Showing papers on "Kevlar published in 2015"

Evaluation of the mechanical behavior of epoxy composite reinforced with Kevlar plain fabric and glass/Kevlar hybrid fabric

Abstract: In this study, composite plates were manufactured by hand lay-up process with epoxy matrix (DGEBA) reinforced with Kevlar fiber plain fabric and Kevlar/glass hybrid fabric, using to an innovative architecture. Results of the mechanical properties of composites were obtained by tensile, bending and impact tests. These tests were performed in the parallel direction or fill directions of the warp and in a 90° direction. FTIR was used in order to verify the minimum curing time of the resin to perform the mechanical tests, and scanning electron microscopy was used to observe reinforcement and matrix fractures. Composites with Kevlar/glass hybrid structure in the reinforcing fabric showed the better results with respect to specific mechanical strength, as well as bending and impact energy.

Effects of Kenaf Contents and Fiber Orientation on Physical, Mechanical, and Morphological Properties of Hybrid Laminated Composites for Vehicle Spall Liners

Abstract: The aim of this work is to study the effect of kenaf volume content and fiber orientation on tensile and flexural properties of kenaf/Kevlar hybrid composites. Hybrid composites were prepared by laminating aramid fabric (Kevlar 29) with kenaf in three orientations (woven, 0o/90o cross ply uni-directional (UD), and non-woven mat) with different kenaf fiber loadings from 15 to 20% and total fiber loading (Kenaf and Kevlar) of 27–49%. The void content varies between 11.5–37.7% to laminate with UD and non-woven mat, respectively. The void content in a woven kenaf structure is 16.2%. Tensile and flexural properties of kenaf/Kevlar hybrid composites were evaluated. Results indicate that UD kenaf fibers reinforced composites display better tensile and flexural properties as compared to woven and non-woven mat reinforced hybrid composites. It is also noticed that increasing volume fraction of kenaf fiber in hybrid composites reduces tensile and flexural properties. Tensile fracture of hybrid composites was morphologically analysed by scanning electron microscopy (SEM). SEM micrographs of Kevlar composite failed in two major modes; fiber fracture by the typical splitting process along with, extensive longitudinal matrix and interfacial shear fracture. UD kenaf structure observed a good interlayer bonding and low matrix cracking/debonding. Damage in composite with woven kenaf shows weak kenaf-matrix bonding. Composite with kenaf mat contains the high void in laminates and poor interfacial bonding. These results motivate us to further study the potential of using kenaf in woven and UD structure in hybrid composites to improve the ballistic application, for example, vehicle spall-liner. POLYM. COMPOS., 36:1469–1476, 2015. © 2014 Society of Plastics Engineers

Effect of a carbon nanotube coating on friction and impact performance of Kevlar

Abstract: Because surface treatments of high-performance fibers have previously resulted in increased friction and improved impact performance, it was of interest to evaluate the influence of multi-walled carbon nanotubes (MWNTs) on impact performance and contributing constituent properties of Kevlar. Kevlar K129 yarns and fabrics were modified via sonication in a solution of N-methylpyrrolidone (NMP) and MWNTs. This method has the potential to both improve the intrinsic properties of the fibers themselves as well as increase the friction, with very low mass addition. Tensile, static friction, and pull-out tests were performed to compare the properties of MWNT-treated materials to neat. As a result of MWNT augmentation, yarn modulus increased up to 15 %, and static and kinetic friction coefficients increased up to 30 %. Yarn pull-out tests revealed up to a 230 % increase in the forces required to pull-out yarns. To study the effects of MWNT augmentation on dynamic performance, low-velocity impact tests of steel spheres on a single ply of fabric were performed. These experiments demonstrated approximately 50 % increase in ballistic limit for MWNT-treated Kevlar with negligible (0.4–1.4 %) increase in mass. Entanglement among MWNTs along with increased surface roughness and surface area increased the resistance to motion, improving impact performance by increasing the energy required to pull-out yarns from the textile, while inhibiting textile windowing and driving a larger number of yarn failures. The observed changes in fabric response suggest that MWNT treatments have the potential to improve the ballistic limit of fabrics through increased interfilament and interyarn friction without compromising fiber strength or adding significant mass.

A Review on Natural Fiber Reinforced Polymer Composites

Abstract: FRP's have huge applications in the field of Automobile, Aerospace, Military applications, Building and Construction Industries (ceiling, paneling and partition boards) Etc. These applications are due to its low weight and high mechanical properties. Fiber Reinforced Polymer composite have a very dominant role in variety of applications for their high specific strength and modulus. Lot of work is carried by various researches with different reinforcements. The reinforcement used in various applications are Fibers of Glass, Carbon, Aramid, Asbestos and Kevlar fibers. Since the natural reinforcements have less side effect and abduantly available, Lot of researches reviewed with natural reinforcements for various applications in the form of sheets, boards etc. Due to the limitations of synthetic fibers as reinforcement the use of FRP composite increased the interest of researches. The mechanical properties of a natural fiber reinforced composite depend on parameters like fiber strength, fiber length, chemical treatment and orientation in addition to fiber-matrix interfacial bond strength. Here this review article is taken as natural fiber reinforcement for development of composites.

Tailored interyarn friction in aramid fabrics through morphology control of surface grown ZnO nanowires

Abstract: Para-aramid fibers, such as Kevlar, have been the most common material used for ballistic applications by providing a variety of energy absorption mechanisms to dissipate a projectile’s momentum. One important mechanism is interyarn friction, which can be controlled through surface treatment of the fibers. It was recently shown that the growth of ZnO nanowires on the surface of the fibers could increase the interyarn friction, producing 10.85 times higher peak load and 22.70 times higher energy absorption compared to neat fabrics. Here, it is demonstrated that variation of the morphology of the nanowires produces a drastic change in the pullout behavior with low aspect ratio nanowires producing the largest increase in pullout force. While weight of the modified fabrics increased only 20% compared to the bare ones, tensile test results show that the growth of ZnO nanowires enhances both tensile strength and elastic modulus of the fabrics by 13% and 10%, respectively. A comprehensive post-test micrograph analysis is performed to reveal possible enhancement mechanisms of modified aramid fabrics with different nanowire morphologies.

Computational Investigation of High Velocity Ballistic Impact Test on Kevlar 149

Abstract: The Kevlar is an organic high crystalline fiber belonging to the aromatic polyamide family extensively used for its strength. Kevlar fiber posses high cut resistance and flame resistance, hence they have a wide range of application in ballistic and defense [2]. This paper investigates how K-149 behaves mechanically under sudden high velocity impact, it also shows which types of Kevlar grade hold the maximum impact stiffness capacity. In addition it also predicts the stress induced on the specimen at the time of impact. The ballistic impact object considered as 9mm standard size bullet used in short gun. The assumed velocity for these cases is 650m/s. The specimens K-149 & k-49 taken to be rectangle with the standard size 50 mm x 50 mm. The computational analysis done on Kevlar 49 & 149 and the results have been compared with the help of the pictorial representation of post processing abaqus results and the best ballistic material can be chosen. This paper also provided the recommended research data to fill the technology gap in defense material science.

Strain-dependent dynamic mechanical properties of Kevlar to failure: Structural correlations and comparisons to other polymers

Abstract: The processing of Kevlar to certain strengths by hot-drawing can benefit by quantitative understanding of the correlation between structural and mechanical properties during the pre-drawing process. Here, we use a novel continuous dynamic analysis (CDA) to monitor the evolution in storage modulus and loss factor of Kevlar 49 fibers as a function of strain via a quasi-static tensile test. Unlike traditional dynamic mechanical analysis, CDA allows the tracking of strain-dependent mechanical properties until failure. The obtained dynamic viscoelastic properties of Kevlar 49 are correlated with structural data obtained from synchrotron radiation analysis and with Raman scattering frequencies. Rate-dependent stress–strain results from Kevlar are compared to Nomex, spider silk, polyester and rubber, and provide insight into how the mechanical properties of Kevlar originate from its characteristic structural features. We find that as the storage modulus of Kevlar is essentially equal to the Young's modulus, the measured quantitative relationships between storage modulus and strain can provide insights into the tuning of the mechanical properties of aramid materials for specific applications.

Determination of Fracture Behavior under Biaxial Loading of Kevlar 149

Abstract: The high crystalline fiber Kevlar 149 has a major industrial application and it is extensively used in aerospace industries due to its significant properties of ultra-high modulus, high strength, low density, high flame resistance. Kevlar 149 has an advantage over K 49, since it absorbs less moisture and has high compression strength [3]. In order to explore the vast application, this paper investigates the fracture response of the Kevlar material computationally, when they are subjected to biaxial loading in both tensile and compression. This loading is done to understand the response of the Kevlar how far they poor in compression and rich in tensile. The fiber induced with epoxy is to form as an effective reinforcement. Here the fiber taken as Kevlar 149 & K-49 and the epoxy resin. For easy understanding a sample of two flat plates is considered as a composite structure of standard size, which under goes the biaxial loading computationally using Abaqus/CAE. The pictorial data’s are taken from the post processing study and the data’s can be used to investigate the fracture mechanism of Kevlar 149 & K-49, under different types of strain loading. The output results of Kevlar 149 is compared with K-49 to analyze the behavior of fiber undergoes the biaxial loading both compressive and tensile and also the merits and effective utilization of K-149. It is suggested that this method can be applied to other type of composite materials.

Sound Absorbent, Flame Retardant Warp Knitting Spacer Fabrics: Manufacturing Techniques and Characterization Evaluations

Abstract: This study proposes a combination for reciprocal reinforcement between warp knitting spacer fabrics and PU foams. PET/Kevlar nonwoven fabrics are made with an 80:20 ratio and an incorporation of various needle-punching speed of 100, 150, 200, 250, and 300 needles/min. Ascribing to having an optimal bursting strength, sound absorption coefficient, and limited oxygen index (LOI), the PET/Kevlar nonwoven fabric that is made by 200 needles/min are selected to be combined with a glass-fiber fabric by applying needle punch in order to form a surface layer. Next, warp knitting spacer fabrics and the nonwoven fabrics are laminated, followed by being combined with polyurethane (PU) foam that are featured with different densities of 200, 210, 220, 230, and 240 kg/m3 in order to form spacer fabric/PU foam composites with multiple functions. The composites are then tested with a drop-weight test, a compression test, a bursting strength test, a sound absorption test, and a horizontal burning test. The test results indicate that all spacer fabric/PU foam composites reach a horizontal burning level of HF1, and their sound absorption coefficients at 2500-4000 Hz also suggest a satisfactory sound absorption. In particular, the optimal residual stress and compressive strength are present when the composites contain 210 kg/m3 PU foam. Similarly, the optimal bursting strength of the composites occurs when they are composed of 230 kg/m3 PU foam. The spacer fabric/PU foam composites are proven to have high strengths, sound absorption, and fire retardant, and thus have promising potentials for use as construction materials and light weight composite planks.

Impact resistance properties of kevlar/glass fiber hybrid composite laminates

Abstract: In this paper, the impact behavior of Kevlar/glass fiber hybrid composite laminates was investigated by performing the drop weight impact test (ASTM D7136). Composite laminates were fabricated using vacuum bagging process with an epoxy matrix reinforced with twill Kevlar woven fiber and plain glass woven fiber. Four different types of composite laminates with different ratios of Kevlar to glass fiber (0:100, 20:80, 50:50 and 100:0) were manufactured. The effect of Kevlar/glass fiber content on the impact damage behavior was studied at 43J nominal impact energy. Results indicated that hybridization of Kevlar fiber to glass fiber improved the load carrying capability, energy absorbed and damage degree of composite laminates with a slight reduction in deflection. These results were further supported through the damage pattern analysis, depth of penetration and X-ray evaluation tests. Based on literature work, studies that have been done to investigate the impact behaviour of woven Kevlar/glass fiber hybrid composite laminates are very limited. Therefore, this research concentrates on the effect of Kevlar on the impact resistance properties of woven glass fibre reinforced polymer composites.

Fabrication, polarization, and characterization of PVDF matrix composites for integrated structural load sensing

Abstract: The focus of this work is to evaluate a new carbon fiber reinforced composite structure with integrated sensing capabilities. In this composite structure, the typical matrix material used for carbon fiber reinforced composites is replaced with the thermoplastic polyvinylidene difluoride (PVDF). Since PVDF has piezoelectric properties, it enables the structure to be used for integrated load sensing. In addition, the electrical conductivity property of the carbon fabric is harnessed to form the electrodes of the integrated sensor. In order to prevent the carbon fiber electrodes from shorting to each other, a thin Kevlar fabric layer is placed between the two carbon fiber electrode layers as a dielectric. The optimal polarization parameters were determined using a design of experiments approach. Once polarized, the samples were then used in compression and tensile tests to determine the effective d33 and d31 piezoelectric coefficients. The degree of polarization of the PVDF material was determined by relating the effective d33 coefficient of the composite to the achieved d33 of the PVDF component of the composite using a closed form expression. Using this approach, it was shown that optimal polarization of the composite material results in a PVDF component d33 of 3.2 pC N−1. Moreover, the Young's modulus of the composite structure has been characterized.

Investigation of Fatigue and Compression Strength for the PMMA Reinforced by Different System for Denture Applications

Abstract: In the present search, attempts are made to develop the properties of PMMA resin that used for upper and lower prosthesis complete denture, by addition two different types of particles, which included: nano-hydroxyapatite (nHA) particles and micro-zirconia (ZrO2) particles that added with different volume fractions of (1%, 2% and 3%) to poly methyl methacrylate (PMMA) cold cured resin as new fluid resin as a matrix. Also woven glass fiber kind (E-glass) and woven Kevlar fiber kind (49), it were added with a fixed volume fraction of (5%) to PMMA composites. In this work the composite prosthetic dentures specimens preparation was done by using (Hand Lay-Up) method as six groups which includes: the first group consists of PMMA resin reinforced by nHA particles, the second group consists of PMMA resin reinforced by ZrO2 particles, the third group consists of (PMMA-nHA) and glass fiber layer as laminated composite , the fourth group consists of (PMMA-ZrO2) and glass fiber layer, the fifth group consists of (PMMA-nHA) and Kevlar fiber layer and the sixth group consists of (PMMA-ZrO2) and Kevlar fiber layer. The compression test result shows that the values of compression strength increased with increasing the volume fraction of (nHA and ZrO2) particles for all groups’ specimens. And the results showed the (PMMA-ZrO2) composite has greater values for compression strength. As well as the results shows that the maximum value of compression strength for hybrid laminated composite is obtained in hybrid laminated composite materials for fourth groups’ specimens (PMMA-ZrO2-5% Glass Fiber). Whereas the values of fatigue strength of hybrid laminated composite (PMMA-5% Kevlar fiber-3% nHA), it was higher than the fatigue strength of hybrid laminated composite (PMMA-5% Glass fiber-3% nHA) and the base material (Pure PMMA). The fatigue strength values at (106) loading Cycle for these specimens were (52, 38 and 15 MPa) respectively.

Optimization of interlaminar shear strength behavior of anodized and unanodized ARALL composites fabricated through VARTM process

Abstract: Aramid Aluminum laminates (ARALLs), which belong to the family of fiber metal laminates (FML’s) are prone to interlaminar shearing because of weak bonding between Aluminium and Kevlar layers. Moreover standard fabrication procedure of these composites is to use unidirectional fiber prepregs with Aluminium alloy sheets. The fabrication thus involves expensive semi prepared materials (prepregs) followed by autoclaving. Over the recent years VARTM (Vacuum assisted resin transfer molding) has emerged as a viable and low cost technique for composites fabrication. In this paper an alternative fabrication procedure for ARALL composites using VARTM has been presented. For this purpose Aluminium 2024 T3 alloy and plain woven Para-Aramid (Kevlar 49 from DuPont) fibrous tow sheets were used to make ARALL composites. ARALL comprises of one sheet of Kevlar in the center and two layers of Aluminum on its two sides. Two types of Aluminium sheets were prepared i.e., anodized and unanodized. Specimens were prepared using VARTM technology. Two types of post curing treatments were chosen. One group of specimens was post cured at 100 °C while the other group was left to cure at room temperature. T-peel tests were then conducted using ASTM D1876 standard on ARALL specimens thus prepared. This research study entails anodization and curing/post curing for enhancement of interfacial bonding so as to suppress interfacial debonding. Various parameters in this respect have been varied and their effect on the interfacial bond strength and thus on the Mode-I fracture toughness has been quantized. Experimental results, electrochemical characterization and optical/SEM observations of delaminated surfaces have established that anodization coupled with post curing results in an optimized interface between Aluminium alloy and Para-Aramid sheets. The optimization scheme described in this paper can be used to manufacture ARALL composites through low cost VARTM technology.

Experimental Comparison between Two Types of Hybrid Composite Materials in Compression Test

Abstract: In this study two groups of hybrid composite materials were experimentally studied in static uniaxial compression test. The first group consisted of Kevlar/glass fiber and the second group consisted of carbon/glass fiber reinforced epoxy resin. Each group contained four subsets (A, B, C and D) of hybrid composite materials. Compression test was carried out according to ASTM D695 and each test was replicated five times. It was observed that for the same type of hybrid composites, placing carbon or Kevlar fiber layers at the top and bottom; and glass fiber layers in the middle did not give significant effects than placing glass fiber layers at the top and bottom and carbon or Kevlar fiber layers in the middle of the specimens under compressive test. Furthermore, the results showed that hybrid composite laminates for the same number of layers with carbon/glass fiber provided the highest amount of the compressive stress value up to 40% compared to the results of the group which was reinforced with Kevlar/glass fiber.

Effect of Projectile Geometry on the Deformation Behavior of Kevlar Composite Armors Under Ballistic Impact

Abstract: A failure model based on the three-dimensional strains in a composite layer with improved progressive damage modeling has been implemented to predict the deformation behavior of composite armors subjected to ballistic impact. The present model comprises mainly of two parts. First, quadratic strain based failure criteria are presented to predict the initiation of failure modes. Second, the post damage softening behavior and degradation of the material stiffness is measured by damage evolution law. The model has been implemented within ABAQUS/Explicit as a user defined subroutine VUMAT. The validity of the model has been carried out by performing computational analysis of different composite armor materials such as Kevlar 29 and Kevlar 129 impacting with cylindrical-hemispherical nosed and 120° conical projectiles. It transpires that the predictions from the present model are in good agreement with the experimental and numerical observations available in the literature in terms of back face signature (BFS) for both the targets and projectiles. Further, the model has been implemented to study the effect of projectile geometry on the velocity time histories of the projectile, residual velocity and ballistic limit velocity. BFS values showed good agreement for conical projectile while for hemispherical projectile it is slightly low. The combination of Kevlar 129 armor and hemispherical projectile shows higher ballistic limit compared to that of the other combinations.

Comparison of tensile and compressive characteristics of intra/interply hybrid laminates reinforced high-density flexible foam composites

Abstract: The current study focused on fabrication and mechanical evaluation of intra/interply hybrid laminates–reinforced high-density flexible foam composites. The effects of composite thickness and expansion factor on the tensile and compressive characterization of the hybrid-laminated composites were experimentally investigated. Double face sheets were made of high-strength intra/interply hybrid laminates containing recycled Kevlar nonwovens and glass woven fabric. The results revealed that the hybrid laminates face sheet apparently promoted the tensile strength and tear resistance of the high-density flexible polyurethane foam. Tearing resistance in perpendicular direction exceeded more than twice the value in parallel direction. In terms of dynamic cushioning properties, cushioning force increased with the increase in composite thickness and the decrease in expansion factor, whereas the cushioning capacity loss, however, showed a different trend with the variation of the parameters. Most samples buffered more than 95% incident force under dynamic loading. Composite thickness and expansion factor exhibited significant influence on compression and indentation properties, including hardness, initial hardness factor, and indentation modulus. Except the composites with 10 mm thickness, the intra/interply hybrid laminated composites exhibited hysteresis loss of indentation force deflection ranging from approximately 30 to 38%, which was due to the fiber and thermal bonding point failure of hybrid laminates as unrecoverable damage. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41438.

Effect of hybridization on compressive properties of woven carbon, glass and kevlar hybrid composites

Abstract: The growing use of high-performance materials, which are made of hybrid composite systems, has increased rapidly in engineering applications. Hybridization of woven carbon, glass and Kevlar fibre offers better mechanical properties of composite materials. This is also an effective way to reduce the cost of advanced composites. At the moment information on compressive properties of hybrid composites is very limited. It is well known that the compressive strength of composite materials is lower than the tensile strength. Therefore, compressive strength becomes one of the most important criteria in designing composite structures. Therefore, this research is aimed to evaluate the compressive properties of hybrid composites and compare to the properties of neat systems. Hybrid composite samples were fabricated using a vacuum bagging system. The compressive properties of Kevlar hybrid with carbon and glass composites were studied using an INSTRON 3382 universal machine with a constant crosshead speed of 1 mm/min. The compressive properties were determined based on the stress-strain diagram. It was observed that for hybrid composites, placing carbon woven cloth layers in the exterior and Kevlar woven cloth in the interior showed higher compressive strength than placing glass woven cloth layers in the exterior and Kevlar woven cloth in the interior. The modes of failure of the hybrid composite laminates were observed and evaluated using optical microscope and scanning electron microscopy (SEM).

The Ballistic Performance of Multi-Layer Kevlar Fabrics Impregnated with Shear Thickening Fluids

Abstract: This study investigates the ballistic penetration performance of aramid fabric impregnated with shear thickening fluid. The ballistic test was conducted at impact velocity of 445 m/s, and three types of shear thickening fluids prepared with silica particles of different sizes (200nm, 340nm and 480nm) are involved. The results demonstrate an enhancement in ballistic properties of fabric due to the impregnation of shear thickening fluids. The fabrics with smaller particle size show better ballistic performance. Microscopic observation of aramid fabric reveals that shear thickening fluids with smaller silica particles have a better adhesion on and between yarns, enhancinging the coupling effect between yarns. The corresponding mechanism was discussed in the paper.

Effect of Alkaline Treatment on Tensile and Impact Strength of Kenaf/Kevlar Hybrid Composites

Abstract: This study is about the hybrid composite which used the woven Kevlar, long Kenaf fibre, and unsaturated polyester as the matrix. It focused on the mechanical characterization and properties of hybrid composite. The hybrid composites were fabricated by treated and untreated kenaf fibre and Kevlar as reinforcement in unsaturated polyester matrix using hand lay-up process. Effect of 6wt% of sodium hydroxide (NaOH) on the hybrid composites were analyzed using X-ray Diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR) analysis. The tensile and impact performance of the samples were tested according to the standard ASTM D3039 and ASTM D3763, respectively. Based on scanning electron micrograph (SEM) morphological examination, it revealed that the interfacial adhesion between the fibre surface and polymer matrix were improved. The results proved that the alkaline treatment can help to improve the mechanical properties compared to the untreated kenaf fibre.

Effect of hybridization on open-hole tension properties of woven kevlar/glass fiber hybrid composite laminates

Abstract: Hybrid laminates consisting of woven Kevlar/glass fiber composite plies were studied in terms of their residual tensile strength, stiffness and fracture surface. Residual tensile strength and stiffness were determined from the open hole tension test according to ASTM D5766. The laminates of Kevlar fiber reinforced polymer (KFRP), glass fiber reinforced polymer (GFRP) and hybrid of Kevlar-glass fiber reinforced polymer (KGFRP) were fabricated using a vacuum bagging process. Three different ratios of Kevlar to glass fiber plies were prepared in this study which were 20:80, 50:50, and 80:20. Results showed that hybrid laminate consisting of 80:20 Kevlar to glass fiber plies, produced higher residual tensile strength and stiffness when compared to the other hybrid system. Furthermore, strength and stiffness of hole specimens were reduced within 50-63% when compared to unhole specimens due to existence of the hole. In addition, the effect of adding nanosilica to the hybrid system was also studied. 5 wt% of nanosilica was added to the hybrid composite laminates and results showed that higher tensile strength and stiffness was observed in GFRP and 20:80 KGFRP specimens, while the tensile strength was decreased with an increased number of Kevlar fiber. This research was conducted as there are limited number of studies that have been done on the tensile strength of woven hybrid composite laminates so far, especially on hybridization of Kevlar and glass fiber with consideration on the effect of hole and addition of nanofillers.

Manufacturing and mechanical characterization of perforated hybrid composites based on flexible polyurethane foam

Abstract: This study focused on the fabrication and mechanical evaluation of nonwoven reinforced flexible polyurethane foam composites. Effects of perforation ratio, aperture size, and perforation depth on bursting and low-velocity impact responses of perforated composite panels were investigated. The nonwoven fabric used for cover sheet was composed of flame retardant polyester, low-melting point polyester, and recycled Kevlar staple fibers. Blending ratio of Kevlar fiber was confirmed to have relation to mechanical mechanism of cushioning layer. The highest mechanical strength value was obtained at 5 wt % of Kevlar ratio because of the highest cohesive force among recycled Kevlar, flame retardant polyester, and low-melting point polyester fibers was provided at the blending ratio. The perforated high-density flexible polyurethane foam composites panel was adhered with intra-ply hybrid laminates with various areal densities on each face to form sandwich structural composites. The results revealed that perforation ratio and aperture significantly influenced the bursting and low-velocity impact resistance behaviors of the perforated composites panel. Perforated composites with 10% perforation ratio and 4 mm aperture lead to maximum bursting strength of 437 N. Additional hybrid laminates significantly promoted the maximum bursting strength of the semiperforated hybrid composites by 212%. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42288.

Performance of kevlar fibre-reinforced rubber composite armour against shaped-charge jet penetration

Abstract: The protective capability of the Kevlar fibre-reinforced rubber composite armour (KFRRCA) at different obliquities is studied using depth-of-penetration experiments method against a 56 mm-diameter standard-shaped charge. Efficiency factors are calculated to evaluate the protection capability of the KFRRCA at different obliquities. Meanwhile, an X-ray experiment is used to observe the deformation, fracture, and scatter of the shaped-charge jet as it penetrates the composite armour. Finally, scanning electron microscopy (SEM) is used to analyse the effect of the Kevlar fibre-reinforced rubber for the composite armour to resist jet penetration. The results showed that the KFEECA can be used as additional armour, because it has excellent protection capability, and it can disturb the stability of the middle part of the shaped charge jet (SCJ) obviously especially when the armour at 30°and 68° obliquities.