Soft Body Armor Research Articles

Research on high-velocity ballistic impact of para-aramid sateen fabric with ZnO nanorods oriented to the development of soft body armor

This study introduces an innovative approach of utilizing ZnO nanorod growing technology to the sateen fabric in order to improve its ballistic performance. Through SEM, FTIR, XRD and XPS analyses, ZnO nanorods with majority length of 1000–1500 nm and fineness of 200–600 nm have been deposited on the surface of sateen fabric surface Compared the fabric with ZnO nanorods (S-11-Nrs) with its neat counterpart, the mechanical properties of S-11-Nrs are increased, especially the inter-filament friction and fabric tensile breaking strength. However, in the impact process, the number of filaments involved in the impact is reduced and the filaments are mainly failure by the shear action of the bullets. Due to these positive and negative effects, the energy absorption of S-11-Nrs displays inferior ballistic energy absorption. Nevertheless, at lower areal density, in the non-perforation test, S-11-Nrs presents less BFS and shows better resistance to the consecutive shotting process compared with the neat fabric. The reason is that the increase of inter-filament friction limits the movement of filaments and thus results in less BFS. In addition, the flexibility, air permeability and moisture permeability are still kept. This research offers valuable insights for the design and development of comfortable soft body armor.

Facile armour production from cocoon waste by a cold-pressing process

Utilising cocoon waste as reinforcement in composites offers a cost-effective alternative for soft body armour production. Cocoon waste, including damaged or uncoiled cocoons and those with pupae, is recognised as an eco-friendly choice. This study aims to develop and assess the incorporation of varying amounts of cocoon waste as reinforcement in epoxy resin matrix composites through the cold-pressing process. The cocoon waste content in the composite specimens ranged from 0 to 40 wt%. Tensile testing and ballistic impact testing were conducted to evaluate specimen performance. The cocoon waste composite plate exhibited a maximum tensile strength of 62.21 MPa at 30 wt%, slightly surpassing that of woven hemp. These findings indicate the advantageous reinforcement attributes of cocoon waste. However, a limitation was identified: bullets fully penetrated the composite plate. To address this, ultra-high-molecular-weight polyethylene was incorporated into cocoon waste composites, resulting in enhanced tensile strength (107.36 MPa) and complete bullet penetration prevention. These outcomes position the study as a promising avenue for developing body armour plates meeting the stringent level II certification standards set by the National Institute of Justice.

Behind Armor Blunt Trauma: Liver Injuries Using a Live Animal Model.

While the 44-mm clay penetration criterion was developed in the 1970s for soft body armor applications, and the researchers acknowledged the need to conduct additional tests, the same behind the armor blunt trauma displacement limit is used for both soft and hard body armor evaluations and design considerations. Because the human thoraco-abdominal contents are heterogeneous, have different skeletal coverage, and have different functional requirements, the same level of penetration limit does not imply the same level of protection. It is important to determine the regional responses of different thoraco-abdominal organs to better describe human tolerance and improve the current behind armor blunt trauma standard. The purpose of this study was to report on the methods, procedures, and data collected from swine. Live swine tests were conducted after obtaining approvals from the local institution and the Army Care and Use Review Office of the U.S. Department of Defense. Trachea tubes and an intravenous line were introduced before administering anesthesia. Pressure transducers were inserted into the lungs and aorta. An indenter simulating the backface deformation profiles produced by body armor from military-relevant ballistics to human cadavers was used to deliver impact loading to the liver region. A triaxial accelerometer was included in the indenter design. The animals were monitored for 6 hours, necropsies were performed, and injuries were identified. Biomechanical data of the energy, velocity, deflection, viscous criterion, force, and impulse variables were obtained for each test. Peak accelerations, velocities, deflections, forces, impulse, and energies ranged from 897 to 5,808 g, 21 to 59 m/s, 1.96 to 8.87 cm, 2.3 to 13.1 kN, 1.1 to 7.1 Ns, and 58 to 387 J, respectively. The peak viscous criterion ranged from 0.8 to 5.8 m/s. All animals survived the 6-hour survival period. Three animals responded with liver lacerations while the remaining 4 did not have any injuries. The experimental design based on parallel tests with whole body human cadavers and cadaver swine was found to be successful in delivering controlled impacts to the liver region of live swine and reproducing liver injuries. Previously used biomechanical measures as potential candidates for injury criteria development were obtained. Using this proven model, tests with additional samples are needed to develop injury risk curves for liver impacts and obtain regional (liver) injury criteria.

Design, Fabrication and Performance Test of an Effective Body Armor

Aims: This original research paper targets an easy but efficient design and fabrication of a safe body armor. A test bed with weapons was another key aim. Therefore, it is essential to verify the vest’s capability to withstand rigorous stab tests as prescribed by the standard. Background: The most widely used armor piece is the torso-protecting overt (worn over the uniform or clothing) one. The main concern of this work was to design and develop such a stabresistant soft body armor made from readily available materials to protect against threats such as knives, blades, and sharp-tipped objects. Objectives: From the Mechanical Engineering point of view, the present research goals for such an armor vest were: low cost, moderately lightweight, comfortable, made from easily available materials, simple forward design, easy to fabricate, and the ability to adjust the level of protection without altering the primary design structure. The effectiveness of the vest needed to be verified through rigorous testing following relevant standards. Methods: The prototype of the stab-resistant armor was fabricated with two different configurations and their performance was rigorously tested in accordance with the NIJ Standard-0115.00 to determine its level of protection. Nylon-based panel elements covered with rubber and cotton-based panels were compared in terms of their ability to stop stab threats. Taking into account the key point of strike energy levels during the stabbing, test beds were created in the laboratory to rigorously conduct the required tests. Blades of two types were made, attached with fixtures, and dropped on the armors (upon backing material) in the test bed. Results: The ‘Complete Armor’ showed excellent performance against stab attacks. The tests revealed that the nylon-based panel elements covered with rubber were more successful in stopping stab threats compared to cotton-based panels. Conclusion: The designed and fabricated prototype of the stab-resistant soft body armor achieved the desired level of protection against stab threats. The armor is also cost-effective, it can be fabricated using locally available materials, at a cost of only 10 USD compared to 300 USD for commercially available armor. Other: However, it should be noted that stab resistance does not necessarily imply ballistic resistance, and no armor can provide invincibility against all types of threats.

Simulation of the Performance of Kevlar Impregnated Shear Thickening Fluid Ballistic Test Results (STF) Ballistic Test Results

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.

The impact of boron carbide in soft and hard body armor: A comprehensive evaluation on Kevlar and UHMWPE fabrics

AbstractIn this research, an investigation was conducted to ascertain the impact of boron carbide (B4C) microparticles on soft and hard armor configurations, utilizing two distinct high‐performance fabrics namely, Kevlar and Ultra‐high Molecular Weight Polyethylene (UHMWPE), also this work discerned the optimal fabric for protection against dagger attacks and 9 mm full metal jacket (FMJ) projectiles. Initially, rheological tests on four shear thickening fluid (STF) samples revealed that 70% of nano‐silicate (SiO2) content was the optimal ratio. Besides, scanning electronic microscope (SEM) tests showed that B4C affected the nano‐silicate dispersion. Hence, the use of STF as a matrix, led to complete protection in low‐velocity stab test and behavior improvement when subjected to NIJ ballistic test for both fabric types. On the other hand, the dynamic mechanical analysis (DMA) of the thermosetting epoxy resin‐based composites reinforced by B4C indicated that the 10% ratio offered maximum rigidity, resulting in improved ballistic performance. This study revealed that Kevlar fabrics exhibit superior behavior in soft protection, while UHMWPE hard composite display further rigidity against high‐velocity impacts. Overall, this work contributes novel insights into the efficiency of B4C integration within soft and hard armor configurations using two ballistic fabrics, highlighting their performance characteristics in ballistic shielding.Highlights Investigation of B4C microparticles: The research examines the impact of B4C microparticles on soft and hard armor configurations. High‐performance fabrics: Kevlar and UHMWPE uses. The use of STF as a matrix for soft and thermosetting epoxy resin for hard armor: enhanced composite performance. Low‐velocity and high‐velocity impact tests investigations; microparticles B4C incorporation: superior mechanical characteristics. Remarkable energy absorption: promising shielding uses.

A design model of multi-layer modified aramid fabrics against fragment simulating projectiles and full metal jacketed bullets

Soft body armor is required to meet threats of both bullets and explosion fragments in battlefield. However, designing body armor that can protect against these two types of projectiles considering both critical velocity and back face deformation (BFD) is often based on experience and extensive ballistic experiments. This paper proposes a quick design model for determining the layers of aramid fabrics modified by polyethylene (PE) to protect against fragment simulating projectiles (FSP) and full metal jacketed bullets (FMJ). Firstly, ballistic experiments are conducted discovering the optimal concentration of PE modification against the sphere and FSP is 10 %. Secondly, finite element model is adapted to explore the protection capabilities of modified aramid fabrics against FSP and FMJ and a linear relationship between the BFD and the critical velocity has been observed. Thirdly, an analytical model is established to uncover the reason of this relationship. Finally, a design model is proposed to configure the improved outer tactical vest (IOTV) generation III based on the derived formulae of critical velocity and BFD for different layers of modified aramid fabrics against FSP and FMJ. The model indicates that the objectives of intercepting FSP or FMJ and reducing blunt trauma are usually not simultaneously attainable. 38 layers of modified aramid fabrics are sufficient to meet the protection requirements for both FSP and FMJ, regardless of critical velocity and BFD. Besides, 498 m/s is the threshold of FMJ impact velocity to determine the priority of intercepting bullets or reducing blunt trauma. The design model can serve for the development of lightweight and effective body armor.

A hybrid approach of NiP coating and STF impregnation of UHMWPE fabric for conductive soft body armor

To enhance the ballistic impact performance and impart electrical conductivity into soft armor material made up of UHMWPE fabric, a novel hybrid technique has been devised and incorporated. Initially, the NiP layer was deposited on the UHMWPE fabric surface through the electroless process, subsequently, it was impregnated in the shear thickening fluid (STF) based on nano-silica (40 wt%). The morphology, functional groups, phase structure, thermal stability, breaking load, inter-yarn friction, electro-heating, and ballistic impact performance of the neat (UHM), STF impregnated (UHM-STF), NiP coated(UHM/NiP), and NiP coated STF impregnated (UHM/NiP-STF) fabrics are detailed. The NiP coating enhanced the ballistic impact performance, and thermal stability, and became electrically conductive compared to neat fabric. The ballistic impact test confirmed the enhancement in the energy absorption of UHM-STF (30.84%), UHM/NiP(18.37%), and UHM/NiP-STF(54.82%) compared to UHM. The hybrid technique (UHM/NiP-STF) exhibited higher inter-yarn friction (53.79%) and ballistic impact energy absorption (18.43%) compared to UHM-STF. The significant rise in the impact energy absorption of the UHM/NiP-STF can be ascribed to the synergetic effect of enhanced inter-yarn friction induced by the NiP-coated layer and the shear thickening behavior exhibited by STF. The NiP-coated and STF-impregnated fabrics present a promising prospect for the advancement of soft body armor materials with multifunctional ability.

Dynamic measurement of ballistic impact using an optical fibre sensor

An optical fibre-based sensor is developed for measuring the dynamics of the back face deformation of soft body armor. The measurement system consists of embedding an optical fibre into a thin silicone mat to increase survivability. The silicone sensor mat is placed between the soft body armor and the backing material. The optical fibre experiences times of sticking and slipping. The portions of the impact with the optical fibre stuck are reconstructed into slipping-equivalent strain using exponential extrapolation from adjacent slipping portions. The strain on the optical fibre is related to the projectile acceleration when the optical fibre is slipping. The strain is measured with the optical fibre sensor using a fibre Bragg grating. The system is characterized using a gas gun in combination with high-speed imaging. The system is experimentally demonstrated at the Army Test Center in Aberdeen, MD. Of the 23 shots 17 had an error less than 10%.

Revolutionizing protective materials: Ultrahigh peak viscosity through MOF-enhanced shear thickening fluid for advanced soft body armor

The incorporation of shear thickening fluid (STF) into aramid fabric has emerged as a compelling strategy to augment the protective attributes of aramid-based soft body armor. The peak viscosity of STF assumes a pivotal role in shaping the efficacy of this enhancement. In this study, we present an innovation in the design and synthesis of an ultrahigh peak viscosity STF using metal-organic framework (MOF)/SiO2 nanoparticles as the core constituents. The remarkable enhancement in peak viscosity of MOFs/SiO2-based STF, taking ZIF-8 as an exemplary MOFs material, is attributed to the pronounced interparticle contact friction facilitated by the rugged surface morphology of the ZIF-8/SiO2 nanoparticles. Therefore, ZIF-8/SiO2-based STF (62.5 wt.%) demonstrates a peak viscosity approximately 3938 times greater than that of conventional SiO2-based STF (62.5 wt.%). This extraordinary STF formulation has been successfully employed in aramid fabric-based soft body armor, resulting in a significantly advancement in protective performance. Compared to Kevlar fabric impregnated with SiO2-based STF (62.5 wt.%), the utilization of ZIF-8/SiO2-based STF (62.5 wt.%) results in substantial and scientifically significant improvements in key mechanical parameters. These include a notable 15.4 % increase in maximum stabbing force, a remarkable 29.5 % augmentation in maximum yarn pull-out force, a 24.3 % boost in maximum yarn tensile strength, and a 204.5 % enhancement in maximum fabric tensile strength. This research underscores the profound impact of synergizing ZIF-8 and SiO2 within the STF matrix, and significantly improves the protective abilities of SiO2-based STF-impregnated Kevlar fabrics, which provides a new route to design STF-impregnated ballistic fabric with high protective performance.

Enhancement of silk fabric knife-stabbing resistance for soft body armor

Traditional silk, known for its strength, flexibility, and comfort, shows promise as a lightweight, comfortable material for stab-resistant armor. This study explores enhancing silk’s knife-stabbing resistance for soft body armor through surface treatments. This study aims to augment the knife-stabbing resistance of silk fabric for soft body armor. Designed a falling tower setup to investigate fabric responses under impact. Exploring the addition of layers with coatings like silicon dioxide deposition, rice ash deposition, and aluminum oxide particles, the investigation revealed significant enhancements. A solitary silk layer exclusively coated with resin exhibited improvements of approximately 37.07%, 29.21%, and 13.47% in stab resistance for rice ash, aluminum oxide, and silicon oxide particles, respectively. The specific knife penetration depth indicated that the coating is more effective in diminishing penetration depth. The research identified that 7 layers of pure silk and 3 layers coated with rice ash satisfy National Institute of Justice Standard–0115.00, S1 as 26 layers of silk fabric, demonstrating a reduction without compromising protective efficacy.

Gradient shear thickening gel/Kevlar fabric multi-layer armor with enhanced impact attenuation property

Realizing highly-efficient energy absorbing performance in soft body armor, yet with lightweight feature, has always been an eternal subject for personal protective equipment. This work reports a gradient-stacked shear thickening gel (STG)/Kevlar (GS-STG/Kevlar) fabric multi-layer armor with both lightweight feature and excellent impact attenuation performance. Firstly, STG is prepared by mechanical blending and chemical crosslinking and then coated on Kevlar fabrics, and afterwards STG-coated multi-layer Kevlar fabrics with gradient STG distribution in the thickness direction are fabricated. Single yarn pull-out test demonstrates that the friction between Kevlar yarns is greatly increased after STG treatment. Moreover, tribological testing also indicates that the friction coefficient of Kevlar fabrics is improved by coating STG. Furthermore, low- and high-speed impact experiments are conducted, and the results demonstrate that the GS-STG/Kevlar fabric composite exhibits the best impact attenuation property when compared with multilayered Kevlar fabrics and uniformly stacked STG/Kevlar fabrics under the same impact conditions. The increased friction and stiffening effect by STG, and the gradient stacking strategy are responsible for the great improvement in the impact attenuation performance of GS-STG/Kevlar fabric multi-layer armors. This study provides an effective methodology for achieving soft body armors with lightweight and high impact attenuation properties for personal impact protection.

Development of sansevieria trifasciata/natural rubber composites for a soft body armor application

Body armor is an indispensable material in the military and defense. The development of body armor nowadays has shifted to lower-cost material with comparable ballistic properties. This research studied the potential of sansevieria trifasciata (ST) fiber as a reinforcement in soft body armor composite. The ST fiber was treated with various NaOH concentrations to achieve the highest tensile strength. The result showed that the highest ST fiber strength was achieved at 1.2GPa by treating the fiber with 1 wt% NaOH solution. The rebound resilience properties of the natural rubber (NR) matrix were optimized by varying the accelerator and carbon black content and were tested according to ISO 4662. The optimum energy absorption of the NR matrix was obtained using 0.4 part per hundred rubber (phr) accelerator and 30 phr carbon black. The ballistic performance of ST/NR composites was evaluated through a simulation using LS-DYNA software. The ballistic simulation revealed that the minimum thickness of ST/NR composite was 15mm to stop a bullet with a velocity of 436m/s. The results of this study indicated that ST/NR green composite was a promising candidate for a soft body armor application.

Numerical and experimental investigation of the ballistic performance of hybrid woven and embroidered-based soft armour under ballistic impact

One approach to developing more effective soft body armour is to modify the structure of the ballistic packages. Typically, soft ballistic packages are formed as a multilayer system composed of woven fabrics or flexible unidirectional sheets, also in hybrid combinations. It should be noted that relatively little is known about ballistic packages composed of embroidered structures. This article presents the results of numerical and experimental studies of the ballistic efficiency of packages composed of para-aramid embroidered structures and woven fabrics fixed at all four edges after firing with a 9x19 mm FMJ Parabellum projectile at an impact velocity of 380 m/s. Numerical modelling was used both to assess the ballistic efficiency of the packages in various hybrid constructions and to optimize the structure of the most efficient hybrid construction of the package. Based on the results of numerical and experimental studies, it was shown that hybrid packages containing fabrics on the impact side of the projectile and structures embroidered on the back are significantly more efficient than the reverse combination. The optimization carried out showed that the most efficient package should contain a number of woven layers equal to twice the number of penetrated layers on the projectile impact side.

Body Armor-Inspired Double-Wrapped Binder with High Energy Dispersion for a Stable SiOx Anode.

The high specific capacity and relatively low volume expansion of silicon suboxide (SiOx) highlight its potential as one of the most promising anode materials for lithium-ion batteries. Nevertheless, the traditional binder of polyacrylic acid (PAA) still cannot adapt to enormous stress during the repeated volume expansion/contraction owing to its intrinsic rigid backbone. Inspired by the "soft and hard composite body armor", we herein design a double-wrapped binder consisting of PAA with a high internal Young's modulus (hard part) and polyurethane (DOU) with a low external Young's modulus (soft part). When the SiOx particle expands during lithiation, the rigid PAA firstly accommodates the volume change to dissipate most of the inner stress, and the elastic DOU with triple dynamic bonds serves as a buffer layer to absorb the residual stress via the breakage/formation of dynamic bonds. By optimizing the PAA/DOU ratio, the SiOx anode can maintain the integrity during long-term cycling and deliver a relatively high reversible capacity of 1064.1 mAh g-1 with a preeminent capacity retention of 83.7% at 0.5C after 300 cycles. Such a double-wrapped binder can provide a novel design strategy for multicomponent functional polymer binders toward high-performance SiOx anodes.

Quantification of time-dependent deterioration in mechanical property and ballistic performance through Cunniff Number of poly (p-phenylene terephthalamide) fibers under UV irradiation

Poly (p-phenylene terephthalamide) fibers, a crucial constituent of soft body armor, experience significant deterioration in mechanical and ballistic performance due to UV exposure. However, photo-degradation by UV radiation involves complex chemical reactions and the difficulty in estimating the extent of damage that restricts the development of the predictive aging models or kinetics in such fibrous materials. Hence in this work, the photo-degradation kinetics of poly (p-phenylene terephthalamide) or KF-fibers is quantified by correlating the degradation behavior of different properties with time, thereby assessing the useful performance span of the UV-aged (UV-KF) fibers. The experimental trends indicate three stages of deterioration of any property (modulus, extension at break, Cunniff Number and crystallinity), i.e., an exponential decline followed by an increase over a short duration and finally, a steady and continuous drop. The suitable performance period of UV-aged fibers is estimated based on the initial two stages and presented as ‘favorable property region’ or ‘FPR-zone.’ Changes in V50 ballistic limit, theoretically derived from Cunniff Number, are also estimated, which show a good agreement with the literature data. It reveals that the energy absorption capacity of UV-KF fibers corresponds to initial two years as a span of considerable ballistic protection before continuing to function at 50% of its original protection level for lower aging temperatures. Besides, the apparent activation energy for all the studied properties is correlated to the microstructural and physico-chemical aspects. It indicates that relative changes in molar mass by bond scission/rearrangement and alterations in crystallinity are proportionally related to the degree of variation in modulus and extension at break, thus affecting the wave-velocities in terms of Cunniff Number. The proposed degradation model further can be extended to determine the rate of degradation and lifetime of various ballistic materials under other environmental conditions.

Theoretical model for predicting stabbing resistance of soft body armor comprising fibrous composites

Soft body armor can effectively safeguard lives from stabbing attacks and they are mainly composed of fibrous composites. Currently, the evaluation of protective performance for soft body armor is mainly conducted by experiments or numerical simulations, with theoretical methods have been rarely mentioned. In this study, a spring-mass based theoretical model has been established to predict the stabbing resistant performance of a soft body armor comprising aramid with resin or unidirectional UHMWPE composites. The theoretical results agree well with the experimental results where the error in maximum impact force of the knife is within 3.2% and the displacement within 1.7%. The layers of penetration are also identical. By only inputting hardness and stiffness of the specimen, the theoretical model can efficiently provide the performance of a soft body armor composed of fiber composite material under different impact energy levels. With the aid of this theoretical model, one can optimize the composition of a soft body armor to achieve minimum weight and thickness in practical applications.

Low-Temperature-Tolerant Strain-Sensing Flexible Composite for Soft Body Armor.

Developing soft body armor with sensing characteristics in various application scenarios is a challenge but important for creating a peaceful world and personal safety, whereas existing materials suffer from indefinite protective effects and stimulus response at subzero temperatures in the long term. Herein, an anti-freezing and flexible puncture-resistance composite with strain-sensing ability is developed by compounding a NaCl-soaked poly(vinyl alcohol) (PVA)/sodium alginate (SA)/glycerol (Gly) hydrogel (PSGN hydrogel) with Kevlar fabric. After freezing-thawing treatment once and NaCl immersion for 10 h, the Kevlar/PSGN-10 composite has excellent puncture-resistance properties and linear, rapid response, wide band, and stable strain-sensing behaviors at 25 and -30 °C. The composite's maximum puncturing force and energy dissipation at -30 °C are 53.92 N and 370 mJ, respectively, increased by 285 and 302% compared with neat Kevlar fabric. The flexibility reduction and the mass addition of the Kevlar/PSGN-10 composite are merely 19 and 40%, respectively, showing superior wearable comfortability and protection efficiency. The composites also reveal remarkable strain-sensing abilities at -30 °C (linear strain sensitivity with GF = 0.27 and R2 = 0.981, a wide working frequency range of 0.16-1.3 Hz, and sensing stability for 1500 cycles). Moreover, the composite could respond to multipart body motion directly, including fingers, elbows, wrists, and knees. Consequently, the Kevlar/PSGN composite developed in this paper is promising for intelligent soft body armor at various temperatures.

Numerical investigation of the high-velocity impact performance of body armor panels

The body armor can effectively reduce penetration injuries and save many soldiers’ lives. However, back face deformation (BFD) accompanied by ballistic impacts on body armor can lead to fatal injuries to soldiers on the battlefield. In the study, ballistic tests and finite element models are performed to evaluate the protection of body armor panels. Both soft body armor and ceramic till are validated against the experimental data. Then, the performance of the ultra-high molecular weight polyethylene (UHMWPE) soft armor incorporating the RP #1 clay and foam pad is discussed. The simulation results show that the addition of a foam pad can effectively reduce the maximum clay BFD. At the same time, the performance of the ceramic-UHMWPE panel is studied. The ceramic tile can partly absorb the kinetic energy of the high-velocity projectile and enlarge the contact area between the UHMWPE panel and RP #1 clay, which leads to a lower BFD value. In addition, the effects of the interlaminate strength and the laminate stacking direction of the UHMWPE panel on the BFD are discussed. The current simulation can capture the damage behavior of UHMWPE laminates and ceramic tile well, which can be a guide for the design and improvement of new body armor panels.

Investigating the effect of aligned Ag nanorods on para-aramid woven fabric and anisotropy in inter-yarn friction

Inter yarn friction, measured in terms of yarn pull-out force, is a major mechanism of energy absorption in soft body armor. Increasing inter-yarn friction of para-aramid fabric to improve ballistic performance without adding weight is challenging. This work reports the fabrication of aligned Ag nanorods (AgNRs) on the para-aramid (Kevlar) fabric surface using the glancing angle deposition technique. A single yarn pull-out test examines Kevlar fabric treatment. The AgNRs-coated para-aramid fabric retains its flexibility and weight while increasing yarn pull-out force by 130%. Anisotropy in inter-yarn friction depends on the yarn's sliding direction relative to Ag nanorod tilt direction, indicating direction-dependent yarn pull-out force. The periodic character of pull-out response post-peak force is replicated by modeling the yarn pull-out phenomenon by incorporating a mesoscale level numerical model of woven fabric. The numerical model confirms the experimental results that formation of nanorods significantly increases inter-yarn friction and pull-out force.