Kevlar Fabric Research Articles

Mechanical behavior of the polyamide 6.6 nanofiber and MWCNT‐reinforced hybrid nanocomposites

AbstractThe present study examines the influence of polyamide 6.6 (PA 6.6) nanofiber and MWCNTs reinforcements on the mechanical behavior of nanocomposite plates formed by hybridization of carbon fabric (CF) and kevlar fabric (KF). First, PA 6.6 nanofibers were manufactured by electrospinning. The produced nanofibers were placed in the interlaminar of nanocomposite plates. PA 6.6 nanofiber and MWCNT‐reinforced nanocomposite plates consisting of 12 layers were produced by the vacuum bagging method. Tensile, Mode‐II fracture and bending tests were applied to the produced composite plates in accordance with the standards. After the mechanical tests, the nanocomposite plates' macro and micro damage analysis was performed. As a result of the reinforcement of PA 6.6, MWCNTs and PA 6.6‐MWCNTs, the tensile strength, interlaminar fracture toughness and bending strength of the nanocomposite plates significantly enhanced compared to unreinforced samples. In addition, interlaminar crack propagation in reinforced samples became more stable than in the unreinforced sample.Highlights Investigated the impact of PA 6.6 nanofiber and MWCNT reinforcements on nanocomposite plates formed through CF and KF hybridization. Reinforcement with PA 6.6, MWCNTs, and PA 6.6‐MWCNTs significantly improved tensile strength, interlaminar fracture toughness, and bending strength. Mode‐II interlaminar fracture toughness tests demonstrated enhanced crack propagation stability with PA 6.6 nanofiber and MWCNT reinforcements.

Characteristics of Carbon and Kevlar Fibres, Their Composites and Structural Applications in Civil Engineering-A Review.

Kevlar and carbon fibres and fabrics have won a leading place in the structure market, although such materials are not cheap, and are increasingly used for reinforcing and strengthening structural elements in the civil engineering, automotive, aerospace and military industries, due to their superior mechanical properties, especially in terms of strength. The mechanical characteristics of such composite materials must be known in order to numerically simulate the mechanical behaviour of such structures in terms of the distribution of stresses and strains. It has also become a necessity to understand the effects of reinforcement with both types of fibres (carbon fibres and Kevlar fibres) on the mechanical properties, especially on the impact properties of such composites. This review aims to expose the main advantages and disadvantages of the hybridization of carbon and Kevlar fibres. For this reason, an overview is presented concerning the main characteristics (tensile strength, flexural strength, impact strength, coefficient of thermal expansion and so on) for carbon and Kevlar fibres and also for hybrid Kevlar-carbon composite materials to aid in the design of such hybrid composite materials. Finally, some civil construction rehabilitation and consolidation applications of the composites reinforced with carbon fibre, Kevlar fibre or with hybrid Kevlar-carbon fabrics are highlighted in the last part of the paper.

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.

Experimental investigation on low-velocity impact behavior of glass, Kevlar, and hybrid composites with an elastomeric polyurethane matrix

Low-velocity impacts represent a critical dynamic condition for engineering structures. Combining two reinforcing fibers in a single matrix, i.e., hybridization, is considered a feasible way to improve composite performance. In this context, this paper presents an experimental work on composites with Kevlar and glass fabrics and a novel thermoset polyurethane matrix. The coupons are manufactured by vacuum infusion technique and low-velocity impact tests are carried out. First, the impact behavior of Kevlar and glass laminates of different thicknesses is assessed, and then impact tests are performed on different configurations of hybrid laminates, both symmetric and non-symmetric. For the non-symmetric specimens, impact tests were conducted on both sides of the stack. Load vs displacement curves are reported along with absorbed energy. To investigate the damage mechanism, the front, back, and cross-section views of the specimens are analyzed, and features related to the stacking sequences are discussed. Thermographic analyses are carried out on the impacted specimens to further analyze damage. The failure mechanisms are different from traditional epoxy composites and a hybridization effect is reported. The results evidence that the hybrid coupons are viable for structural applications, being capable of absorbing high-impact energies, in particular, non-symmetric hybrid laminates outperformed the Kevlar, glass, and symmetric ones, absorbing roughly 15% less energy for the highest energy impact.

Preparation and characterization of shear thickening fluid/carbon nanotubes/Kevlar composite materials

AbstractShear thickening fluid (STF), carbon nanotubes (CNTs) are both promising in body protection and anti‐impact for the drastic viscosity change of STF and the extremely high tensile strength and elongation of CNTs. The excellent performance of the above two combined with traditional Kevlar fabrics can significantly improve the mechanical properties and reduce the number of layers used for body protection. This work reports a new method to prepare STF/CNTs/Kevlar with excellent tensile properties and anti‐impact performance by spraying method with 1 wt% polyvinyl alcohol (PVA) solution as a binder for better integration between CNTs and Kevlar. Surface morphology changes in the preparation process indicate the combined structure of PVA binder, CNTs, and STF, presenting a uniform macroscopic and nonuniform microscopic surface of STF/CNTs/Kevlar composite. The tensile strength and anti‐impact properties including punch residual velocity and energy absorbed were studied and results for STF/CNTs/Kevlar composite are 669.8 ± 18.1 MPa, 1.602 ± 0.045 m/s, and 21.683 ± 1.182 J in 12 ms, increased by 46.4%, 23.0%, and 240.2%, respectively, compared with neat Kevlar, owing to the improved tight bonding and friction between fabrics yarns caused by PVA adhesive and tangled CNTs, accompanied with the enhanced viscosity of STF under forces.Highlights Composites were made by spraying PVA, CNTs, and STF onto Kevlar fabrics; The tensile strength of the composite was 46.4% higher than Kevlar; The energy absorbed in 12 ms in anti‐impact tests was improved by 240.2%; Tight bonding and friction between yarns are reasons to improve properties; The raised viscosity of STF under forces is useful for mechanical properties.

Investigation of stresses in a Kevlar (491PR-286) material disc by the Chebyshev pseudospectral method

In this study, a composite disc with Kevlar (491PR-286) material was modeled. Kevlar consists of very strong fibers of very light carbon origin. That is why they are used quite often in unmanned aerial vehicles and spacecraft. The disc has been subjected to thermal stress under a linearly increasing temperature distribution. The temperature limit conditions were applied as 25 °C, 50 °C, 75 °C, 100 °C, and 150 °C. The obtained findings were determined using a computer program, the psedudospectral Chebyshev method, and analytically in three different ways. The main difference between this study and other studies is that it investigates the thermal stresses occurring in circular discs using different methods. The results obtained are compared fairly among themselves and presented with graphs. It was determined that tangential stresses were higher than radial stresses at the studied temperature values. In the analytical study conducted, the radial stresses on the inner and outer surfaces of the disc were determined to be zero for the boundary conditions. Under the increasing temperature distribution from the inner surface to the outer surface, tangential stresses occurred as tensile stress on the inner part of the disc and compressive stress on the outer part. Under the decreasing temperature distribution from the inner surface to the outer surface, tangential stresses are pressed on the inner part of the disc, resulting in a tensile stress on the outer part. It is observed that with increasing temperature, there is an increase in radial and tangential stress values. At the end of the study, it was concluded that Kevlar (491PR-286) material discs can be used at high temperatures.

ANALISIS UJI EDX PADA MATERIAL BERPENGUAT KARBON KEVLAR DENGAN METODE VACUUM INFUSION DAN VACUUM BAGGING

This study aims to determine the comparison of specific characteristics of bending testing of carbon fiber kevlar material made using two manufacturing methods, namely the vacuum infusion manufacturing method and the vacuum bagging manufacturing method which is then continued with EDX (Energy Dispersive X-Ray) testing to determine the elements contained in the specimen. The results of the analysis of the average bending test results show that the specimen with the vacuum infusion manufacturing method is the method with the best results compared to the vacuum bagging manufacturing method, indicated by the average result of 253.68 MPa for the vacuum infusion method, while for the vacuum bagging method it is shown with an average result of 187.87 MPa. The EDX test results show that the micro-composition of specimens with the vacuum infusion method has a content of O2 and N of 16.83% so that it has a better density because it contains few voids, while for specimens with the vacuum bagging method has a content of O2 and N of 49.78% so that it has a less good density because it contains more voids

Manufacturing Scalable Carbon Nanotube-Silicone/Kevlar Fabrics.

Carbon nanotube (CNT) hybrid composites were formed by combining a CNT and silicone elastomer solution with Kevlar yarn, Kevlar fabric, and Kevlar veil materials. The integration of a CNT-silicone matrix with Kevlar yarn and fabric materials produced a composite with moderate electrical and thermal conductivity due to CNT fabric combined with the strength of Kevlar fabric or yarn. In the material synthesis, a notable difficulty was that the CNT-silicone did not bond strongly to the Kevlar. The composites passed the Vertical Flame Test ASTM D6413 and the Forced Air Oven Test NFPA 1971. These hybrid composites can have multiple applications in areas requiring favorable conductivity, strength, and flame and heat resistance. The application areas include firefighter apparel, military equipment, conductive/smart structures, and flexible electronics. The synthesis process used to manufacture CNT-silicone/Kevlar composites yielded composite sheets with an area of 2250 cm2. The process is scalable and customizable for the synthesis of CNT composites with tailored properties. Improvements in the bonding of CNT-silicone to Kevlar are being investigated.

Optimum carbonization of Kevlar fabric for electromagnetic interference shielding applications

The study involved single-stage carbonization and physical activation of Kevlar woven fabric to convert into activated carbon fabric. The carbonization process was optimised for high carbon yield and low electrical resistivity of activated carbon fabric using Box-Behnken experimental design and response surface methodology. The three process parameters namely charcoal amount, gas flow rate, and carbonization temperature were selected. The empirical equations obtained through response surface methodology for carbon yield and electrical resistivity were found in good agreement with the experimental values. An optimum amount of charcoal, optimum nitrogen flowrate, and low carbonization temperature was found suitable for higher carbon yield. On the other hand, high charcoal amount, high carbonization temperature, and optimum nitrogen flow rate resulted in low electrical resistivity of activated carbon fabric. Later, the activated carbon fabrics were prepared under the optimum carbonization conditions to get high carbon yield and low electrical resistivity. The optimized sample for electrical resistivity showed higher electromagnetic interference (EMI) shielding properties at lower as well as higher frequencies due to its highly porous morphology and electrical conductivity.

Shock wave mitigation and impact resistance response of kevlar fabric with novel shear-stiffening gel core

A novel shear thickening gel with micro-scale hard/soft interface structure and low reaction temperature was proposed in this article. The gel was named TH and used as core material within Kevlar fabrics. Storage modulus of TH was proved to increase by around two orders with increasing of shear frequency, and dynamic properties indicated that TH could dissipate or store more energy. TH can adhere with Kevlar fabrics well and satisfactorily fulfill the gap between fabrics. As a result, shock wave peak pressure and positive impulse decreased markedly. Wavelet decomposition analysis show that high frequency energy was filtered by protection materials. Meanwhile, impact resistance test suggested the existence of TH changed the stress propagation routes and avoided pulling out for Kevlar fabrics. Samples filled with TH demonstrated a better shock wave mitigation ability and impact resistance. Energy dissipation structures with TH have a promising prospect in the application of defending area.

Covalently modified Kevlar fabric incorporating graphene oxide with enhanced antibacterial properties and preserved strength.

This work describes a multi-step modification process for the covalent transformation of Kevlar fabric en route the incorporation of graphene oxide (GO) nanosheets. Spectroscopic, thermal and microscopy imgaing techniques have been employed to follow step-by-step the modification of Kevlar and the formation of the corresponding Kevlar-GO hybrid fabric. The level of Kevlar's functionalization can be controled with the nitration time, the first reactionin the multi-sequence organic transformations, for obtaining the hybrid fabricwith a content of GO up to 30%. Most importantly, the covalent post-modification of Kevlar does not occur in the expense of the other otherwise excellent mechanical properties of the fabric. Under optimal conditions, theKevlar-GO hybrid fabric shows a 20% enhancement of the ultimate strengh. Notably, when the Kevlar-GO hybrid fabric exposed to cyanobacterialSynechococcusthe bacteria growth was fully inhibited. Overall, the covalently modified fabric demonstrated significant antibacterial behavior, excellent strength and stability under common processes. Due to its simplicity, the methodology presented in this work not only promises to result in a standard procedure to functionalize themerunits of Kevlar witha variety of chemicals and nanomaterials but it can be also extended for the modification and hybridization of other fabrics.

Investigating the effect of external force on the collision of an iron bullet with shear-thickening fluid nanocomposites using molecular dynamics simulation

The main uses of bullets are as projectiles in firearms for military, law enforcement, and civilian purposes. However, bullets have significant industrial applications beyond their role in weaponry, such as precision drilling, cutting, and shaping of hard materials. Steel bullets have a very resistant structure and will not be damaged if exposed to corrosion. Other applications that are resistant to strike and projectiles, such as the automotive and aerospace industries, are based on fibers or fabrics with high toughness and tensile strength, such as Kevlar and p -aramid fibers, which are impregnated with some thermoplastic or thermoset polymers. Therefore, in the upcoming research, the impact of external force (EF) with various values (0.1, 0.2, 0.3, 0.4, and 0.5 V/Å) on the strength of Kevlar nanofibers reinforced with silicon dioxide (SiO2) nanoparticles and ethylene glycol (EG) has been investigated using LAMMPS software. EG and SiO2 nanoparticles with 10 and 2 vol% were added to Kevlar fabrics, creating a shear thickening fluid (STF) nanocomposite. The energy parameters of the interaction between the particles, collision velocity, and the center of mass have been calculated. The findings of the research indicate an increase in the interaction energy from 111271.85 to 154351.15 kcal/mol, an increase in the collision velocity from 0.7046 to 1.5812 Å/fs and an increase in the center of mass from 0.62671 to 1.1670 Å due to the EF applied from 0.2 to 0.4 (kcal/mol)/Å. These results show EF should be optimized in actual cases for the collision process to occur effectively.

Physico‐mechanical, and thermal properties of sisal/hemp/Kevlar fibers, fly ash and Titanium Carbide nanoparticles reinforced bioepoxy composites

AbstractIn the present investigation, the chemically treated and untreated sisal/hemp fibers, fly ash or titanium carbide (TiC) nanofillers, and Kevlar fabrics reinforced bio epoxy (Sr 56) polymer matrix were manufactured using the wet layup method. Experimentation was performed to study the physical, mechanical and thermal properties. This investigation also includes determining the influence of accelerated weathering on the specimen surface for 5 months. The tensile fracture of the sample before and after the accelerated weathering from scanning electron microscope (SEM) pictures exhibited that the extensive failure principles in the laminates in terms of matrix cracking, fiber breakage, delamination, and fiber pull out. The thermal analysis examined the onset, endset temperature, transition loss, and carbon residue which were also reduced after the accelerated weathering. It exhibits that adding fly ash or TiC nanoparticles as an altered inhibitor against the weathering in the bio epoxy hybrid composite scheme can reduce the undesirable impacts from moisture and Ultra‐violet light exposure.Highlights Sisal/hemp fibers were chemically treated to reduce hydrophilicity. Contact angle of KSCHCTBE56 improved to 84.04°. SEM confirmed uniform dispersion of fillers and enhance mechanical strength. Mechanical and thermal characteristics reduced after accelerated weathering.

Impact Performance of Kevlar Fabrics with Shear Thickening Fluid

In modern day warfare, flexible and light weight body armor, which can provide protection to all the parts of body against all kinds of shrapnel and bullets, is required. The best suited material for its application is Kevlar based bullet proof vest and wearable. However situation requires lesser number of Kevlar layers to make the protective layer which will be extremely light and provide flexibility of motion. To achieve this, a non-Newtonian fluid known as Shear Thickening Fluid (STF) is developed, optimum value is obtained for Kevlar-STF combination and the layers of Kevlar are impregnated with STF. Samples of 4, 6 and 8 layers of Kevlar fabrics are bonded together at the edges by epoxy resin and are subjected to impact loading for different speeds. Experiments are conducted till the ballistic limits of the samples and the ballistic limit values are obtained. The energy absorbed, residual velocities and the ballistic limits of the sample are calculated and compared with theoretically calculated values. Experiments are carried for fabrics with and without STF. It is found that there is a substantial increase in the energy absorption of Kevlar with the addition of STF and the study reveals that the STF based impact resistant structures can be better structural armor material with less number of layers and less weight

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.

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.

Enhancing the quasi-static strength of prosthetic socket made from composite laminates via hybridisation: Experimental and numerical study

This study aims to develop composite laminates for the manufacture of prosthesis socket with enhanced mechanical performance. Layered hybridisation of fabrics (i.e. glass, carbon, and Kevlar fabrics) is used to manufacture hybrid composite laminates by resin infusion via vacuum bagging method. The response of these materials to compression loading is investigated by using compression-loading testes and the load-bearing ability was examined by tensile strength tests. Moreover, finite element analysis has been carried out by using the Abaqus software to predict the compressive failure load and damage failure modes for all sockets samples. Experimental results revealed that the hybrid laminates exhibited more stability and higher absorbing energy compared to non-hybrid laminates during compressive loading tests. Furthermore, the hybridisation of fabrics layers can play key role for improving the tensile strength properties of hybrid composite laminates compared to composite laminates without hybridisation. The numerical simulation results of compressive failure load and damage failure modes are in accordance with experimental results qualitatively as well as quantitatively.

Surface modification of kevlar fabric with a novel sulfonyl aryl containing monomer and its influence on inter yarn friction

The ballistic impact response of Kevlar textiles is significantly influenced by the friction between the yarns. It increases the dissipation of energy when yarns begin to displace relative to one another and it also results in to transfer of load to a larger area during ballistic impacts. In the present work, a novel sulfonyl aryl group containing monomer acrylic acid-2-(toluene sulphonyl amine)-ethyl ester (AATSAEE) was synthesized by a three-step process with ethanol amine and p-toluene sulfonic acid as starting material. The monomer was homopolymerized and grafted on Kevlar fabric by UV-induced free radical polymerization technique. Benzoyl peroxide (BPO) was used as initiator. Utilizing spectroscopic and thermal gravimetric methods, the monomer, precursor, and the homopolymer were characterized. The yarn pull-out tests on unmodified and AATSAEE grafted Kevlar fabrics were performed on Universal Tensile Tester at a steady speed of the upper jaw of 50 cm min−1. Increases in yarn pull out force have been noted with grafting of AATSAEE on Kevlar fabric. The peak force increases around 284% with grafting which indicates an increase in friction forces. When these yarns start to move apart from one another due to friction factors, the fabric’s energy dissipation increases and it may results in to increase in energy absorption at the time of ballistic impacts.

Effects of ZnO nanowire and silica coatings on the inter-yarn friction and ballistic properties of Kevlar fabrics

This paper focused on improving the ballistic performance of plain weave (PW) and twill weave (TW) Kevlar fabrics without affecting the weight. Single layers of fabrics were subjected to two different surface coatings, one with ZnO nanowires (ZnO NW) and other with Silica nanoparticles. Tensile, inter-yarn friction and ballistic properties of bare and surface coated fabrics were evaluated and compared with each other. All types of PW fabrics were found to have superior tensile strain energy, inter-yarn friction and ballistic energy absorption than corresponding TW fabrics. Both ZnO NW and Silica coatings were found to significantly improve the strain energy, inter-yarn friction and ballistic energy absorption of fabrics with only less than 8% increase in the areal density of the fabrics. Among the two surface treatments, Silica coating was found to provide maximum improvement in properties. It increased the strain energy, yarn pull-out energy and ballistic energy absorption in PW fabrics by 67%, 694% and at least 240%, respectively. Also, it increased the strain energy, yarn pull-out energy and ballistic energy absorption in TW fabrics by 42%, 1350% and 387%, respectively. The work demonstrated promising ways of improving the ballistic performance of Kevlar fabrics.

Comparative Investigations on Fracture Toughness and Damping Response of Fabric Reinforced Epoxy Composites

Studies were conducted to observe the effect of fracture toughness and damping response on fabric reinforced epoxy polymer composites. The samples of glass fabric, kevlar fabric and carbon fabric having 15wt%, 25wt%, 35wt%, 45wt% and 55wt % fabric content were prepared and tested following ASTM standards. Fracture toughness, peak load and increase in energy absorption are determined for the fabric-epoxy composites. Effect of temperature on storage modulus, loss modulus and tan delta values for various percentages of fabric epoxy composites are noticed and corresponding damping response behaviour is determined. The results revealed that reduction in strength at higher percentage of fabric content is due to improper bonding between fabric and epoxy resin. Higher peak load values and increased values of energy absorption are observed at lower percentage of fabric content. Kevlar fabric proves to be beneficial for specific energy absorption capability. Strength retention capability at higher temperature is far better for carbon fabric epoxy combinations. Composites with lower fabric content retain much higher temperature and peak load. Also the experimental findings are in close proximity with that of theoretical results.