Kevlar Fabric Research Articles

Impact response of Kevlar/rubber composite

This study aims to investigate the impact performance of composite panels consisting of plain-woven Kevlar fabric and rubber matrix. A finite element (FE) model in conjunction with experimental tests was developed to simulate the response of neat fabric and composite under impact loading. Each warp and weft yarn of fabric was individually modeled and combined with rubber matrix network to form the composite. To understand the effect of natural rubber on impact resistance of Kevlar/rubber composites, two types of rubber with different formulation were considered and their mechanical properties were obtained by split Hopkinson pressure bar tests and assigned to the model. Numerical results showed good agreement with the experimental data for both neat fabric and composite. It was shown that rubber matrix improves the ballistic performance of Kevlar fabric by keeping composite flexibility. High hardness rubber matrix composite has higher energy absorption capacity compared to the low hardness rubber matrix composite, due to presence of stronger intermolecular chains. Additionally, deformation and damage mechanism of fabric and composite were investigated under impact loading. The results were presented, discussed and commented upon.

Study on characterization and sorption behavior of jute reinforced epoxy composite: Hybridization effect of Kevlar fabric

This work deals with the hybridization effect of jute/Kevlar woven surface composites on water maintenance lead by organizing in different layering plans. Four different kinds of overlays were made by hand lay up procedure. Each overlay of 3 mm thickness contains different utilizes of textures and resin mix. Among them, one event is of unadulterated jute layer made for correlation sake. The surface characteristics of the jute and Kevlar fibers were depicted by Fourier Transform Infrared Spectroscopy (F.T.I.R) to analyze the compound association. The water maintenance test were performed by submerging tests into refined water. Test matrix and water maintenance are conveyed by ASTM guidelines. The present work exhibits that the hybridization of Kevlar with jute lessens the water sorption.

An Experimental Study on Impact Resistance of Different Layup Configuration of Fiber Metal Laminates

Fiber metal laminates (FMLs) are composed of thin metal sheets and fiber-reinforced composite layers. Compared to monolithic aluminum alloys, FMLs combine lower density, higher fatigue resistance, and improved damage tolerance. The present study aimed to investigate the low-velocity impact induced by drop-weight instrument and the tensile strength on various lay-up configurations of FMLs fabricated. FML samples were composed of two layers of aluminum 2024-T3 and two layers of epoxy resin, which were reinforced with carbon fabric, glass fabric, and Kevlar fabric made in pairs. In addition, another type of FMLs was developed with carbon/Kevlar fabric under the same circumstances. Force-time histories of impact forces were recorded, and the damaged specimens were inspected using optical microscopy in terms of the impact side, nonimpact side, and cross-sectional side. Experimental results indicated that the maximum impact force corresponded to the FMLs that were composed of Kevlar fabric on the impact side and glass fabric on the non-impact side. In addition, the highest tensile strength and Young’s modulus among FMLs belonged to FML with Kevlar fabric and glass fabric.

Study on the effects of Multilayered and Multi-Directional Stitched on the Ballistic performance of Kevlar fabric

Study on the effects of Multilayered and Multi-Directional Stitched on the Ballistic performance of Kevlar fabric

Lightweight Kevlar‐Reinforced Graphene Oxide Architectures with High Strength for Energy Storage

AbstractA multifunctional supercapacitor based on reduced graphene oxide (rGO) hydrogels deposited onto Kevlar fibers and woven cloth is reported, which exhibits both excellent mechanical performance and electrochemical energy storage. The specific strength of rGO hydrogel–Kevlar fibers reaches 1.6 MPa m3 kg−1 and the specific capacitance is 57 F g−1 with 38.1% of rGO. Such high specific strength is comparable to one of the as‐received Kevlar fibers (2.0 MPa m3 kg−1), indicating that the gelation process does not harm the fibers. The gel‐state symmetric device based on rGO hydrogel–Kevlar cloth survives impact from a 9.1 N force from a falling metal ball as well as deformation during bending to 90°. The high specific strength is due to the Kevlar while the specific capacitance stems from the 3D interconnected macrostructure of rGO hydrogels. To demonstrate the combination of these properties, a multifunctional efficiency is introduced based on the geometric average of mechanical and energy storage properties as compared to epoxy and carbon aerogel supercapacitor, respectively. This metric predicts an optimum combination or properties at a volume ratio of Kevlar/rGO gel between 0.0008 and 0.35.

Analysis of the transverse compressive behavior of Kevlar fibers using microscopic scale approach

During the ballistic impact process of fabrics, yarns are locally subjected to both longitudinal tensile and transverse compressive loading. This paper presents a microscopic numerical investigation of the transverse compressive behavior of a single and bulk aramid fibers. Interactions with friction between single fibers in a yarn have been taken into account. Numerical calculations were performed in the case of a transverse compression using the assumption of plane strain and validated by experimental data. Effects of friction and representative volume size were also discussed. It can be highlighted that using a numerical homogenization technique, the variation of the transverse mechanical effective property versus fiber volume fraction has been determined based on the microscopic transverse behavior of bulk aramid fibers. Finally, power relationships describing effective transverse Young's modulus E¯ and apparent strain ε¯ versus the normalized fiber volume fraction have been proposed and discussed. This effective homogenized material allows the development of homogenized Kevlar yarns and fabrics in the further works of homogenized approaches.

Mesoscale Numerical Characterization of Kevlar and Carbon–Kevlar Hybrid Plain-Woven Fabric Compression Behavior

A mesoscale finite element model (FEM) of the plain-woven fabric representative elementary volume (REV/unit cell) is developed. The developed FEM is used to predict the nonlinear compaction behavior of monolithic and intraply hybrid fabric made of high-strength carbon and Kevlar fibers. For geometrical modeling of the fabric REV, TexGen, an open-source geometrical modeling software (developed at Nottingham University), is utilized, and for mechanical characterization, FE simulation tool Abaqus® is used. Geometrical nonlinearity of the fabric, including periodic boundary conditions and yarn interactions, is incorporated in the REV FE model. Material nonlinearity caused by transversely isotropic behavior of fibrous yarns is implemented through the user material subroutine form in FE simulation along with local orientation assigned to each yarn in the REV. Material properties of fibers are extracted from the literature and supplier data. The compression behavior of monolithic Kevlar and hybrid carbon–Kevlar (carbon warp and Kevlar weft yarns, C–K) fabric is predicted using the proposed FE model. FEM-predicted results were found to have good agreement with the experimentally obtained ones. Results depict that C–K hybrid fabrics have improved compression strength. Hybridization effect is governed by yarns mutual interaction, yarn area at crossovers, and transverse in-plane properties of the interyarn hybridized fabric. The proposed FE model can be used to predict the mechanical behavior of woven fabrics with different weaving patterns, unit cell geometry, material properties, and loading conditions.

Experimental investigation of banana bract fiber and palm fiber reinforced with epoxy hybrid composites

Abstract This investigation is carried out by making a new hybrid natural composite material used Kevlar fabrics, Banana bract fibers and palm fibers. In this research, the samples prepared by hand lay method and tested for its Tensile behaviors. The fractured surfaces are analyzed by Scanning Electron Microscope (SEM). The leakages and quality of the specimen are checked by Water Absorption test. As a result, the banana bract and Kevlar composite sample shows optimum tensile strength compared to other samples and less water absorption which is useful in the application of Marine Engineering.

Hybrid approach for augmenting the impact resistance of p-aramid fabrics: grafting of ZnO nanorods and impregnation of shear thickening fluid

A novel hybrid approach has been developed and implemented to enhance the impact resistance of p-aramid fabric-based soft armour material. ZnO nanorods of diameter ca. ~ 100 nm were developed on the surface of p-aramid (Kevlar®) fabrics by seed and growth method followed by impregnation of fabrics with silica-based shear thickening fluid (STF) having 65% (w/w) concentration. The impact resistance of neat Kevlar fabric (KF), ZnO nanorod grafted Kevlar fabric (ZnO-KF), STF impregnated Kevlar fabric (STF-KF) and ZnO nanorod grafted-STF impregnated Kevlar fabric (ZnO-STF-KF) was studied. The impact energy absorption by ZnO-KF and STF-KF was higher by 29.6% and 10%, respectively, as compared to that of neat fabric (KF). The hybrid approach of modifying the Kevlar fabric with ZnO nanorods and impregnation with STF (ZnO-STF-KF) enhanced the impact energy absorption by 36.6% as compared to that of neat Kevlar fabric. The substantial increase in impact energy absorption in the case of ZnO-STF-KF can be attributed to the combined contribution of increased inter-yarn friction caused by ZnO nanorods and shear thickening behaviour of STF. The ZnO nanorod grafted high-performance fabrics impregnated with STF could be a promising candidate for the development of soft body armour material.

Effect of Continuous Micro Reinforcement and Processing Parameters on the Low-Velocity Impact Behaviour of Polymer Composite Materials

Low velocity impact tests were conducted on quasi-isotropic [�45/0/90o]xs laminates under drop weight impact from 0.7m, corresponding to a 30J energy. In this respect modified epoxy blends reinforced with carbon and Kevlar woven fabrics laminates were developed using autoclave technology. The four configurations developed for low velocity impact tests aimed at investigating several aspects like: the effect of fiber type, stacking sequence and mainly technological processing parameters, on the impact performances. The recorded Load-Time curves were plotted and visual inspection, high resolution laser scanner were used to observe the fracture characteristics of the impacted composite laminates. The results obtained showed that for tested configurations, both stacking sequence and processing parameters directly linked to fiber volume fraction, have a strong effect on the impact performances. The amount of absorbed energy, ductility index was calculated for each configuration under study. The results obtained showed that hybrid configuration exhibits lower stiffness and damage initiation energy amount when compared to carbon reinforced configurations. Nevertheless, their damage propagation energy amount and ductility index was the uppermost. This behaviour was already reported previously [1] and is partially attributed to the higher elastic energy absorption of carbon fibers that delays the propagation of delamination, and fiber breakage. Lower tenacity obtained on hybrid laminates was attributed to both lack of resin local rinse saturate and to the intrinsic anisotropy of para-aramid fibers.

Numerical Modelling of Ballistic Impact Response at Low Velocity in Aramid Fabrics.

In this study, the effect of the impact angle of a projectile during low-velocity impact on Kevlar fabrics has been investigated using a simplified numerical model. The implementation of mesoscale models is complex and usually involves long computation time, in contrast to the practical industry needs to obtain accurate results rapidly. In addition, when the simulation includes more than one layer of composite ply, the computational time increases even in the case of hybrid models. With the goal of providing useful and rapid prediction tools to the industry, a simplified model has been developed in this work. The model offers an advantage in the reduced computational time compared to a full 3D model (around a 90% faster). The proposed model has been validated against equivalent experimental and numerical results reported in the literature with acceptable deviations and accuracies for design requirements. The proposed numerical model allows the study of the influence of the geometry on the impact response of the composite. Finally, after a parametric study related to the number of layers and angle of impact, using a response surface methodology, a mechanistic model and a surface diagram have been presented in order to help with the calculation of the ballistic limit.

Anti-impact behavior of a novel soft body armor based on shear thickening gel (STG) impregnated Kevlar fabrics

A novel Kevlar/STG (Kevlar fabrics immersed with shear thickening gel) fabrics composite with high anti-impact performance was fabricated. By utilizing a unique multi-sensor force testing system, both low- and high-velocity impact experiments were conducted to investigate the anti-impact performance of Kevlar/STG fabrics. In low-velocity testing, the attenuation of the impact center force for Kevlar/STG was 64.1%, which was much larger than the Kevlar (27.0%). Under high-velocity loading, the impact force of Kevlar/STG attenuated from 805 N to 223 N with the increase of layers from 5-layers to 20-layers, while they reduced from 1125 N to 460 N for Kevlar fabrics. Meanwhile, the failure mode was analyzed and it was found that the high anti-impact performance was originated from the shear thickening effect and enhanced friction. In consideration of the good flexibility and excellent safe guarding property, the Kevlar/STG showed promising perspective in body armor.

Surface modification of Kevlar fibre fabric and its influence on the properties of Kevlar/epoxy composites

The present study addresses the enhancement of interfacial interaction between Kevlar and epoxy through surface modification of Kevlar fabric using various chemical treatments. The chemically modified aramid surface was examined by Fourier transformed infrared spectroscopy, energy dispersive spectroscopy, scanning electron microscopy (SEM), dynamic mechanical analysis and wettability characteristics. The Kevlar/epoxy composites were prepared using the hand lay-up process. Furthermore, the influence of surface modification was validated through the mechanical characteristics of Kevlar/epoxy composites. The study reveals that the chemical treatment of the Kevlar surface increases the polar functional groups and improves the interfacial adhesion between fibre and epoxy. The surface energy, work of adhesion and performance of Kevlar composites were studied for treated and untreated fibres. The tensile and flexural moduli were increased up to 38% in treated Kevlar fibre compared with untreated fibre. It was observed from SEM analysis that adhesive failure bonds rely on chemical bonds at the interface of fibre matrix composites and cohesive failure at the fibre matrix was decreased.

Effect of Electrospun Nanofiber Deposition on Thermo-physiology of Functional Clothing

The present work focuses on developing electrospun nanofibers using wire electrospinning and deposition of such nanofibrous layer on the clothing textiles. The porosity and permeability of the fabrics are substantially influenced by deposition of nanofibers on woven textiles. Cotton, Kevlar and Nomex fabrics have been selected as the substrate material. They are extensively used in the military sector for uniform of defence personnel. The emergence of nanofiber technology with the advent of needle-less electrospinning has enabled researchers to apply such materials to existing fabrics. Nylon 6 (PA6) nanofibers are spun by wire electrode spinning and deposited on selected clothing fabrics. The fabrics so developed are compared with control fabric samples for understanding the influence on thermal and physiological properties. The thermal comfort is influenced mainly by porosity and thickness of the fabric ensemble. Air permeability results are significantly influenced by nanofiber deposition. A further study on moisture management properties is also carried out. The thermal and physiological comfort is influenced mainly by porosity and thickness of the fabric ensemble. The nanofiber deposition on base fabric significantly influences water vapor and liquid water transmission related properties.

Soft body armor time-dependent back face deformation (BFD) with ballistics gel backing

This paper presents a method for obtaining time dependent back face deformation (BFD) data for body armor during ballistic impact using a clear ballistics gelatin backing and high-speed cameras to capture the deformation profile. Using this method, baseline fabric characterization data was obtained for samples comprised of varying layers of 467 g/m2 Kevlar K29 fabric impacted with 8.24 g steel ball projectile and backed with NATO standard 20% clear ballistics gelatin. For these tests, deformation depths were seen to increase with increasing impact energy and decreasing total areal density. A limited study of the various test parameters was performed by testing one additional fabric, projectile, and ballistics gelatin. From these comparisons, it was observed that 122 g/m2 Kevlar KM2+ fabric performs better per weight than 467 g/m2 Kevlar K29 fabric in terms of BFD, 9 mm FMJ projectiles produce deeper BFDs than 12.7 mm steel ball projectiles, and backing a sample with FBI standard 10% ballistics gel increases the BFD considerably over NATO standard 20% ballistics gel.

Comparative Study of Jute, E-glass and Carbon Kevlar Fabric Reinforced Polypropylene Composite

In this experiment, three types of fabric such as jute, E-glass and carbon Kevlar were selected to manufacture composites taking polypropylene (PP) as matrix material. The objective of this study is to compare the examined properties such as tensile modulus (TM), elongation at break percentage (EB %), E-Modulus (EM) of jute, E-glass and carbon Kevlar fabric reinforced polypropylene composite. The properties of manufactured composite were evaluated experimentally using computerized UTM machine according to ASTM standards. Fourier transform infrared spectroscopy was used to identify the surface groups of the composites. Water absorption and fire retardant behavior of the composites were also performed. The results revealed that the tensile strength, E-Modulus and water absorption of carbon Kevlar composite were exhibited higher than the jute and E-glass fabric reinforced composites. Different scenario has observed for elongation percentage at break. The capacity of fire retardant was noticed higher in jute fabric composite than E-glass and carbon Kevlar.

High velocity impact behavior of Kevlar/rubber and Kevlar/epoxy composites: A comparative study

This paper presents a comparison of behavior and energy absorption of neat Kevlar fabric and polymer matrix composites under high velocity impact loading. Two types of matrices including rubber and thermoset (epoxy) matrices were used in order to study the effect of a hard and brittle matrix compared with the soft and flexible matrix on energy absorption of the composite. Moreover, two types of rubber matrix with high hardness (HH) and low hardness (LH) were used in this study to investigate the effect of rubber matrix formulation on impact resistance of composites. Ballistic impact tests were performed by firing a 10 mm hemispherical projectile onto neat fabric and composites in a velocity range of 30–150 m/s for two- and four-layer samples. Results show that the matrix affects the ballistic performance of composites significantly. Rubber matrix enhances the energy absorption of the fabric by keeping composite flexibility. Increase the number of layers for Kevlar/rubber composite results in better ballistic performance. On the contrary, the thermoset matrix leads to an inflexible composite that restricts the fabric deformation and has a negative effect on the fabric’s ballistic performance. Finally, damage mechanisms were discussed in detail for each sample.

Containment of soft wall casing wrapped with Kevlar fabric

Aramid fabrics have been commonly used in the civil turbofan engine fan blade containment system for its excellent performance. To investigate the behavior and capability of soft wall containment casing, a series of fan blade released tests were conducted on the high-speed spin tester. The soft wall casing was fabricated by wrapping multiple layers of Kevlar49 plain woven fabric around a thin steel ring. Casings with different inner metal ring and outer fabric layers number were compared. The method of using the explicit dynamic software LS-DYNA to establish the finite element analysis model for the quantitative analysis of the containment process was developed and conducted. The simulation results are in good agreement with the test results. It is shown that the containment process of the soft wall casing can be divided into three impact stages. The casing with low-stiffness inner metal ring will get severe overall deformation and lose the structural integrity when it suffers the blade impact. Kevlar fabric layers will appear large bulge on outside surface and absorb the most impact dynamic energy of the high speed released fan blade. By summing up the results of the test and simulation, an empirical critical equation was derived to describe the relationship between the released blade dynamic energy and the Kevlar fabric thickness.

Effects of STF and Fiber Characteristics on Quasi-Static Stab Resistant Properties of Shear Thickening Fluid (STF)-Impregnated UHMWPE/Kevlar Composite Fabrics

In order to deeply explore the fiber characteristics influencing on stab resistance of shear thickening fluid (STF)- impregnated fabrics, two different weaving fabrics, ultra-high molecular weight polyethylene (UHMWPE) fabric and Kevlar fabrics are saturate the various concentrations and particle size of STFs. Result shows that, SiO2/PEG-200 blends demonstrate quick shear-thickening property, and the critical shear rate lowers to 1.2-45 s-1 with higher concentration of 75 nm SiO2. STF concentration and particle size significantly affect spike puncture resistance property, but the knife stab resistance mainly depends on fiber characteristics. Comparatively, STF-UHMWPE composite fabrics exhibit better knife stab resistance but weaker spike puncture resistance than STF-Kevlar fabrics. This study can provide an optimization for structure design of stab resistance armors in the future.

Comparative Study of P-aramid Based Soft and Stiff Composite Panels for Protective Application

In this research work, the authors investigated the impact behaviour of Kevlar based flexible and stiff composites. These composites were prepared by using natural rubber latex (NR) and epoxy resin respectively as matrix and p-aramid (Kevlar 129) fabric as reinforcement. For flexible composites, the ratio of reinforcement and matrix was 90:10, and for stiff composites, the ratio was 40:60. In both the cases, two layers of Kevlar fabric were used. Stitched fabric panels consisting of two layers of Kevlar were used as control. It was observed that the flexible composites exhibited 2.8 times higher puncture force whereas for stiff composites the value was 6.6 times in comparison to only stitched panels. In terms of impact energy absorption, flexible composites showed 73 % higher value as compared to the stitched panels whereas for stiff composites, 86 % reduction was witnessed.