Aramid Fabrics Research Articles

Impact resistance of aramid honeycomb tandem sandwich composites reinforced with TiB2

A novel composite tandem sandwich structure made of aramid fabric and aramid honeycomb, impregnated in a matrix of epoxy resin combined with poly (vinyl butyral), PVB, is proposed. The composite was additionally reinforced with a small concentration of titanium diboride nanoparticles, TiB2, to study its effect on impact resistance. Sandwich composite samples were fabricated by impregnating the aramid fabrics and honeycomb in subsequent layers with the system epoxy/PVB/TiB2. Their mechanical behavior was examined through three-point bending test, Charpy impact test, and compressive test. The chemical reaction between PVB and epoxy resin, and chemical inertness between the nanoparticles and the other constituents were confirmed by FTIR analysis. The flexural strength and stiffness increased by 27.6% and 62.5%, respectively, in the presence of TiB2 reinforcement. Impact tests showed increase of 104% in impact toughness in the case of samples with TiB2. Nano TiB2 did not increase compressive strength of the proposed sandwich structure, but it improved its stiffness and reduced the permanent deformation. The achieved improvements in mechanical resistance make this new composite structure a promising candidate for automotive, airspace, naval, civil engineering, sports equipment industry, and for use in defense technologies.

Composite waste-based aramid aerogel separators

Lithium ion batteries are one of the most promising electrochemical energy storage systems. They generally consist of four components: anode, cathode, electrolyte, and separator. The separators are crucial for batteries since they prevent physical contact of electrodes and thus short circuit. In this study, reutilization of aramid fabric was highlighted by transforming it into a high value product: battery separator. A waste aramid fabric was used to synthesize aramid aerogels by deprotonation, sol-gel, and freeze-drying processes and then investigated as lithium ion battery separators. Aramid fabric was collected from a scrap plant of an industrial automotive company. Nanoclay or TiO2 nanoparticles were added into this waste-based aramid aerogel matrix in the sol-gel stage to further enhance the performance of the separators. The samples were characterized by scanning electron microscope (SEM), linear sweep voltammetry, electrochemical impedance spectroscopy (EIS) and galvanostatic charge/discharge tests. A uniform and bead-free morphology was observed for all samples with over 60% porosity. Electrolyte uptake and ionic conductivity test results showed that addition of TiO2 nanoparticles increased electrolyte uptake and ionic conductivity up to 365% and 2.2 mS/cm, respectively. The cells prepared by using nanocomposite aramid aerogels with TiO2 exhibited excellent cycling performance with a capacity of around 160 mAh/g in 200 cycles.

A low-cost and large-area modular nickel electrode on aramid fabric for efficient solar-driven water electrolysis

We demonstrate a water electrolysis device consisting of two 10 cm2 Ni/aramid flexible electrodes with a Si solar cell with >13% solar-to-hydrogen efficiency over 120 hours stability.

Application of single and multi-solid phase STFs to Twaron fabrics: evaluation of energy absorption performances

The present study aims to enhance the energy absorption performance of Twaron aramid fabrics by impregnating them with single and multi-solid phase shear thickening fluids (STFs). To investigate the energy absorption capacity of Twaron 200 and Twaron 460 fabrics, surface friction, yarn tensile, and ballistic tests have been performed. Silicon carbide (SiC), graphene nanoplate (GNP), and carbon nanotube (CNT) are utilized both individually and in hybrid forms to examine the impact of multi-solid phase STFs. The research reveals that STFs reinforced with SiC and GNP exhibit higher viscosity and rheological behavior compared to other hybrid nanoparticles. The addition of SiC and GNP reinforced STF (STF/SiC + GNP) suspension significantly increases the friction coefficient by approximately 82% for Twaron 200 and 120% for Twaron 460 in comparison to neat fabric. Moreover, the maximum yarn tensile strength of Twaron 460 is higher than that of Twaron 200 in both neat and STF impregnated fabrics. The research also states that STF impregnation procedure improves the ballistic performance of neat fabrics in both fabric types. The ballistic test results show an increase in the protective performance of STF impregnated fabrics reinforced with nanoparticles. The best ballistic performance is found in STF/SiC + GNP impregnated fabrics in Twaron 200 and Twaron 460 samples.

Near simultaneous multiple fragment impacts on aramid fabrics: Effects of velocity, dispersion and time intervals

Protection against fragment impacts is a critical concern across various applications. Conventional standardised methods use single-impact tests as a simplified approach for evaluating material resistance against impacting fragments. An alternative, near simultaneous triple impact test was implemented for testing protective equipment and materials against fragmentation, effectively simulating the impact of a dense cluster of fragments. Aramid fabrics, the most common protective measure against fragments, exhibit up to 13 % reduced ballistic resistance under triple impacts opposed to single impact tests signifying the importance of a multi-hit test method when evaluating protection against fragments.In this article, a finite element model is developed to conduct a detailed analysis of the dynamic interactions within a triple impact test. This analysis decouples and isolates the various contributing factors, including: the impacting velocity, the dispersion between impacts, the impact positions with respect to the main axes of material symmetry and the time intervals between the impacting projectiles. The model describes 15 layers of aramid fabric, in a detailed discrete mesoscale format, subjected to single, dual and triple impacting 1.102 g Fragment Simulating Projectiles (FSP) in different configurations using the finite element package LS-Dyna.As anticipated, penetrability increases when the distance between two impacting projectiles decreases. Additionally, on-axis impacts are more likely to result in perforation due to increased stress wave destructive–constructive interferences. Furthermore, the time interval between impacts is found to play a major role on the target's eventual ballistic performance. The oscillating phase caused by the excitation from the preceding impacting projectile, can amplify or diminish the relative impacting velocity of the subsequent projectile by as much as 40 %, resulting in either an over-perforation with residual velocity 55 % of the initial impacting velocity, or no-perforation with 0 % penetration depth.

Synthesis and modification of poly (p‐phenylene terephthalamide) for production of light‐weight hybrid composite armors reinforced with polymer composite nanofiber mats

AbstractPoly (p‐phenylene terephthalamide) (PPTA) polymer was synthesized and then modified to eliminate the processing difficulties arising from its insolubility in organic solvents. The chemical structures of the synthesized PPTA and N‐butyl PPTA (BPPTA) were confirmed by elemental analysis, x‐ray diffraction, Fourier transform infrared (FTIR), and 13C‐NMR spectroscopy studies. As a result of modification, an aramid derivative that is soluble in some common solvents was obtained and added into polyacrylonitrile (PAN) matrix in solution. PAN/BPPTA composite nanofiber mats (CNMs) were fabricated by electrospinning. Mechanical tests showed that tensile strength increased by 119% with 3% BPPTA content. The fabricated CNMs were combined with aramid fabrics to produce laminated hybrid armors and ballistic tests were performed following the NATO Stanag 2920 standard. This is the first report about the integration of CNMs into multilayer armor configurations and resulted in improved ballistic limit velocity (V50) with a relatively very small weight gain and emergence of new energy absorption mechanisms.Highlights Alkylation of the para‐aramid yielded an organo‐soluble aramid derivative. Tensile strength of PAN nanofiber mat increased by 119% with 3% N‐butyl PPTA. Integration of the CNMs resulted in new ballistic impact absorption mechanisms. CNMs contribute to V50 with a very low mass gain due to their high surface area/mass.

AgNWs–Silane Coatings for the Functionalization of Aramid Woven Fabrics

Aramid woven fabrics are widely used to provide protection in extreme conditions, especially in high temperatures. Multifunctional aramid fabrics with no deteriorated thermal resistance and antibacterial properties are needed for high-risk professions. In this study, silver nanowires (AgNWs) and silanes (S) were used for the functionalization of meta- (mAr) and para-aramid (pAr) woven fabrics by mixture (Ag + S) or by the layer-by-layer (Ag/S) method. Antibacterial properties, thermal management, and stability were studied to select the functionalization method which provided the highest thermal performance, comfort, and bioactivity. Both methods decreased the fabric’s surface temperature during heating in the range of 35–40 °C by 3 °C and 2 °C, respectively, for mAr and pAr, in comparison to unmodified fabrics. After Ag + S and Ag/S modifications, the thermal degradation initial temperature increased from 554 °C to 560 °C (TG/DTG) and from 525 °C to 533 °C (DSC) for pAr fabrics, and decreased from 417 °C to 403 °C (TG/DTG) and from 411 °C to 406 °C (DSC) for mAr fabrics. The reduction in Gram− (Klebsiella pneumonia) and Gram+ (Staphylococcus aureus) bacterial growth for all modified samples was above 90%. The bactericidal and bacteriostatic coefficients were slightly higher for Ag/S functionalization. The highest thermal performance and antimicrobial activity were noted for pAr fabric modified using the Ag/S method.

PMD/TiO2 gel/aramid fabric synergistically toughened to build soft composites with high puncture resistance and rapid self-healing

To solve the problem of soft composites with both high puncture resistance and rapid self-healing. First, we used Pluronic F127 bisacrylate (PF127DA) as a micellar cross-linker, titanium dioxide (TiO2) as a nanoparticle cross-linker, and acrylic acid-2-methoxyethyl ester (MEA) and N,N'-dimethylacrylamide (DMAA) as monomers to prepare nanocomposite gels (PMD/TiO2 gel). On this basis, the soft composites were prepared by combining them with aramid fabrics. The results showed that the soft composites exhibited excellent fabric reinforcement and rapid self-healing properties, in which the force values for the spike and knife stabs are 242 N and 208 N, respectively, and the self-healing efficiency of the spike stab resistance is as high as 50 % and the self-healing efficiency of the knife stab is as high as 37 % after 80 min at 120 °C. In conclusion, this paper provides important guidance for the design of soft composites with high puncture resistance and fast self-healing capability.

Flexible Puncture-Resistant Composites for Antistabbing Applications: Silica and Silicon Carbide Nanoparticle-/TPU-Coated Aramid Fabrics.

In harsh environments, it is crucial to design personal protective materials that possess both puncture/cut resistance and chemical resistance. In order to fulfill these requirements, this study introduces an innovative approach that combines hydrophobically modified rigid nanoparticles with thermoplastic polyurethane elastomers. These materials are then laminated with high-performance aramid fabrics through a scraping process, resulting in a multifunctional composite with puncture/cut resistance, superhydrophobicity, self-cleaning properties, and acid/alkali resistance. The quasi-static puncture tests conducted reveal the remarkable performance of the composite. The maximum spike puncture resistance reaches 267.62 N, which is 17.14 times higher than that of the pure fabric (15.61 N). Similarly, the maximum knife puncture resistance reaches 115.02 N, exhibiting a 5.01 times increase compared to that of the pure aramid fabric (22.97 N). Furthermore, the results obtained from the yarn pull-out, fabric burst strength, and tearing experiments demonstrate that the incorporation of rigid nanoparticles significantly enhances the friction between the yarns, enabling a greater number of yarns to participate in the dissipation of impact energy. As a result, the puncture resistance of the fabric is greatly improved. Significantly, the composite exhibits sustained superhydrophobicity even after exposure to harsh chemicals such as concentrated sulfuric acid and sodium hydroxide as well as undergoing cyclic mechanical wear. These findings highlight the composite's exceptional durability and resistance to corrosion. Overall, this study offers insights and methods for the development of multifunctional flexible puncture-resistant equipment for individuals.

Determination of Energy Absorption Capabilities of Shear Thickening Fluid Impregnated Aramid Fiber Fabrics for Ballistic Applications

Low velocity impact behavior of shear thickening fluid (STF) impregnated aramid fabric having different number of layers had been investigating throughout this study to determine a relationship between number of layers and perforation energy. Firstly, STF solutions including polyethylene glycol, silica nanoparticles and ethanol were prepared by mixing a homogenizer. Solutions containing 20% silica nanoparticles by weight were used in this study. Rheological analysis was performed to observe thickening behavior of solution. After thickening behavior and critical shear rate was determined from rheological analysis, solution was impregnated into aramid fabric. Then, specimens having different number of layers from 1 to 8 were prepared for low velocity impact experiments. A drop weight impact test was applied at different energy levels and perforation energy was determined. Finally, a curve fitting equation was found to use it for potential energy absorption applications such as ballistic impact.

Bright structural colorful aramid fabrics with outstanding light fastness

AbstractThe problems of difficult dyeing, poor dyeing fastness, and dyeing pollution of aramid are always great obstacles in the practical application. In theory, constructing particular nanostructures instead of dyes on aramids to achieve bright structural colors will be an effective strategy. However, it is still challenging to construct particular nanostructures on aramid fabric surfaces because of their roughness. Here, beautiful and noniridescent structural colored aramids with excellent light fastness were achieved by spraying a thin layer of randomly distributed nanospheres on the surface of adhesive‐modified aramids. Moreover, different bright structural colors and colorful patterns were obtained by simply controlling the size or refractive index of the spheres. Importantly, the light fastness of the structural colored aramid can reach levels 6–7 or higher. The simple and eco‐friendly coloring technology can be compatible with industrial equipment to obtain stable multicolored aramid products, exhibiting great real potential applications.

Multi-Layer Fabric Composites Combined with Non-Newtonian Shear Thickening in Ballistic Protection-Hybrid Numerical Methods and Ballistic Tests.

Multi-layer fabrics are commonly used in ballistics shields with a lower bulletproof class to protect against pistol and revolver bullets. In order to additionally limit the dynamic deflection of the samples, layers reinforced with additional materials, including non-Newtonian fluids compacted by shear, are additionally used. Performing a wide range of tests in each case can be very problematic; therefore, there are many calculation methods that allow, with better or worse results, mapping of the behavior of the material in the case of impact loads. The search for simplified methods is very important in order to simplify the complexity of numerical fabric models while maintaining the accuracy of the results obtained. In this article, multi-layer composites were tested. Two samples were included in the elements subjected to shelling. In the first sample, the outer layers consisted of aramid fabrics in a laminate with a thermoplastic polymer matrix. The middle layer contained a non-Newtonian shear-thickening fluid enclosed in hexagonal (honeycomb) cells. The fluid was produced using polypropylene glycol and colloidal silica powder with a diameter of 14 µm in the proportions of 60/40. The backing plate was made using a 12-layer composite made of Twaron® para-aramid fabrics with a DCPD matrix-not yet used in a wide range of ballistics. Then, numerical simulations were carried out in the Abaqus/Explicit dynamic analysis. The Johnson-Cook constitutive strength model was used to describe the behavior of elastic-plastic materials constituting the elements of the projectiles. For the non-Newtonian fluid, a Up-Us EOS was used. The inner layers of the fabric were treated as an orthotropic material. Complete homogenization of the sample layers was carried out, thanks to which each layer was treated as a homogeneous continuum. As a parameter of fracture mechanics for shield components, the strain criterion was used with the smooth particles hydrodynamics method (SPH). Then, the results of simulations were compared with the results of the ballistic test for both samples placed next to each other, which resulted in the formation of a multi-layer composite in one ballistic test subjected to impact loads during firing with a 9 × 19 mm Parabellum FMJ projectile with an initial velocity of 370 ± 10 m/s. The results of numerical tests are very similar to the ballistic tests, which indicates the correct mapping of the process and the correct conduct of layer homogenization. The applied proportions of the components in the non-Newtonian fluid allowed a reduction in the deflection compared to previous studies. Additionally, the proposal to use a DCPD matrix allowed to obtain a much lower deflection value compared to other materials, which is a novelty in the field of production of ballistic shields.

Thermal Behavior of Curaua-Aramid Hybrid Laminated Composites for Ballistic Helmet.

Hybrid composites are expanding applications in cutting-edge technology industries, which need materials capable of meeting combined properties in order to guarantee high performance and cost-effectiveness. This original article aimed for the first time to investigate the hybrid laminated composite thermal behavior, made of two types of fibers: synthetic Twaron® fabric and natural curaua non-woven mat, reinforcing epoxy matrix. The composite processing was based on the ballistic helmets methodology from the North American Personal Armor System for Ground Troops, currently used by the Brazilian Army, aiming at reduced costs, total weight, and environmental impact associated with the material without compromising ballistic performance. Thermal properties of plain epoxy, aramid fabric, and curaua mat were evaluated, as well as the other five configurations of hybrid laminated composites. These properties were compared using thermogravimetric analysis (TGA) with its derivative (DTG), differential thermal analysis (DTA), and thermomechanical analysis (TMA). The results showed that the plain epoxy begins thermal degradation at 208 °C while the curaua mat at 231 °C and the aramid fabric at 477 °C. The hybrid laminated composites curves showed two or three inflections in terms of mass loss. The only sample that underwent thermal expansion was the five-aramid and three-curaua layers composite. In the third analyzed temperature interval, related to the glass transition temperature of the composites, there was, in general, an increasing thermal stability behavior.

An analytical model to predict back face deformation of hybrid soft body armors under ballistic impact

In the design of soft body armors for ballistic protection, the blunt trauma effect has to be taken into account and it is usually evaluated by the back face deformation (BFD). Most of the current research on blunt trauma is based on experiments and simulations, whereas the development of analytical models is still rare. This study develops an analytical model to predict BFD for a hybrid panel composed of modified aramid fabrics and Ultra-high molecular weight polyethylene (UHMWPE) unidirectional sheets, which is based on the two-stage damage evolution: shear plugging and tensile bulge. Firstly, the shear and tensile energy of the hybrid panel as well as the deformation energy of the clay were constructed. Secondly, the characteristic equations were developed according to the law of energy conservation and BFD could be obtained by solving the equations. The results of the analytical model were found to be in good agreement with experiments and FE simulations. With the assistance of the model, the effect of projectile geometry and optimized designs for hybrid panels have been studied.

Application of Neural Network for the Prediction of Loss in Mechanical Properties of Aramid Fabrics After Thermal Aging

Aramid fabrics are used to produce most of the flame resistant protection clothes to fulfil the protection requirements. Even though aramid fibers have good thermal stability and flame resistance properties, fabrics used in protective clothing age and loss some of their essential functions under various environmental and operational conditions during their lifetime. These conditions cause serious limitations in the use of clothing. In this study, various woven fabrics produced from aramid (Nomex, Kevlar) fabrics were exposed to accelerated aging tests under varying temperature and time period in order to construct Neural Network models to predict weight loss and tensile strength loss percentages of the fabrics. The results of Artificial Neural Network models demonstrate that regression values are 0.98405 for weight loss percentages and 0.99935 for tensile strength loss percentages of the fabrics. Accordingly, the proposed Artificial Neural Network models are correctly constituted and the losses in determined fabric properties is successfully predicted.

Studies of physio-chemical changes of dielectric barrier discharge plasma treated aramid fibers

Present work deals with the DBD plasma-induced surface modifications of aramid fabric for different exposure times and at atmospheric pressure using various characterization techniques such as XPS, ATR-FTIR spectroscopy and water contact angle measurements. Surface morphology using SEM reveals that, plasma treatment roughened the surface of the fabric. XPS results indicate that plasma treatment can successfully introduce polar functional groups onto the aramid fabric surface, improving its wettability and chemical reactivity. However, exceeding the optimal treatment time can result in the destruction of these functional groups and an increase in the C–C content, this can be attributed to the excessive etching of the surface and the destruction of the functional groups that were initially introduced during the plasma treatment. The ATR-FTIR spectra of plasma-treated aramid fabric show significant improvement in the intensities of CO and C–O stretching vibrations which relate to the wettability improvement. The results are discussed in the light of physical and chemical changes that occur due to DBD plasma treatment.

Variation of mechanical properties and ballistic performance of fabric prepreg after resin coating processing

This study aims to identify variation of mechanical properties and ballistic performance of fabric prereg after resin coating processing. An aramid fabric was coated with different resin ratio to obtain different fabric prepregs. Experimental tests and Finite Element (FE) simulations were conducted to investigate the role of resin coating. According to yarn pull-out test results, yarn mobility was restrained with increasing bonding force, which resulted in global deformation to the load. However, under ballistic impact, fabric prepregs displayed local failure and very limited Backface Signature (BFS). With increasing resin ratio, the tensile stress and energy absorption of the fabric prepregs was increased firstly and then decreased. In comparison with the neat fabric panel, the panel AF/R14 displayed the highest improvement of the tensile stress (16.28%) and specific energy absorption (21.5%). FE simulation results revealed the panel AF/R14 displayed obviously higher strain energy and frictional energy dissipation before failure than that of the neat fabric panel. When the fabric prepreg possessed appropriate bonding force, most of secondary yarns can be engaged in high strain (above 1%) during impact, which made great contribution to energy absorption as primary yarns. Therefore, resin coating on fabric can achieve improvement of ballistic performance.

Simulation of an Impact on an Aramid Fabric Panel by A .357 Projectile

Abstract This paper presents a model for impact bullet – panel of woven aramid fabrics in order to use it for an initial assessment of similar panels to protect against bullets in a range of 100…800 m/s. Based on these initial simulations, the designer could select the number of layers for actual tests. The factors that could be varied in these simulations could be the shape and dimensions of the projectiles, their mass and impact velocity. It is presented only the case of impacting a panel with .357 Magnum, with an incidence velocity of 420 m/s. The panel is composed of 8 layers of plain woven fabrics (200 mm x 200 mm), with weft and warp yarns, the yarn geometry being close to Teijin CT736 phenolic fabric, with 1680 DTEX and 410 g/m2. The simulation helps to identify the stages of panel failure and to evaluate qualitatively the similarity in panel failure with that of the actual panel, tested under the same conditions as the model.

Experimental evaluation of the ballistic resistance of aramid fabrics under near simultaneous multiple fragment impacts

The ballistic resistance of protective equipment against fragment impacts, such as those typically generated from explosions, has been a major concern the past 50years. The simplifications required to investigate the material response to multiple fragment impacts were set based on the technological limitations of the past. Still, current standardised ballistic testing methodologies consider the interactions between multiple impacting fragments negligible, simulating the multiple impulsive loads with single impact tests. This paper challenges this assumption, introducing the parameters of spacing, formation and timing between multiple impacts in a laboratory test method.An in house pyrotechnical triple launcher is designed and implemented which can shoot three 1.102 g Fragment Simulating Projectiles (FSP) with each shot. An add-on dispersion unit allows for adjusting the distances between the impact points. The control over the projectile velocities and the dispersion of the three impact points enables the simulation of a dense fragment cluster impact with specific characteristics. The setup is used to test Aramid dry fabrics against fragmentation. In total 53 specimens of 15 layers of Kevlar 29 plain weave fabrics are tested against single and triple impacts with two different levels of projectile dispersion. The results show a drop in the target's ballistic limit of up to 13% against triple impacts compared to single impact tests. The fabric's ballistic performance seems to improve with increasing the distances between the impact points. For every triple impact test, the parameters: impacting velocity, distances between impact points, alignment of impact points with the warp and weft directions and time intervals between impacting projectiles is documented.

Polyacrylate and Carboxylic Multi-Walled Carbon Nanotube-Strengthened Aramid Fabrics as Flexible Puncture-Resistant Composites for Anti-Stabbing Applications

Polyacrylate and Carboxylic Multi-Walled Carbon Nanotube-Strengthened Aramid Fabrics as Flexible Puncture-Resistant Composites for Anti-Stabbing Applications