COMPORTAMENTO MECÂNICO DO POLIETILENO DE ALTA DENSIDADE REFORÇADO COM NANOPLATAS DE GRAFENO E TECIDO DE JUTA: MECHANICAL BEHAVIOR OF HIGH-DENSITY POLYETHYLENE REINFORCED WITH GRAPHENE NANOPLATELETS AND JUTE FABRIC

Owing to sustainable characteristics, natural lignocellulosic fibers (FNLs) and graphene nanoplatelets (GNP)-reinforced composites are currently seeing applications in a wide range of industrial fields. Thus, in the present work, the mechanical, and flexural properties of high-density polyethylene (HDPE) reinforced with 0, 0.10, 0.25, and 0.50 wt.% of GNP combined with 50 vol.% of Juta fabric were investigated. In particular, the Juta/HDPE/0.25%GNP composite outperformed the strength of those described in the literature, even some with higher GNP. Enhancements of 38% were observed for the composite’s flexural modulus as compared to the GNP-free Juta/HDPE composite. Regarding the tensile properties, the ductility of the Juta/HDPE/0.25%GNP was increased by 112% when compared to the Juta/HDPE. Moreover, the toughness of the Juta/HDPE/0.25%GNP was 161% superior to the Juta/HDPE composite. SEM analysis of the fracture surfaces showed that, as GNP concentration rises, the fracture mechanisms change from shear band to a complex mixture of fibrillation, tearing, and crazing. Consequently, the results reveal the novel Juta/HDPE/0.25%GNP nanocomposite as a promising material for engineering applications.Debido a sus características sostenibles, las fibras lignocelulósicas naturales (FLN) y los compuestos reforzados con nanoplaquetas de grafeno (GNP) están siendo utilizados en una amplia gama de campos industriales. En este trabajo, se investigaron las propiedades mecánicas y de flexión del polietileno de alta densidad (HDPE) reforzado con 0%, 0.10%, 0.25% y 0.50% en peso de GNP combinado con 50% en volumen de tejido de yute. Se validaron estadísticamente las propiedades mecánicas y flexurales del polietileno de alta densidad (HDPE) reforzado con GNP y tejido de yute utilizando ANOVA y la prueba de Tukey. El proceso de extrusión seguido del prensado en caliente dio como resultado películas de nanocompuestos de HDPE reforzados con GNP que se utilizaron para fabricar las placas compuestas reforzadas con tejido de yute. En particular, se observó que el compuesto Jute/HDPE/0.25%GNP superó la resistencia de los compuestos descritos en la literatura, incluso algunos con mayor concentración de GNP. Se observaron mejoras del 38% en el módulo de flexión del compuesto en comparación con el compuesto Jute/HDPE sin GNP. En cuanto a las propiedades de tracción, se incrementó la ductilidad del Jute/HDPE/0.25%GNP en un 112% en comparación con el Jute/HDPE.Devido às características sustentáveis, as fibras lignocelulósicas naturais (FNLs) e os compósitos reforçados com nanoplaquetas de grafeno (GNP) estão atualmente tendo aplicações em uma ampla gama de campos industriais. Assim, no presente trabalho, foram investigadas as propriedades mecânicas e de flexão do polietileno de alta densidade (PEAD) reforçado com 0, 0,10, 0,25 e 0,50% em peso de GNP combinado com 50% em volume de tecido de juta. Em particular, o compósito JutaJuta/HDPE/0,25%GNP superou a resistência daqueles descritos na literatura, mesmo para alguns com maior GNP. Melhorias de 38% foram observadas para o módulo de flexão do compósito em comparação com o compósito de juta/HDPE livre de GNP. Com relação às propriedades de tração, a ductilidade da Juta/HDPE/0,25%GNP foi aumentada em 112% quando comparada à Juta/HDPE. Além disso, a tenacidade do compósito Juta/HDPE/0,25%GNP foi 161% superior à do compósito Juta/HDPE. A análise SEM das superfícies de fratura mostrou que, à medida que a concentração de GNP aumenta, os mecanismos de fratura mudam de uma banda de cisalhamento para uma mistura complexa de fibrilação, rasgo e fissura. Consequentemente, os resultados revelam o novo nanocompósito Juta/HDPE/0,25%GNP como um material promissor para aplicações em engenharia

COMPORTAMENTO MECÂNICO DO POLIETILENO DE ALTA DENSIDADE REFORÇADO COM NANOPLATAS DE GRAFENO E TECIDO DE JUTA: MECHANICAL BEHAVIOR OF HIGH-DENSITY POLYETHYLENE REINFORCED WITH GRAPHENE NANOPLATELETS AND JUTE FABRIC

Owing to sustainable characteristics, natural lignocellulosic fibers (FNLs) and graphene nanoplatelets (GNP)-reinforced composites are currently seeing applications in a wide range of industrial fields. Thus, in the present work, the mechanical, and flexural properties of high-density polyethylene (HDPE) reinforced with 0, 0.10, 0.25, and 0.50 wt.% of GNP combined with 50 vol.% of Juta fabric were investigated. In particular, the Juta/HDPE/0.25%GNP composite outperformed the strength of those described in the literature, even some with higher GNP. Enhancements of 38% were observed for the composite’s flexural modulus as compared to the GNP-free Juta/HDPE composite. Regarding the tensile properties, the ductility of the Juta/HDPE/0.25%GNP was increased by 112% when compared to the Juta/HDPE. Moreover, the toughness of the Juta/HDPE/0.25%GNP was 161% superior to the Juta/HDPE composite. SEM analysis of the fracture surfaces showed that, as GNP concentration rises, the fracture mechanisms change from shear band to a complex mixture of fibrillation, tearing, and crazing. Consequently, the results reveal the novel Juta/HDPE/0.25%GNP nanocomposite as a promising material for engineering applications.Debido a sus características sostenibles, las fibras lignocelulósicas naturales (FLN) y los compuestos reforzados con nanoplaquetas de grafeno (GNP) están siendo utilizados en una amplia gama de campos industriales. En este trabajo, se investigaron las propiedades mecánicas y de flexión del polietileno de alta densidad (HDPE) reforzado con 0%, 0.10%, 0.25% y 0.50% en peso de GNP combinado con 50% en volumen de tejido de yute. Se validaron estadísticamente las propiedades mecánicas y flexurales del polietileno de alta densidad (HDPE) reforzado con GNP y tejido de yute utilizando ANOVA y la prueba de Tukey. El proceso de extrusión seguido del prensado en caliente dio como resultado películas de nanocompuestos de HDPE reforzados con GNP que se utilizaron para fabricar las placas compuestas reforzadas con tejido de yute. En particular, se observó que el compuesto Jute/HDPE/0.25%GNP superó la resistencia de los compuestos descritos en la literatura, incluso algunos con mayor concentración de GNP. Se observaron mejoras del 38% en el módulo de flexión del compuesto en comparación con el compuesto Jute/HDPE sin GNP. En cuanto a las propiedades de tracción, se incrementó la ductilidad del Jute/HDPE/0.25%GNP en un 112% en comparación con el Jute/HDPE.Devido às características sustentáveis, as fibras lignocelulósicas naturais (FNLs) e os compósitos reforçados com nanoplaquetas de grafeno (GNP) estão atualmente tendo aplicações em uma ampla gama de campos industriais. Assim, no presente trabalho, foram investigadas as propriedades mecânicas e de flexão do polietileno de alta densidade (PEAD) reforçado com 0, 0,10, 0,25 e 0,50% em peso de GNP combinado com 50% em volume de tecido de juta. Em particular, o compósito JutaJuta/HDPE/0,25%GNP superou a resistência daqueles descritos na literatura, mesmo para alguns com maior GNP. Melhorias de 38% foram observadas para o módulo de flexão do compósito em comparação com o compósito de juta/HDPE livre de GNP. Com relação às propriedades de tração, a ductilidade da Juta/HDPE/0,25%GNP foi aumentada em 112% quando comparada à Juta/HDPE. Além disso, a tenacidade do compósito Juta/HDPE/0,25%GNP foi 161% superior à do compósito Juta/HDPE. A análise SEM das superfícies de fratura mostrou que, à medida que a concentração de GNP aumenta, os mecanismos de fratura mudam de uma banda de cisalhamento para uma mistura complexa de fibrilação, rasgo e fissura. Consequentemente, os resultados revelam o novo nanocompósito Juta/HDPE/0,25%GNP como um material promissor para aplicações em engenharia

Dynamic and Ballistic Performance of Uni- and Bidirectional Pineapple Leaf Fibers (PALF)-Reinforced Epoxy Composites Functionalized with Graphene Oxide

Replacing synthetic fibers with natural ones as reinforcement in polymeric composites is an alternative to contribute to sustainability. Pineapple leaf fibers (PALF) have specific mechanical properties that allow their use as reinforcement. Further, graphene oxide (GO) has aroused interest due to its distinctive properties that allow the improvement of fiber/matrix interfacial adhesion. Thus, this work aimed to evaluate the ballistic performance and energy absorption properties of PALF-reinforced composites, presenting different conditions (i.e., GO-functionalization, and variation of fibers volume fraction and arrangement) through residual velocity and Izod impact tests. ANOVA was used to verify the variability and reliability of the results. SEM was employed to visualize the failure mechanisms. The Izod impact results revealed a significant increase in the absorbed energy with the increment of fiber volume fraction for the unidirectional configuration. The ballistic results indicated that the bidirectional arrangement was responsible for better physical integrity after the projectile impact. Furthermore, bidirectional samples containing 30 vol.% of GO non-functionalized fibers in a GO-reinforced matrix showed the best results, indicating its possible application as a second layer in multilayered armor systems

Dynamic and Ballistic Performance of Graphene Oxide Functionalized Curaua Fiber-Reinforced Epoxy Nanocomposites

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

Ubim Fiber (Geonoma baculífera): A Less Known Brazilian Amazon Natural Fiber for Engineering Applications

The production of synthetic materials generally uses non-renewable forms of energy, which are highly polluting. This is driving the search for natural materials that offer properties similar to synthetic ones. In particular, the use of natural lignocellulosic fibers (NLFs) has been investigated since the end of 20th century, and is emerging strongly as an alternative to replace synthetic components and reinforce composite materials for engineering applications. NLFs stand out in general as they are biodegradable, non-polluting, have comparatively less CO2 emission and are more economically viable. Furthermore, they are lighter and cheaper than synthetic fibers, and are a possible replacement as composite reinforcement with similar mechanical properties. In the present work, a less known NLF from the Amazon region, the ubim fiber (Geonoma bacculifera), was for the first time physically characterized by X-ray diffraction (XRD). Fiber density was statistically analyzed by the Weibull method. Using both the geometric method and the Archimedes’ technique, it was found that ubim fiber has one of the lowest densities, 0.70–0.73 g/cm3, for NLFs already reported in the literature. Excluding the porosity, however, the absolute density measured by pycnometry was relatively higher. In addition, the crystallinity index, of 83%, microfibril angle, of 7.42–7.49°, and ubim fiber microstructure of lumen and channel pores were also characterized by scanning electron microscopy. These preliminary results indicate a promising application of ubim fiber as eco-friendly reinforcement of civil construction composite material

Ubim Fiber (<i>Geonoma baculífera</i>): A Less Known Brazilian Amazon Natural Fiber for Engineering Applications

The production of synthetic materials generally uses non-renewable forms of energy, which are highly polluting. This is driving the search for natural materials that offer properties similar to synthetic ones. In particular, the use of natural lignocellulosic fibers (NLFs) has been investigated since the end of 20th century, and is emerging strongly as an alternative to replace synthetic components and reinforce composite materials for engineering applications. NLFs stand out in general as they are biodegradable, non-polluting, have comparatively less CO2 emission and are more economically viable. Furthermore, they are lighter and cheaper than synthetic fibers, and are a possible replacement as composite reinforcement with similar mechanical properties. In the present work, a less known NLF from the Amazon region, the ubim fiber (Geonoma bacculifera), was for the first time physically characterized by X-ray diffraction (XRD). Fiber density was statistically analyzed by the Weibull method. Using both the geometric method and the Archimedes’ technique, it was found that ubim fiber has one of the lowest densities, 0.70–0.73 g/cm3, for NLFs already reported in the literature. Excluding the porosity, however, the absolute density measured by pycnometry was relatively higher. In addition, the crystallinity index, of 83%, microfibril angle, of 7.42–7.49°, and ubim fiber microstructure of lumen and channel pores were also characterized by scanning electron microscopy. These preliminary results indicate a promising application of ubim fiber as eco-friendly reinforcement of civil construction composite material

Water Immersion Aging of Epoxy Resin and Fique Fabric Composites: Dynamic&ndash;Mechanical and Morphological Analysis

Fiber-reinforced composites are among the most investigated and industrially applied materials. Many studies on these composites using fibers, especially with natural fibers, were made in response to an urgent action for ambient preservation. A particularly relevant situation exists nowadays in the area of materials durability. In this respect, no studies on water-immersion-accelerated aging in fique fiber&ndash;epoxy composites are reported. This work aimed to fill this gap by investigating the epoxy matrix composites reinforced with 40 vol% fique fabric. The epoxy matrix and the composite, both unaged and aged, were characterized by weight variation, water absorption, morphology, colorimetry (CIELAB method), Fourier transform infrared spectroscopy (FTIR) and dynamic&ndash;mechanical analysis (DMA). The main results were that degradation by water presents appearance of complex microfibril structures, plasticization of epoxy resin, and debonding of the fique fiber/epoxy matrix. The most intense color change was obtained for the water-immersion-aged epoxy by 1440 h. Cole&ndash;Cole diagrams revealed the heterogeneity of the materials studied

Ballistic Performance of Ramie Fabric Reinforcing Graphene Oxide-Incorporated Epoxy Matrix Composite

Graphene oxide (GO) incorporation in natural fiber composites has recently defined a novel class of materials with enhanced properties for applications, including ballistic armors. In the present work, the performance of a 0.5 vol % GO-incorporated epoxy matrix composite reinforced with 30 vol % fabric made of ramie fibers was investigated by stand-alone ballistic tests against the threat of a 0.22 lead projectile. Composite characterization was also performed by Fourier-transform infrared spectroscopy, thermal analysis and X-ray diffraction. Ballistic tests disclosed an absorbed energy of 130 J, which is higher than those reported for other natural fabrics epoxy composite, 74&ndash;97 J, as well as plain Kevlar (synthetic aramid fabric), 100 J, with the same thickness. This is attributed to the improved adhesion between the ramie fabric and the composite matrix due to the GO&mdash;incorporated epoxy. The onset of thermal degradation above 300 &deg;C indicates a relatively higher working temperature as compared to common natural fiber polymer composites. DSC peaks show a low amount of heat absorbed or release due to glass transition endothermic (113&ndash;121 &deg;C) and volatile release exothermic (~132 &deg;C) events. The 1030 cm&minus;1 prominent FTIR band, associated with GO bands between epoxy chains and graphene oxide groups, suggested an effective distribution of GO throughout the composite matrix. As expected, XRD of the 30 vol % ramie fabric-reinforced GO-incorporated epoxy matrix composite confirmed the displacement of the (0 0 1) peak of GO by 8&deg; due to intercalation of epoxy chains into the spacing between GO layers. By improving the adhesion to the ramie fabric and enhancing the thermal stability of the epoxy matrix, as well as by superior absorption energy from projectile penetration, the GO may contribute to the composite effective ballistic performance