Images of typical personal body armour [59]

Images of typical personal body armour [59]

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The need to provide a better and stronger protection against various kinds of ballistic impacts and threats has necessitated the continuous exploration and utilization of high-performance fibres, especially those that are derived from renewable sources for ballistic applications. The development of ballistic protection materials with improved perfo...

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... Single fiber tests have allowed obtaining tensile strength and elastic modulus for the two types of fibers obtained in this work; fibers from stems show an average strength of around 905 MPa, varying from 600 to 1200 MPa, and an elastic modulus close to 42 GPa (31-56 GPa). Fiore and collaborators (Fiore, Scalici, and Valenza 2014) reported 248 MPa and 9.4 GPa for fibers obtained from stems, which are quite lower than those shown here and those reported for other natural fibers, such as abaca (400-980 MPa; 8-20 GPa), jute (393-773 MPa; 27 GPa), flax (345-1035MPa; 28 GPa) or bamboo (140-1000 MPa, 11-89 GPa) (Odesanya et al. 2021). ...
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This work describes an extraction method for giant reed fibers from stems and leaves based on chemical soaking and crushing through a rolling mill. Obtained fibers, together with the shredded plant (stems + leaves), are characterized in terms of chemical composition, thermal stability, morphology, and crystallinity. Mechanical properties of fibers have also been assessed (single fiber tensile tests). The results show that the proposed method allows obtaining fibers with higher cellulose content (near 70%), good thermal stability (10% weight loss over 270°C), higher density, and better mechanical properties than other Arundo fibers previously reported in the literature. Fibers from leaves are thinner and show higher crystallinity than those from stems (72 μm vs. 157 μm, 73% vs. 67% crystallinity, respectively), although mechanical properties are similar for both (around 900 MPa for tensile strength and over 45 GPa for elastic modulus). Analysis of the microstructure shows that fibers consist of microfiber bundles, and the removal of a thin layer of non-cellulosic nature is clear; fibers provide a rougher, cleaner surface than shredded raw material.
... It can be used in medical applications like scaffolds, drug delivery, and tissue engineering. [16][17][18][19][20][21][22][23][24][25][26][27][28][29] Bio-composites consisting of natural fibers as reinforcing elements with a biodegradable matrix are green products derived from natural resources, have a very long life, and are completely biodegradable after use. They are less toxic, easy to fabricate, and have a very good strength-to-weight ratio. ...
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Nettle and Poly Lactic Acid (PLA) fibers are the strongest and best fibers with valuable potential as reinforcement in a composite. In this study, the development and characterization of a multi-layered laminated fibre reinforced bio-composite from nettle and PLA fiber were performed. Prior to molding, the nettle fibers were treated with chemicals such as Alkali and silane and the influence of chemical treatment on the property of nettle fibers were investigated. The characteristics of raw and chemically treated nettle fibers were investigated through chemical composition analysis, mechanical properties, Fourier transform infrared spectroscopy, scanning electron microscopy and water sorption test. Furthermore physical and mechanical properties of the nettle/PLA bio-composite have been analyzed. Twenty (20) samples of treated and untreated nettle fiber and five samples of nettle/PLA fiber reinforcement bio-composites were tested and the results were averaged for comparison with one another. Based on the results obtained, the treated fiber improves tensile strength, has a more uniform and smaller diameter, a clean surface, and has a good appearance compared to untreated fiber. Laminated bio-composites were found to increase initially with the increase of nettle fiber content till 50 weight % and decrease afterwards. Generally, the bio-composite prepared with an equal weight proportion of nettle and poly lactic acid fiber obtained better mechanical properties and tensile strength. Water sorption test results showed that water uptake ability of treated nettle fibers were lower than raw nettle fibers.
... It can be used in medical applications like scaffolds, drug delivery, and tissue engineering. [16][17][18][19][20][21][22][23][24][25][26][27][28][29] Bio-composites consisting of natural fibers as reinforcing elements with a biodegradable matrix are green products derived from natural resources, have a very long life, and are completely biodegradable after use. They are less toxic, easy to fabricate, and have a very good strength-to-weight ratio. ...
... This MAS second layer also absorbs a significant amount of remaining energy associated with the cloud of ceramic and projectile fragments [14]. In addition to conventional synthetic materials such as aramid fabric (Kevlar or Twaron), which for long time have been applied as a MAS second layer [15], natural lignocellulosic fiber (NLF) composites have recently been considered as promising alternatives [16][17][18][19]. ...
... Twaron), which for long time have been applied as a MAS second layer [15], natu lignocellulosic fiber (NLF) composites have recently been considered as promis alternatives [16][17][18][19]. ...
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Buriti Fibers extracted from the leafstalk of palm tree, Mauritia flexuosa, native to the Amazon region, have been investigated as a reinforcement of polymer matrix composites. Recently, the fabric made from buriti fibers was also studied as a possible reinforcement of epoxy composites. In particular, the preliminary results of a 10 vol% buriti fabric epoxy composite in a multilayered armor system (MAS) displayed a satisfactory backface signature (BFS) but the composite target was not able to preserve its integrity after the ballistic impact. This motivated the present work, in which we carry out a complete statistical investigation of the ballistic performance of 10, 20, and 30 vol% buriti fabric epoxy composites as a MAS second layer against 7.62 mm rifle ammunition. BFS, associated with the depth of penetration in a clay witness simulating a human body, disclosed values of 18.9 to 25 mm, statistically similar and well below the lethal value of 44 mm specified by the international standard. Absorbed energy in stand-alone ballistic tests of 163–190 J for armor perforation were also found to be statistically higher than 58 ± 29 J obtained for the conventionally applied synthetic aramid fabric. The 30 vol% buriti fabric composites maintained the integrity of the MAS second layer, as required for use in body armor. Failure mechanisms found for the 10 vol% and 20 vol% buriti fabric composites by macro analysis and scanning electron microscopy confirmed the importance of a higher amount such as 30 vol% in order to achieve effective ballistic protection.
... Due to its abundance, renewability and interesting properties (low density, high strength, high tensile modulus, ecology, durability…), cellulose has many applications in various fields: pharmaceuticals, chemical feedstocks, paper manufacturing and liquid fuel production [18][19][20][21][22][23]. In this regard, a number of researchers have been conducted to study the use of lignocellulosic fibers. ...
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The exploitation of biomass represents a major environmental challenge related to the protection of the environment and the progressive exhaust of fossil resources. In this perspective, the main objective of this work is the extraction and the characterization of natural lignocellulosic fibers from the Schinus molle. The cellulose fibre extraction was investigated employing conditions of alkali treatment. After the alkaline steps, a bleaching treatment was done and let to a yield about 45% pure cellulose. The identification of the chemical composition of Schinus molle reveals that this raw material contains a high level of biopolymers with a cellulose rate of 53.2%. Extracted cellulose fibers have been characterized by several techniques such as scanning electron microscopy, Fourier transform infrared, X-ray diffraction, Morfi, and by the determination of their degree of polymerization. FT-IR results confirm the purity of the cellulosic fibers, and XRD analysis reveals that the crystallinity increases after the delignification and bleaching treatments.
... As a MAS ballistic second layer, NFL composites display relevant advantages. Indeed, they are environmentally sustainable as well as cost-effective and easy to manufacture [17][18][19][20][21][22]. However, there are disadvantages concerning the surface morphology and the compatibility of natural fibers with polymer matrices; these might impair the integrity of the ballistic target material. ...
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Graphene oxide (GO) functionalized curaua fiber (CF) has been shown to improve the mechanical properties and ballistic performance of epoxy matrix (EM) nanocomposites with 30 vol% fiber. However, the possibility of further improvement in the property and performance of nanocomposites with a greater percentage of GO functionalized CF is still a challenging endeavor. In the present work, a novel epoxy composite reinforced with 40 vol% CF coated with 0.1 wt% GO (40GOCF/EM), was subjected to Izod and ballistic impact tests as well as corresponding fractographic analysis in comparison with a GO-free composite (40CF/EM). One important achievement of this work was to determine the characteristics of the GO by means of FE-SEM and TEM. A zeta potential of −21.46 mV disclosed a relatively low stability of the applied GO, which was attributed to more multilayered structures rather than mono- or few-layer flakes. FE-SEM images revealed GO deposition, with thickness around 30 nm, onto the CF. Izod impact-absorbed energy of 813 J/m for the 40GOCF/EM was not only higher than that of 620 J/m for the 40CF/EM but also higher than other values reported for fiber composites in the literature. The GO-functionalized nanocomposite was more optimized for ballistic application against a 7.62 mm projectile, with a lower depth of penetration (24.80 mm) as compared with the 30 vol% GO-functionalized CF/epoxy nanocomposite previously reported (27.43 mm). Fractographic analysis identified five main events in the ballistic-tested 40GOCF/EM composed of multilayered armor: CF rupture, epoxy matrix rupture, CF/matrix delamination, CF fibril split, and capture of ceramic fragments by the CF. Microcracks were associated with the morphological aspects of the CF surface. A brief cost-effective analysis confirmed that 40GOCF/EM may be one of the most promising materials for personal multilayered ballistic armor.
... From reported works, the obtained fibers can be incorporated in various synthetic matrix materials such as epoxy, vinyl ester, phenolic, polypropylene, and biodegradable polymer matrix materials such as Poly-lactic acid (PLA) are also used [26][27][28][29][30][31][32]. There are several parameters to control the compatibility of fibres with matrix materials include type, loadings, surface area and aspect ratio. ...
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In this century, the development of nano-sized filler from biomass material has become the main focus of industries in achieving their final green composite product for a wide range of applications. From a commercial and environmental point of view, fragmentation and downsizing of waste lignocellulosic fibers without chemical treatments into small size particles is a viable option. In this study, an attempt was made to produce nano-sized lignocellulosic fillers from date palm micro fibers via mechanical ball milling process at intense 99 cycles run (equivalent to 25 h). The resultant nanofillers as well as the microfibers were characterized in details by various analytical techniques, including transmission electron microscopy (TEM), scanning electron microscopy (SEM), particle size analysis (PSA), Energy Dispersive X-Ray (EDX), X-ray diffraction (XRD), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC) to assess their structure—property relationship. From microscopy examination, the nanofillers showed a heterogeneous mix of irregular shaped particles, and while having a size ranging of 30–110 nm in width and 1–10 mm length dimensions. Also, the crystallography analysis revealed the crystallinity had mildly declined from microfibers (71.8%) to nanofiller (68.9%) due to amorphization effect. As for thermal analysis, the nanofillers exhibited high heat resistance at 260.8 °C decomposition temperature. Furthermore, the nanofillers also had stable thermo-changing behavior by presenting low heat enthalpy change (40.15 J/g) in its endothermic reaction for breaking organic bonds. The thermal results suggest its suitability for composite fabrication process at high temperature. Thus, the produced nanofillers can be used as a low cost reinforcing agent in the future for versatile polymer-based composite systems.
... The use of NFRPC is expected to grow in the future for specific applications, for example, use of light-weight natural fiber composites in ballistic armor [31][32][33]. In this case, thermal aging might play an important role in the armor expiration time. ...
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Citation: Oliveira, M.S.; da Luz, F.S.; da Costa Garcia Filho, F.; Pereira, A.C.; de Oliveira Aguiar, V.; Lopera, H.A.C.; Monteiro, S.N. Dynamic Mechanical Analysis of Thermally Aged Fique Fabric-Reinforced Epoxy Composites. Polymers 2021, 13, 4037. https:// Abstract: Dynamic mechanical analysis (DMA) is one of the most common methods employed to study a material's viscoelastic properties. The effect of thermal aging on plain epoxy and a fique fabric-reinforced epoxy composite was investigated by comparing the mass loss, morphologies, and DMA properties of aged and unaged samples. In fact, thermal aging presents a big challenge for the high-temperature applications of natural fiber composites. In this work, both plain epoxy and fique fabric-reinforced epoxy composite were found to have different molecular mobility. This leads to distinct transition regions, with different changes in intensity caused by external loadings from time-aging. Three exponentially modified Gauss distribution functions (EMGs) were applied to loss factor curves of fique fabric-reinforced epoxy composite and plain epoxy, which allowed identifying three possible mobility ranges. From these results it was proposed that the thermal degradation behavior of natural fibers, especially fique fiber and their composites, might be assessed, based on their structural characteristics and mechanical properties.
... In the defence industry, natural fibers are used as an alternative in replacing Kevlar fibers. For instance, they were used in the Multilayered Armour System (MAS) due to their high impact energy absorption, lowweight, and efficiency in capturing splinters from the ceramic plate typically present in MAS [164]. The curauá based natural fibers reinforced composites, for example, are up-and-coming solutions for these applications as they are being intensely studied recently to be applied in military equipment mainly due to their excellent relationship between weight and strength [165,166]. ...
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Natural fibre-reinforced polymer composites (NFRCs) have demonstrated great potential for many different applications in various industries due to their advantages compared to synthetic fiber-reinforced composites, such as low environmental impact and low cost. However, one of the drawbacks is that the NFRCs present relatively low mechanical properties and the absorption of humidity due to the hydrophilic characteristic of the natural fibre. One method to increase their performance is hybridization. Therefore, understanding the properties and potential of using multiple reinforcement's materials to develop hybrid composites is of great interest. This paper provides an overview of the recent advances in hybrid natural fiber reinforced polymer composites. First, the main factors that affect the performance of hybrid fiber-reinforced composites were briefly discussed. The effect of hybridization on the mechanical and thermal properties of hybrid composites reinforced with several types of natural fibers (i.e., sisal, jute, curauá, ramie, banana, etc.) or natural fibers combined with synthetic fibers is presented. Finally, the water absorption behaviour of hybrid fiber-reinforced composites is also discussed. It was concluded that the main challenges that need to be addressed in order to increase the use of natural-natural or natural-synthetic hybrid composites in the industry are the poor adhesion between natural fibers and matrix, thermal stability and moisture absorption of natural fibers. Some of these challenges were addressed by recent development in fibers treatment and modification, and product innovation (hybridization).
... However, the main advantages of natural fibers include low cost, low density, nonabrasive to the equipment, non-irritative to the skin, reduced energy consumption, less health risk, renewability, recyclability, and biodegradability. 2,4,[16][17][18] Their processing is environmentally friendly, offering better working conditions and therefore, a reduction in risk of dermal or respiratory problems compared with synthetic fibers. The most interesting aspect of natural fibers is their positive environmental impact. ...
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Recently development of high-performance polymer composites made from natural resources in the various sectors is increasing tremendously due to the environmental issues and health hazard possessed by the synthetic fibers during disposal and manufacturing. Among the many different types of natural resources, kenaf fibers have been extensively investigated as an alternative reinforcement for polymer composites over the past few years due to their low cost, good mechanical properties, high specific strength, nonabrasive, eco-friendly, and biodegradability characteristics. Kenaf is regarded as an industrial crop in Malaysia and grown commercially in other parts of the world for different applications. It is certainly one of the important plants cultivated for natural fibers globally which has great potential to use as automotive and construction materials. In many research studies, kenaf fibers have been used as reinforcement in unsaturated polyester (UPE) which perfectly improved the features of the polyester resin. The tensile properties of kenaf fiber reinforced UPE are mainly influenced by the interfacial adhesion between the fibers and the polyester resin. Several chemical modifications are employed to improve the interfacial bonding between kenaf fibers and polyester, resulting in the enhancement of mechanical properties of the composites. Therefore, this paper explores and highlights of the previous studies around kenaf fiber reinforced UPE composites, in terms of processing methods, mechanical, water absorption, and morphological properties to provide a perfect source of literature for doing further research in this topic.