalline and single‐crystal transparent ceramics: Experiments and mesoscopic simulations

AbstractDue to superior mechanical and optical properties, yttrium–aluminum–garnet (YAG) is emerging as a potential transparent armor material. Its dynamic behavior, however, remains largely unexplored. In this work, both impact experiments and mesoscopic simulations have been performed to better understand the dynamic response of YAG polycrystalline and single‐crystal transparent ceramics. Experimental results demonstrate that the two samples have remarkably different dynamic behaviors with the increasing shock pressure, in which the Hugoniot elastic limit basically keeps unchanged (∼14 GPa) in YAG polycrystalline ceramic, whereas it varies from 11 to 31 GPa in YAG single crystals. Moreover, elastic precursor decay is visible only in single‐crystal samples. Mesoscopic simulations with a lattice‐spring model reveal that the difference arises from the distinct fracture mode in the two samples. Less damage and coarser fragmentations in YAG single crystal also suggest a probability of better ballistic resistance as transparent armor materials.

T-REX: Numerical tool for tungsten damage assessment for DEMO

One of the R&D focus in the European fusion energy program is to establish a physical and technological basis for reliable power exhaust during entire operational situations of a DEMOstrational power plant. Following the design adopted for ITER, the baseline Plasma Facing Component for DEMO divertor is made of tungsten as armor material. The tungsten divertor target are the most thermally loaded in-vessel components in fusion reactor. The PFCs lifetime is affected by material degradations under the different loadings including High Heat Flux (HHF) and neutron irradiation. It has been reported a loss of mechanical properties due to softening (restoration/recrystallization). Latest finite element modeling developments allow to estimate component lifetime under HHF loading taking into account the progressive mechanical properties change due to softening. We propose here to take into account the influence of thermal and neutron loadings on the tungsten mechanical properties change for PFC lifetime assessment. For this, up to date mechanical properties of tungsten, softened tungsten, and neutron-irradiated tungsten are used as input data in the tool named T-REX (for Tungsten-Response based on EXperimental data). This tool is implemented as a user subroutine in a finite elements code. The influence of the neutron irradiation is studied as function of the dpa dose, the incident heat flux intensity and the current defined divertor component geometries (ITER and DEMO). With the study performed, it is shown that the geometry may be optimized to reduce the damage induced by plasticity. The numerical results also highlights that the plastic strain increment obtained after each thermal cycle reduces with the dpa dose.

Analisa Karakterisasi Baja Paduan As-Cast-Fe-Cr-Mn-Mo Dengan Komposisi Nikel Terhadap Sifat Mekanik Dan Struktur Mikro Hasil Uji Balistik

Lateritic steel is a low-nickel steel with a nickel content of 1-4.5 percent. Steel with a high nickel percentage has better qualities like high strength, corrosion resistance, and weldability. This material is commonly used in crushers and grinding machines. This material can also be utilized as an armor material. A study was undertaken to investigate the ability of laterite steel to be employed as armor material by characteristic testing (impact test and hardness test) and microstructure (metallography) of laterite steel. ASTM standards must be followed in the preparation of all samples. The impact test was performed on 9 samples from 3 specimens, with each sample being placed on an anvil and pounded with a pendulum that the average values of samples A, B, and D were 11 J, 9 J, and 12 J, respectively. The fractures were granular, indicating that the material is extremely fragile. The hardness test was then performed using the Vickers method with a 5 Kgf load. The polished sample is placed immediately on a vise, and then a diamond-shaped indenter is attached; the hardness test value is determined by the size of the trace of the indenter, with the average values of samples A, B, and D being 292.63 HVN, 310.47 HVN, and 464.87 HVN, respectively. Microstructure measurements revealed that sample A formed ferrite perlite, sample B formed lower bainite, and sample D formed martensite phase.

Pengembangan Baja Paduan Tahan Peluru Melalui Proses Hot-Forging Terhadap Morfologi Dan Sifat Mekanik

Laterite steel is steel that has a nickel content of up to 2%. The nickel content can produce steel with superior properties such as: high strength, corrosion resistance, and good weldability properties. With the superior nature of laterite steel is needed in the main tool of the indonesian national tantara weapon system. To find out the performance of damage to bulletproof materials, then conducted research on this laterite steel as a tough armour material by conducting research in the form of mechanical properties testing (Hardness, and Impact) and microstructures (Metalography). Samples are prepared in accordance with ASTM standardization. Based on the results of the hardness test, the average values of F and T samples were 663.9 HVN and 170.7 HVN. Material F qualifies as a ballistic resistant material (armour) because the hardness obtained in accordance with the classification and can withstand bullet penetration well. Then the impact test obtained the average value of the F and T samples is 9 joules and 148 joules. For F samples, the type of fault is a granular fracture and a T sample of the type of fault is a tenacious fracture. As a result of metallographics, sample F has a corrected phase is upper bainite as a matrix and martensite is generally shaped like a fine needle. Then the T sample has a formed phase is dominated by ferrite with soft and tenacious properties. As well as perlite as a matrix with quite hard and strong properties.

Development of irradiation tolerant tungsten alloys for high temperature nuclear applications

Development of refractory metals for application as plasma-facing armour material remains among priorities of fusion research programmes in Europe, China and Japan. Improving the resistance to high temperature recrystallization, enhancing material strength to sustain thermal fatigue cracking and tolerance to neutron irradiation are the key indicators used for the down selection of materials and manufacturing processes to be applied to deliver engineering materials. In this work we investigate the effect of neutron irradiation on mechanical properties and microstructure of several tungsten grades recently developed. Neutron irradiation campaign is arranged for screening purposes and therefore is limited to the fluence relevant for the ITER plasma facing components. At the same time, the neutron exposure covers a large span of irradiation temperatures from 600 up to 1000 °C. Four different grades are included in the study, namely: fine-grain tungsten strengthened by W-carbide (W–4wt.% W2C), fine-grain tungsten strengthened by Zr carbides (W–0.5% ZrC), W alloyed with 10 at.% chromium and 0.5 at.% yttrium (W–10Cr–0.5Y) and technologically pure W plate manufactured according to the ITER specification by Plansee (Austria). The strengthening by W2C and ZrC particles leads to an enhanced strength, moreover, the W–0.5ZrC material exhibits reduced DBTT (compared to ITER specification grade) and is available in the form of thick plate (i.e. high up-scaling potential). The W–10Cr–0.5Y grade is included as the material offering the self-passivation protection against the high temperature oxidation.

Improving fracture toughness of B4C – SiC composites by TiB2 addition

B4C-SiC composites can be used in many areas due to their superior properties. However, in order to be used as a body armor material in areas requiring high performance, their fracture toughness needs a degree of improvement. In this study, 0–20 wt% TiB2 was added to B4C-SiC samples that were consolidated at 1950 °C by spark plasma sintering method. The contribution of TiB2 to the microstructure, elastic and mechanical properties of B4C-SiC composites were investigated. The highest hardness was measured to be 29.5 GPa with 15 wt%TiB2 addition. The highest fracture toughness was 3.08 MPa.m1/2 found at sample made with 10 wt% TiB2. Addition of 10 wt% TiB2 increased the fracture toughness by 28%, with only a 5% decrease in relative density. In addition, the fracture mode of B4C-SiC-TiB2 composites is intergranular due to the addition of TiB2.

Dynamic Response Behaviours of Al<sub>2</sub>O<sub>3</sub> Ceramics with Different Grain Sizes under SHPB Compression Loading

Alumina is the most promising ceramic armor material and SHPB testing is typically used to investigate dynamic deformation behaviour and ballistic mechanisms. In this research the effect of the incident wave shaping technique on the stress equilibrium state during testing was analysed. The compressive strength of alumina ceramic materials was evaluated under high strain rate compressive loads of 1200-1800/s. The SHPB compression strength was found to increase with decreasing grain size to a maximum of 3.80±0.25 GPa, and the ceramic materials studied exhibited high strain-rate sensitive mechanical properties due to crack tip inertia effects.

Armor Layer Uniformity and Thickness in Stationary Conditions with Steady Uniform Flow

The continuous movement of riverbed particles due to turbulent flow determines the stability of non-cohesive riverbeds and banks during riverbed and bank erosion and sedimentation. This study emulated the stable channel design by deriving the low maintenance cost of the channel through bed protection by an armor layer. The study investigated the effects of shear stress and grain size uniformity to determine the minimum non-cohesive armor layer thickness for the stability of riverbeds under steady uniform flow conditions. Experiments were conducted with four different discharges, five armor material gradations, and five bed-slope variations in a full-scale flume. We observed and recorded the behaviors of the five gradations of armor materials for given discharges and bed slopes. Eighty data points were recorded and analyzed. The hydraulic analysis of the flow along with the soil mechanics analysis of the armor materials was done. The soil mechanic analysis was particularly focused on the uniformity coefficient of the armor layer, Cu, to derive the armor layer equation. However, for the manageability of the study, we set the limit of the Cu between 3.0 and 6.0. From the viewpoint of non-erodibility, a wider Cu value indicated a thinner armor layer. Variables that govern the armor layer thickness and the layer thickness itself were derived and proposed. The variables, namely Cu, shear stress (t0 and tc), and mean diameter of the bed load and armor materials (Db50 and Da50). Our results show that these variables governed the thickness of the armor layer, and this is expected to contribute to the design of stable natural channels, which can minimize the cost of irrigation canal maintenance and development. Doi: 10.28991/CEJ-2022-08-06-01 Full Text: PDF

End-to-end prediction of multimaterial stress fields and fracture patterns using cycle-consistent adversarial and transformer neural networks

The prediction of stress, strain fields or fracture patterns, along with other physical quantities as a function of boundary conditions and material microstructure, is an important objective of various physics-based simulation methods like finite element models or molecular dynamics modeling. However, such simulations may be expensive and can be costly in their execution, limiting their application to solve inverse design problems, or in the discovery of novel materials that feature a desirable performance. In other fields of studies, such as in mechanobiology, field data can often not be calculated due to a lack of models to begin with; where experimental observations may be the only source of insight. Here we introduce a data-driven method to relate input microstructures and field data using an alternative approach, enabled by deep learning, to predict complex mechanical fields directly based on input microstructure data. We report two approaches to solve said problem, first using cycle-consistent adversarial neural networks trained on unpaired images of microstructures and physical fields, and second, using a Perceiver neural networks based on an attention mechanism based on paired images, implemented in a transformer neural network. Due to the cycle consistent nature of the GAN model we can immediately make forward (from microstructure to stress field) and backward (from stress field to microstructure) predictions, offering an avenue for inverse material design. The Perceiver model, implementing an efficient transformer model that can be scaled to very large input and output data, shows strong generalizability and can be successfully applied to scenarios distinct from those in the training set. We demonstrate the model in several sample microstructures including a set of small cracks (voids) to predict both stress fields and fracture patterns, as well as in a composite microstructure of a soft matrix and rigid inclusions, and in a series of solutions to the inverse problem facilitated by the cycle consistent GAN model. The applications of the models include biomimetic biotechnology (e.g. bone-tendon-inspired attachments and gradients), armor materials, mechanobiology, soft robotics, and lightweight resilient and tough structural systems.

Thermo-structural analysis of ITER divertor for normal operating conditions

The ITER divertor serves as a plasma exhaust and is designed to handle very high heat loads and during the operation of ITER machine. The design of the divertor and its components are thus critical for the successful operation of the ITER machine. Tungsten is used as the armour material along with copper for the heat sink serve as Plasma facing components (PFCs) to sustain the high heat fluxes during steady state as well as off normal conditions. The PFCs are supported by high grade stainless steels that also sustain high structural and thermal loads due to Neutronic heating and heat fluxes. A thermo-structural analysis is performed for the ITER divertor and its components for steady state operating conditions to estimate the loads acting on different parts of the ITER Divertor. Heat loads due to neutronic heating has also been considered for the analysis.

Proposed Novel Eco-Friendly Natural Fiber of Gnetum Gnemon for Military Grade Applications

This paper investigates a tensile strength and microstructure characterization of Gnetum gnemon as a newly proposed eco-friendly natural fiber for composites reinforcement. Natural fibers have recently become attractive to researchers, engineers and scientists as an alternative reinforcement for composites. It has relatively low cost, renewable (easily available), and biodegradable. The production system requires simple and energy-efficient equipment and can be exploited as a replacement for the conventional fiber, such as Kevlar for personnel protection. The strength of Gnetum gnemon was found to be comparable with existing new composites. The form of fiber was found to be depended on the lignin, hemicellulose, benzene, and other impurities, thus made it larger and not uniform. These results show great potential as a competitor to the predecessor natural fibers used in composite materials of armor materials, if given special chemical treatment to increase their initial mechanical properties.

Dynamic response of a Li2O-Al2O3-SiO2 transparent glass-ceramic under shock compression

Li2O-Al2O3-SiO2 transparent glass-ceramics (LAS-TGCs) are promising candidates for transparent armour materials due to their excellent physical and mechanical capabilities. In this work, the dynamic behaviour of a LAS-TGC were further investigated using the planar impact technique and photon Doppler velocimetry. The shock stress, shock wave velocity, failure wave velocity and spall strength were obtained. In addition, the recompression signal, as a signature of failure waves, was observed to evolve into an oscillation signal as the impact stress decreases, indicating that the failure wave is gradually formed at a threshold. It has been noted that the failure wave velocity decreases with the increase in external loading and then turns upwards. The damage parameter of the LAS-TGC was assessed to be 0.410(5) under a shock stress of ~5.5 GPa, which is smaller than that of K9 glass. It is suggested that the LAS-TGC has better shock resistance than K9 glass.

Probabilistic analysis of cleavage fracture in commercial polycrystalline tungsten

Polycrystalline tungsten is a promising candidate as plasma-facing armour material in future fusion reactors. Below the DBTT tungsten shows brittle or semi-brittle behaviour with no or little plastic deformation before cleavage fracture. Moreover, tungsten has an inherent low fracture toughness as well as a large scatter within the strength properties. This requires a statistical treatment of the strength values. Therefore, four-point bending tests in the temperature range of room temperature (RT) to 400 °C were performed to allow the Weibull analysis in brittle failure regime and/or the Beremin model analysis in case of onset of plastic behaviour while approaching the DBTT temperature. The analyses are supported by FE simulations. Weibull and Beremin parameter values are determined from the simulation results using post-processing codes.

Simulation analysis of metal sheath and Armor loss of DC submarine cable based on COMSOL

The construction of submarine cable is recognized as a highly complex and difficult subject and project all over the world. Due to the special environment of the seabed, the submarine photoelectric composite cable needs protection. So armor was added. This makes the structure more complex and restricts the current carrying capacity. The loss of armor and metal sheath is the key factor restricting the current carrying capacity. Based on the finite element analysis method and COMSOL Multiphysics, this paper simulates and analyses the single core DC cable, and quantitatively explores the influence of different properties of armor materials on metal sheath and armor loss. It is concluded that the relative permeability of steel wire armor has a greater impact than conductivity in practical engineering, and the total loss of cable tends to be stable under high permeability. It has practical value and special significance for cable engineering construction.

Gas pressure casting technique for manufacturing of W/OFHC-Cu monoblock

The important engineering part of the divertor vertical target is the quality of joint between armor materials and heat sink. To reduce the joint interface stresses, a pure copper (Cu) interlayer was provided between the tungsten(W) armor and the CuCrZr cooling tube. Gas pressure casting method was developed to reduce the porosity and improve the mechanical properties of the Cu interlayer of W/Cu monoblock. In the vacuum casting sample without pressure, porosities were found in Cu. These porosities become defects at the interface between W and Cu and decrease the mechanical properties of the Cu interlayer. In the cooling process of casting, argon gas was pressurized into a porous tube inserted in the Cu and tungsten monoblock applying perpendicular force on the joint surface. This method was effective to remove the porosity in Cu generated during the cooling process and to increase the bonding strength between Cu and tungsten. The quality of bonding interface, depth of the Cu diffusion, and hardness of Cu were compared by SEM, EDS, and Vickers hardness measurement. In the samples made by gas pressure casting method, the porosity was decreased in Cu, no defects on the interface between tungsten and Cu, Cu was diffused into tungsten with a depth of 2∼3 μm and the hardness of Cu was increased about 15%.Small mock-ups were manufactured by hot radial pressing (HRP) with gas pressure casted W/Cu monoblock and CuCrZr cooling tube and underwent high heat flux (HHF) of 10 MW/m2 up to 5,000 cycles. The ultrasonic test (UT) results before and after the HHF test showed no defects on interfaces and was confirmed by observation of SEM on the cutting surface of the monoblock mock-up after the HHF test.