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This review provides an overview of use of natural fibers and potential use of rice straw fibers as reinforcement in composite. As it is known that after china, India is the second largest country in the world producing rice as food grains. As a result of producing more amount of rice a large amount of rice straw is left as a residue, some of which is used for fodder feeding and a large amount of which is just burned by the farmers .This burning off practice is very common in the country because it is the cheapest way in which farmers can rid of the waste material, It can be seen that every year our national capital gets into a cover of smog because of burning of parali (rice straw). Scientists have understood the potential of using rice straw natural fiber in place of wood fiber in various uses, hence many experimental labs and commercial research is being conducted in this field and a lot of startups are also being initiated on this. Various composites are being made and their properties are being tested in various parts of the world. These composites are mainly termed as green composites. These green composite have great potential in preventing our environment, giving sustainable replacement towards use of plastic, wood and all other materials in industrial use.

Synthetic plastics have several concerns for the environment, such as their impact on climate change, their long degradation time, or their degradation to microplastics that threaten animal life in the sea. The application of natural fibers as reinforcement in synthetic polymeric matrixes has several advantages in properties such as low density, lower cost of production, biodegradability, and a reduction of the environmental impact in the polymer industry. In this study, the Ecuadorian Guadua Angustifolia Kunth fiber was extracted and treated physically and chemically for its use as reinforcement in composite preparation. Maleic anhydride was used as a coupling agent to improve the interaction between the natural fiber and the low-density polyethylene (LDPE) polymeric matrix. The composite production was done using different bamboo particle loading (1-5% w/w) at a constant particle size (150 μm). Chemical, physical, and mechanical properties were evaluated to characterize the fiber and biocomposites. The chemical treatment of the fiber with 2% of NaOH showed a reduction of the lignin content confirmed by Fourier-Transform infrared spectroscopy. A total of ~39% mass loss related to the lignin, waxes, and other organic content was reached. In addition, a reduction in the density from approximately 0.87 to 0.66 was shown when increasing the content of bamboo in the composite. In the same way, the crystallinity was reduced by 3%. The composite with 1% bamboo presents a tensile strength of 10,66 MPa. The use of bamboo fiber in the biocomposites reduces the global warming potential concerning the increasing amount of fiber.

One of the most common load modes is flexure. The paper measures and models the flexural strength and modulus of a bio-polyethylene reinforced with thermos-mechanical fibers from corn stover. Moreover, the authors use modified rules of mixtures to evaluate the contribution of the reinforcements to the properties of the composite. It was found a high impact of coupling agent content on the strength of the composites, and materials with a 6% of such agent and 50% of reinforcement increased 181% the strength of the matrix, and 464% its modulus. The obtained values are noticeable higher than polypropylene and some of its composites. Micromechanics analysis shows that the effect of natural fiber reinforcement on the flexural properties of a bio-based PE is similar to the effects on a polyolefin. Thus, the use of fully bio-based composites can be proposed as a substitute for some oil-based polymers, partially bio-based materials, and their composites

Fiber-reinforced polymer composites are well-studied and established products, and today they are being used in different industrial and non-industrial areas. However, the increased interest in recyclability and the concerns about climate change caused materials scientists to look for a non-petroleum-based alternative to synthetic fibers and polymers. Since the beginning of this century, natural fibers and biopolymers have attracted increasing interest each year for composite applications. Thanks to this interest, studies on natural fibers and biopolymers have increased significantly. Despite the high number of studies on natural fibers and natural fiber-reinforced polymers (NFRP), there are gaps in the literature. This work reviews studies on natural fibers, biopolymers, and biocomposites with their advantages, disadvantages, and limitations. Studies that focus on the ways to reduce or eliminate these disadvantages and limitations have also been looked at. Also, current challenges and future perspectives for natural fibers, biopolymers, and NFRPs have been discussed.

Prirodna vlakna sve su češća zamjena za do tada tradicionalne vrste ojačala u izradi kompozitnih materijala. Ekologija i kružno gospodarstvo utjecali su na porast biljnih vlakana u tehnologijama proizvodnje zbog njihovih mehaničkih svojstava, recikličnosti, maloga utjecaja na okoliš, male emisije CO2 i širenja privrede na zabačene dijelove svijeta u kojima se ljudi još uvijek bave agrokulturom. Sama prirodna vlakna nemaju dovoljno dobra mehanička svojstva za primjenu u svim područjima strojarstva te se hibridizacijom miješaju sa staklenim vlaknima kako bi se utjecalo na njegov porast. Cilj ovoga rada bio je ispitati utjecaj hibridizacije lanenih vlakana staklenima u epoksidnoj matrici i uvidjeti utjecaj vode na mehaničko ponašanje takvih materijala. Voda je najmanje utjecala na mehanička svojstva kompozita koji su samo od staklenih vlakana ili su vlakna s vanjske strane materijala te su takva svojstva zamjetljiva i na mehaničkim svojstvima. Uzorcima koji su bili u vodi smanjio se modul, a rastezna su i savojna čvrstoća jedino porasle kod materijala sa SSSSSS i SLLLLS konfiguracijom. Natural fibers are an increasingly common substitute for previously traditional types of reinforced composite materials. Ecology and the circular economy have influenced the growth of plant fibers in production technologies due to their mechanical properties, recyclability, low impact on the environment, low CO2 emissions and the expansion of the economy to remote parts of the world where people still engage in agriculture. Natural fibers alone do not have good enough mechanical properties for application in all areas of mechanical engineering, so they are mixed with glass fibers through hybridization in order to influence its growth. The aim of this work was to examine the influence of the hybridization of flax fibers with glass in an epoxy matrix and to see the influence of water on the mechanical behavior of such materials. Water had the least effect on composites that are only made of glass fibers or the fibers are on the outside of the material, and such properties are also noticeable in the mechanical properties. The modulus of the samples that were in water decreased, while the tensile and flexural strength only increased in materials with SSSSSS and SLLLLS configuration due to better fiber adhesion and their protection against water penetration.

Natural fibers do not have a long life in soil; therefore, they cannot replace synthetic textiles in many applications. However, in order to solve ever-increasing global environmental problems due to microplastics, more and more natural polymers must be used, creating a need for research into the sustainable life extension of natural fibers. Lignin is, along with cellulose, a main component of wood, and is produced in large quantities as waste during paper production. With appropriate processing, lignin can be exploited/used as a textile auxiliary to combine the strength-enhancing properties of textiles made from natural fibers with the protective properties of a lignin coating. However, there is not yet sufficient research on how to integrate lignin into textile applications. For this purpose, in this study, we have investigated whether thermoplastic lignin can be processed as a surface protective coating. We tested lignin as a yarn coating to extend the service life of cellulosic textiles. Cotton yarns have been coated with lignin in variations of coating mass, characterized and investigated by means of soil burial tests. As the soil burial tests conducted in climate chamber and outdoor field environments showed, the lifespan of textiles made from natural fibers can be significantly extended with a lignin coating. Long-term resilience has been demonstrated in standard burial tests. In the outdoor tests, the lignin coating was still fully intact, even after about 160 days of burial. The textile materials coated in this way enable sustainable applications, especially for geotextiles. They have an adjustable, sufficiently long service life; however, they are still biodegradable, and can therefore replace some applications, such as vegetating trench/brook slopes, with synthetic materials. Lignin-coated textiles have the potential to significantly reduce the carbon footprint, reduce not only the dependence on petroleum-based products but also the amount of microplastics entering the environment. Further research can be conducted to improve lignin compounding in terms of other interesting properties for specific textile applications. Process optimization could increase the protective effect and further extend the life of useful textiles in soil.

Composite materials containing natural reinforcement fibers, generally called biocomposites, have attracted the interest of both researchers and manufacturers, but the most environmentally advantageous combinations include a bio-based matrix, as well. With this in mind, a poly(lactic acid) (PLA) matrix was reinforced with natural fibers from hemp, both untreated strands (UHSs) and soda-bleached fibers (SBHFs). The preparation of the subsequent fully bio-sourced, discontinuously reinforced composites involved kinetic mixing, intensive single-screw extrusion, milling, and injection molding. Up to a fiber content of 30 wt%, the tensile modulus increased linearly with the volume fraction of the dispersed phase. Differences between SBHFs (up to 7.6 Gpa) and UHSs (up to 6.9 Gpa) were hardly significant (p = 0.1), but SBHF-reinforced composites displayed higher strain at failure. In any case, for the same fiber load (30 wt%), the Young’s modulus of PLA/hemp biocomposites was greater than that of glass fiber (GF)-reinforced polypropylene (5.7 GPa), albeit lower than that of PLA/GF (9.8 GPa). Considering all the measurements, the contribution of each phase was analyzed by applying the Hirsch model and the Tsai-Pagano model. As a concluding remark, although the intrinsic tensile modulus of SBHFs was lower than that of GF, the efficiency of those natural fibers as reinforcement (according to the rule of mixtures) was found to be higher.

Properties of sisal fibers such as high coarseness and poor drapability made the fibers less suitable in production of conventional textiles compared to synthetic fibers. The environmental consciousness and depletion of petrochemical resources have attracted researchers on investigating the use of natural fibers in the industrial production of conventional textiles. Sisal is among highly researched natural fibers due to its features such as strength, recyclability, availability, low processing cost, light weight and ease process ability. This paper reviews possible modifications of sisal fibers to enhance performance in conventional textiles applications.

This paper discusses the challenges in using natural fibers for the development of textile-reinforced mortar (TRM) composites with pseudo-strain-hardening and multiple cracking behavior. The particular characteristics of natural vegetal fibers are analyzed with reference to data from the literature. It is concluded that the efficient use of these fibers as composite reinforcement requires the development of treatment or impregnation protocols for overcoming durability issues, eliminating crimping effects in tensile response and imparting dimensional stability. Relevant experimental research on the synthesis and performance of natural TRMs is reviewed, showing that the fabrication of such systems is, at present, largely based on empirical rather than engineering design. In order to set a framework regarding the properties that the constituents of natural TRM must meet, a comparative analysis is performed against inorganic matrix composites comprising synthetic, mineral and metallic reinforcement. This highlights the need for selecting matrix materials compatible with natural fibers in terms of stiffness and strength. Furthermore, a rational methodology for the theoretical design of natural TRM composites is proposed. First-order analysis tools based on rule-of-mixtures and fracture mechanics concepts are considered. Based on the findings of this study, paths for future research are discussed.

Günümüz tüketicileri giysi tercihlerini yaparken görünümünün yanında sağladıkları konfor özellikleri ile ilgilenmektedirler. Son yıllarda yapılan tüketici tercihi araştırmaları, satın alma tercihlerinde giysi konforunun ve ilgili kumaş özelliklerinin payının arttığını göstermektedir. Konfor tanımlanması kompleks ve güç bir olgudur. Bir kişinin kendini konforlu hissedebilmesi için giydiği giysiden ve/veya çevreden herhangi bir uyaranın beyne iletilmemiş olması gerekir. Bu açıdan konfor kavramı psikolojik, fiziksel, termal ve hareket konforu gibi birçok özelliği içermektedir. Günümüzde tüketiciler doğal kaynaklı malzemelere daha fazla önem vermeye başlamıştır. Değişen kullanıcı beklentileri denim giysilerin konfor özelliklerini ön plana çıkarmaktadır. Özellikle gömlek ve elbise yapımında ya da çocuk giysilerinde kullanılmakta olan düşük birim alan kütlesine sahip denim kumaşlar için dokunsal konfor oldukça önemlidir. Bu gerçekten yola çıkarak bu tezde; farklı doğal malzemelerin özellikle konfor açısından avantajlarını kullanarak konforlu denim kumaşlar geliştirilmesi amaçlanmıştır. Tencel, modal, soya proteini ve kaşmir liflerinin denim kumaş yapısında pamuk ile birlikte kullanılıp, 4 farklı denim yıkama kullanılarak geliştirilen yüksek dokunsal konfor özelliklerine sahip denim kumaşların, dokunsal konfor özelliklerinin bilimsel yöntemlerle ölçülmesinin yanı sıra kantitatif olarak ifade edilmesi ve karşılaştırmalarının yapılması hedeflenmiştir. Yapılan bu çalışmada tüm verilerin değerlendirilmesi sonucunda denim kumaşların dokunsal konfor özelliklerini lif tipi, dokuma yönü ve yıkama tipinin etkili olduğu görülmüştür. The consumers of today, interests with comfort properties beside of apperance when makes the clothing preferences. The consumers preferences survey in recent years indicates that related fabric properties and clothing comfort effects the ratio of increasement of purchasing preference. The definition of comfort is complex and hard explainable fact. For to feel comfortable any stimulus from the clothing and/or environment must not be transmitted to the brain. In this respect, the comfort includes many features such as psychological, physical, thermal and movement comfort. Today, consumers have begun to give more importance to materials of natural origin. Changing user expectations are highlight the comfort features of denim clothing. Tactile comfort is very important especially for denim fabrics with low unit area mass, which are used in shirts and dresses or children's clothing. Based on this fact, in this thesis; It is aimed to develop comfortable denim fabrics by using the advantages of different natural fibers, especially in terms of comfort. It is aimed to quantitatively express and compare the tactile comfort properties of denim fabrics with high tactile comfort properties, which are developed by using tencel, modal, soy protein and cashmere fibers together with cotton in the denim fabric structure and using 4 different denim washes. In this study as a result of the evaluation of all the data, it was seen that fiber type, weaving direction and washing type were effective on the tactile comfort properties of denim fabrics.

Many studies available in the literature focus mainly on the mechanical characterization of fiber, leaving out other physicochemical and thermogravimetric analyses that allow for establishing its potential as an engineering material. This study characterizes fique fiber for its potential use as an engineering material. The fiber’s chemical composition and physical, thermal, mechanical, and textile properties were analyzed. The fiber has a high holocellulose content and low lignin and pectin content, indicating its potential as a natural composite material for various applications. Infrared spectrum analysis revealed characteristic bands associated with multiple functional groups. The fiber had monofilaments with diameters around 10 μm and 200 μm, as determined by AFM and SEM images, respectively. Mechanical testing showed the fiber could resist a maximum stress of 355.07 MPa, with an average maximum strain at which breakage occurs of 8.7%. The textile characterization revealed a linear density range of 16.34 to 38.83 tex, with an average value of 25.54 tex and a regain of 13.67%. Thermal analysis showed that the fiber’s weight decreased by around 5% due to moisture removal in the range of 40 °C to 100 °C, followed by weight loss due to thermal degradation of hemicellulose and glycosidic linkages of cellulose ranging from 250 to 320 °C. These characteristics suggest that fique fiber can be used in industries such as packaging, construction, composites, and automotive, among others.

Hemp fibers produced by different extraction techniques that were cultivated in the Portuguese districts of Bragança and Mirandela under various nitrogen fertilization and planting density conditions are examined and mechanically described in this paper. The objective of this study is to evaluate the influence of sowing density, nitrogen fertilization, sample location, and extraction method in order to improve the mechanical properties of hemp fibers. To achieve this, we determined the modulus of elasticity, the tensile strength, and the density. The mean value for the modulus of elasticity was 92.44 ± 7.44 GPa, the mean of tensile strength was 564.98 ± 167.03 MPa, and the mean of the density was 1.64 ± 0.24 g cm−3. We performed a statistical analysis of all parameters using ANOVA and found that the retting method had the greatest influence among all parameters. The associated effects of nitrogen fertilization and sowing density revealed an important influence on tensile strength and specific tensile strength, respectively.

There is an increasing desire to use natural products that will be both effective and biodegradable. The aim of this work is to investigate the effect of modifying flax fibers with silicon compounds (silanes and polysiloxanes), as well as examining the effect of the mercerization process on their properties. Two types of polysiloxanes have been synthesized and confirmed by infrared spectroscopy (FTIR) and nuclear magnetic resonance spectroscopy (NMR). Scanning electron microscopy (SEM), FTIR, thermogravimetry analysis (TGA) and pyrolysis-combustion flow calorimetry (PCFC) tests of the fibers were performed. On the SEM pictures, flax fibers purified and covered with silanes were visible after treatment. FTIR analysis showed stable bonds between the fibers and the silicon compounds. Promising results of thermal stability were obtained. It was also found that modification had a positive effect on the flammability. The conducted research showed that the use of such modifications, in the context of using flax fibers for composites, can yield very good results.

Uvod: Za izdelavo ortoz in protez pogosto uporabljamo plastiko in polimerne kompozite z ogljikovimi vlakni. V današnjem času pa so zaradi vse večjega povpraševanja po okolju prijaznih materialih in želji po znižanju cen kompozitnih materialov raziskovalci začeli posvečati pozornost naravnim vlaknom in matricam naravnega izvora. Namen: Glavni namen diplomskega dela je bil prepoznati in preučiti materiale na naravni osnovi, ki se uporabljajo pri izdelavi ortoz in protez. Metode dela: Za pisanje diplomskega dela je bila uporabljena deskriptivna metoda za iskanje domače in tuje internetne literature. Zbrano literaturo, ki je v angleškem jeziku smo iskali v različnih podatkovnih bazah kot so Science Direct, PubMed, Google Schoolar in Cochrane Library. Rezultati: Uporaba materialov iz naravnih virov se je po vsem svetu povečala zaradi okoljskih vidikov in gospodarskih koristi v primerjavi z uporabo neobnovljivih virov. Prednosti kompozitov iz naravnih vlaken so večja elastičnost, biološka razgradljivost, prijaznost do okolja in cenovne ugodnosti, izkazujejo pa tudi veliko trdnost, togost in korozijsko odpornost. Razprava in zaključek: Na podlagi študij smo ugotovili, da so naravna vlakna primerna za izdelavo protetičnih pripomočkov, saj zadostujejo vsem potrebnim kriterijem v ortotiki in protetiki. Če je ležišče izdelano iz naravnih materialov kot so kenaf, bambus, juta in ostala naravna vlakna, je okolju prijazno in hkrati povzroča človeškemu telesu manj alergij, povezanih z umetno izdelanimi materiali. Introduction: Plastic and polymer composites with carbon fibers are often used to make orthoses and prostheses. Nowadays, however, due to the increasing demand for environmentally friendly materials and the desire to reduce the price of composite materials, researchers have begun to pay attention to natural fiber and matrix of natural origin. Purpose: The main purpose of the thesis was to identify and study the natural materials used in the manufacture of orthoses and prostheses. Methods: A descriptive method for searching home and foreign internet literature was used to write the thesis. The collected literature, which is in English, was searched in various databases such as Science Direct, PubMed, Google Scholar and Cochrane Library. Results: The use of materials from natural resources has increased worldwide due to environmental considerations and economic benefits, compared to the use of non-renewable resources. The advantages of natural fiber composites are greater elasticity, biodegradability, environmental friendliness and cost benefits, but they also exhibit great strength, stiffness and corrosion resistance Discussion and conclusion: On the basis of studies, we found that natural fibers are suitable for the production of prosthetic devices, as they meet all the requirements needed in orthotics and prosthetics. If the bed is made of natural materials, such as kenaf, bamboo, jute and other natural fibers, it is environmentally friendly and at the same time causes fewer artificially produced materials connected allergies to the human body.

ilustraciones, fotografías, gráficas, planos En esta investigación se determinó la influencia de reforzar externamente vigas de concreto sometidas a flexión empleando un compuesto hecho con matriz epóxica y fibras de fique. Para esto se caracterizó mecánicamente la fibra de fique antes y después de ser sometida a un tratamiento alcalino. El tratamiento alcalino usado fue a base de hidróxido de sodio (NaOH), logrando con este procedimiento mejorar las propiedades mecánicas de la fibra de fique. Posteriormente, se caracterizó mecánicamente el tejido de fique, previamente sometido al tratamiento alcalino. Se fabricó una matriz epóxica, la cual fue sometida a ensayos de tensión para determinar sus propiedades mecánicas. Para la fabricación del compuesto epóxico/fique (EF) se emplearon dos tipos de tejidos, un tejido tupido (D) y un tejido ralo (MD), obteniendo mayores prestaciones mecánicas al emplear el tejido tupido, con un contenido de fibras de fique del 10 %, como fracción de peso. Se fabricaron vigas de concreto empleando dos tipos de resistencia a la compresión, una de 17 MPa y la otra de 24 MPa. Estas vigas fueron reforzadas externamente, en la cara inferior del elemento, empleando el compuesto EF. Posteriormente, fueron sometidas al ensayo a flexión de cuatro puntos para evaluar el comportamiento de las vigas reforzadas ante esfuerzos de flexión. Al reforzar estas vigas con el compuesto EF de observó que la resistencia a la flexión aumentó entre un 15 y 20 % para vigas con concreto de 17 MPa y un 10 % para las vigas hechas con concreto de 24 MPa. El módulo de elasticidad de las vigas reforzadas aumentó hasta un 20 % y las deflexiones se redujeron. Se propusieron unas expresiones teóricas para ser comparadas con los resultados obtenidos en el laboratorio, logrando precisión en las ecuaciones determinadas para la evaluación de esfuerzos en vigas compuestas, y una buena aproximación en la ecuación definida para la evaluación del momento nominal de la viga reforzada externamente con EF. (Texto tomado de la fuente) In this research, the influence of externally reinforcing concrete beams subjected to bending using a composite made with an epoxy matrix and fique fibers was determined. For this, the fique fiber was mechanically characterized before and after being subjected to an alkaline treatment. The alkaline treatment used was based on sodium hydroxide (NaOH), achieving with this procedure to improve the mechanical properties of fique fiber. Subsequently, the fique fabric, previously subjected to alkaline treatment, was mechanically characterized. An epoxy matrix was manufactured, which was subjected to stress tests to determine its mechanical properties. For the manufacture of the epoxy/fique composite (EF) two types of fabrics were used, a dense fabric (D) and a sparse fabric (MD), obtaining greater mechanical performance when using the dense fabric, with a fique fiber content of 10%, as a weight fraction. Concrete beams were manufactured using two types of compressive strength, one of 17 MPa and the other of 24 MPa. These beams were externally reinforced, on the lower face of the element, using the EF compound. Subsequently, they were subjected to the four-point bending test to evaluate the behavior of the reinforced beams under bending stresses. When reinforcing these beams with the EF compound, it was observed that the flexural strength increased between 15 and 20% for beams with 17 MPa concrete and 10% for beams made with 24 MPa concrete. The elastic modulus of the reinforced beams increased up to 20% and deflections were reduced. Some theoretical expressions were proposed to be compared with the results obtained in the laboratory, achieving precision in the equations determined for the evaluation of forces in composite beams, and a good approximation in the equation defined for the evaluation of the nominal moment of the externally reinforced beam. with EF. Maestría Magíster en Ingeniería - Estructuras Materiales de construcción para estructuras

Natural fibers are increasingly being used to make nonwoven fabrics, substituting synthetic materials for environmental and economic reasons. In this study, a series of needle-punched nonwoven fabrics were made by extracting fibers from coffee husks and blending them with a proportion of spinning waste consisting of cotton fibers and another five different natural fibers. This work investigates the coefficient of sound absorption, thermal conductivity, areal density, thickness, and air permeability. Overall, the sound absorption properties of the produced nonwoven fabric depend on the blend proportion and the number of layers. The results from the fabric containing nettle and banana fibers demonstrate a much-improved sound absorption coefficient. These results have been compared with those of commercially available nonwoven fabrics that are manufactured from polyester and polyurethane foam. The thermal conductivities of the fabrics made with nettle and coir were the highest and lowest, respectively. This is because of the fiber linear density, but all in all, fibers extracted from coffee husks show significantly promising potential for scaling up to replace existing synthetic fibers.

Houses in the operational stage consume around 40% of the world’s energy, and most of it is consumed by air conditioning. This generates several problems, especially in cities, where biomass combustion is the most widely used form of heating. For this reason, environmental regulation works in parallel with energy efficiency, where efficient and low-impact thermal insulating materials are key to reduce the energy demand and fuel consumption to generate comfort in dwellings. This work considers the valorization of wheat straw from the Araucanía region of Chile, to develop a prototype for a thermal insulating material applied through the blowing technique. The results show the insulation potential of the fiber, which, in post-chopping conditions and at an average density of 80 [kg/m3], has thermal conductivity of 0.034 [W/mK]. This value is much better than that of glass wool and other inorganic materials sold in the Chilean market. In addition, the developed material can be incorporated into partitions using the blowing technique, improving the execution time for the thermal insulation section. Finally, it is indicated that a good option to install a processing plant is in the central valley of the region, specifically in the communes of Victoria and Perquenco.

Namen magistrskega dela z naslovom Taktilnost tkanine z zankasto površino, je v prvi vrsti raziskati pomen dotika in njegovo mesto v svetu umetnosti. Teza, ki je raziskana v prvem delu magistrskega dela, je, da je vsa umetnost na nek način nedotakljiva in s tem opazovalcu nikoli zares ne pusti blizu, če je ta ne more doživeti z vsemi čutili. Tako je tudi v tekstilni umetnosti, ker pa je tekstil tako močan element v našem vsakdanjem življenju, se je dotiku le-tega praktično nemogoče izogniti. Eno izmed reliefno površinskih struktur tekstila je mogoče izdelati s tehniko tkanja zankaste površine. To je starodavna tradicionalna sardinska obrtna dejavnost, imenovana tehnika ''pibiones'' in je le redko ohranjena. V magistrskem delu predstavlja osrednjo tehniko, ki je bila uporabljena za ročno izdelane tkanine. V drugem delu magistrskega dela je prikazan celoten proces oblikovanja in ročnega tkanja več manjših vzorčnih tkanin, oblikovanja vzorcev in izbire preje za tkanje. Izbrane preje so bile iz naravnih in recikliranih surovin. Z združevanjem vsega naštetega so nastale tri unikatne ročno izdelane tkanine, ki poleg vizualno privlačne podobe vabijo, dopuščajo in spodbujajo dotik. The purpose of the Master's work, entitled Tactility of a fabric with a looped weaved surface, is primarily to investigate the meaning of touch and its place in the world of art. The thesis, which is explored in the first part of the master's work, is that all art is in some way untouchable and thus never really leaves the viewer close, if he cannot experience it with all his senses. This is also the case in textile art, but because textiles are such a strong element in our daily lives, it is practically impossible to avoid touching them. One of the relief surface structures of textiles can be produced using the technique of weaving a looped surface. This is an ancient traditional Sardinian craft called the "pibiones" technique, which is rarely preserved. In his master's thesis, he presents the central technique that was used to produce the final woven pieces. In the second part of the master's work, the entire process of designing and manufacturing woven pieces is shown, which included many smaller test pieces, pattern design and the selection of fibers for weaving. Fibers were selected based on natural origin or recycled material. By combining all of the above, three woven pieces were created that, in addition to a visually attractive image, invite, allow and encourage touch.

This article presents the results of an acoustic characterization of fibers obtained from Posidonia Balls (scientific name: Aegagropiles), produced by a marine plant (Posidonia oceanica) that is widespread in the Mediterranean Sea and can be found on beaches in large quantities, particularly following storm surges. The aim of this research is to evaluate the possible use of these fibers as eco-sustainable sound-absorbing materials and to define an acoustic model for the optimization of sound-absorbing panels made from these fibers. Experimental tests were conducted to measure airflow resistivity and sound absorption for different densities of loose fiber samples. From these experimental tests, the five physical parameters of the Johnson-Champoux-Allard model were calculated to obtain an analytical formulation of the acoustic behavior of the fibers depending on their density. To the author’s knowledge, this is the first time that an article has been published on acoustic data relating to the sound-absorbing performance of loose Posidonia oceanica fibers and that an analytical model has been presented that allows for the acoustical design of panels of different thicknesses and densities made with this material. An interesting aspect of this material is that the lignin fibers are ready for acoustic application due to the natural cleaning process of the waves and salt water. Furthermore, the methodology consists of a hybrid method between the experimental characterization of some parameters (i.e., different densities) and the numerical inversion of the acoustic data for other parameters. This is an effective solution that has rarely been adopted in other studies on sustainable materials.

The use of natural fibers including abaca has increased because of its advantages such as lightweight, low price, life-cycle superiority, and substi tute for synthetic fibers. This paper gives an insight into the effect of three different treatments on abaca fibers: hornification, NaOH 3% concentration solution, and a coating of silica fume with natural latex into cementitious composites; fibers have been characterized before and after through SEM, XRD, FT-IR, TGA, and tensile tests to analyze structural and chemical changes. Cementitious composites through setting time and flexural strength (7, 14, 28 days) were analyzed for determining the optimum treatment and, after ward, the best dosage and length. It was found that HS treatment with 30 mm and 0.2% dosage showed 8.2 MPa in terms of flexural strength, Universidad Católica de Santiago de Guayaquil under Grant Cod. Pre 515, cod Int. 326

In this paper, the effect of integration of natural fibers in UD carbon fiber is studied. The integration of natural fibers in carbon fiber is made via intra fiber hybridization. Natural fiber hybrid composite samples were prepared for Mode I and Mode II fracture tests. XRD analysis was done for the chosen natural fibres to know the crystallinity index and then compared with Carbon and Glass fibres. The fracture test experimental results, revealed that the effect of Jute fiber integration in UD Carbon epoxy composite was found significant in getting relatively good Mode I and II fracture toughness at the crack initiation without losing its stiffness. In addition to this Kenaf Carbon epoxy composite indicated better crack suppression with 30% higher propagation toughness values as compared other hybrid combinations and pristine composites. It is observed that integration of jute fibers in UD carbon epoxy composites was significant in achieving good mode I and mode II fracture toughness at the crack initiation without losing its stiffness and also kenaf carbon epoxy composites indicated better crack suppression with 30% higher propagation toughness as compared to other hybrid combinations used.

The use of bio-based matrices together with natural fibers as reinforcement is a strategy for obtaining materials with competitive mechanical properties, costs, and environmental impacts. However, bio-based matrices, unknown by the industry, can be a market entry barrier. The use of bio-polyethylene, which has properties similar to polyethylene, can overcome that barrier. In this study, composites reinforced with abaca fibers used as reinforcement for bio-polyethylene and high density polyethylene are prepared and tensile tested. A micromechanics analysis is deployed to measure the contributions of the matrices and reinforcements and to measure the evolution of these contributions regarding AF content and matrix nature. The results show that the mechanical properties of the composites with bio-polyethylene as a matrix were slightly higher than those of the composites with polyethylene as a matrix. It was also found that the contribution of the fibers to the Young’s moduli of the composites was susceptible to the percentage of reinforcement and the nature of the matrices. The results show that it is possible to obtain fully bio-based composites with mechanical properties similar to those of partially bio-based polyolefin or even some forms of glass fiber-reinforced polyolefin.

In this work have been evaluated adhesion of coconut and banana fibers on several treatment conditions and using two polymeric matrix. Fibers were extracted from banana pseudostem and coconut esocarp, which were dried at a temperature of 40°C and 90°C, determining how the drying temperature influences the mechanical properties. Choosing 40°C for banana fibers and 90°C for coconut fibers as the best temperature, these sets of fibers were treated with alkali and various properties were compared using characterization techniques such as tension tests, scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and Fourier transform infrared spectroscopy (FTIR). Simply dried and INFORME FINAL DEL TRABAJO DE INVESTIGACIÓN CONVENCIONAL Comité de Acreditación y Currículo Facultad de Ingenierías por una universidad con calidad, moderna e incluyente Carrera 6ª. No. 76-103 Montería NIT. 891080031-3 - Teléfono: 7860300 - 7860920 www.unicordoba.edu.co mercerized fibers were embedded in polymeric matrices to determine the influence of fiber treatment on adhesion with polylactic acid (PLA) and unsaturated polyester resin and to obtain manufacturing parameters to improve the properties of natural fiber-reinforced composites using 3D printing and resin transfer molding (RTM) processes. Using the PullOut fiber extraction test, it was possible to prove that mercerizing improves the interfacial adhesion with the abovementioned matrices. RESUMEN 9 ABSTRACT 10 1 INTRODUCCIÓN 10 2 OBJETIVOS 13 2.1 OBJETIVO GENERAL 13 2.2 OBJETIVOS ESPECÍFICOS 13 3 REVISIÓN BIBLIOGRÁFICA 13 4 ESTADO DEL ARTE 17 5 MATERIALES Y MÉTODOS 19 5.1 RECOLECCIÓN DE LA MATERIA PRIMA 19 5.2 EXTRACCIÓN DE FIBRA NATURALES 20 5.3 TRATAMIENTO CON ÁLCALIS O MERCERIZADO 22 5.4 TRATAMIENTO DE SECADO DE FIBRAS 23 5.5 CARACTERIZACIÓN MECÁNICA DE LAS FIBRAS POR ENSAYO DE TENSIÓN 24 5.5.1 Montaje de fibra en plantilla de cartón paja 24 5.5.2 Medición de diámetros de las fibras de plátano y coco mediante microscopia óptica 26 5.5.3 Acondicionamiento de las fibras para ensayos de tensión 28 5.5.4 Ensayo de tensión de fibras de plátano y coco 28 5.6 ANÁLISIS POR ESPECTROSCOPIA INFRARROJA POR TRANSFORMADA DE FOURIER 30 5.7 ANÁLISIS MORFOLÓGICO POR MICROSCOPIA ELECTRÓNICA DE BARRIDO (SEM) 32 5.8 ANÁLISIS TERMOGRAVIMÉTRICO (TGA) 35 5.9 CALORIMETRÍA DIFERENCIAL DE BARRIDO (DSC) 36 5.10 ENSAYO DE EXTRACCIÓN DE FIBRA (PULL-OUT) 37 5.10.1 Preparación probetas de Pull-Out con matriz termofija de resina de poliéster insaturada 38 5.10.2 Preparación probetas de Pull-Out con matriz termoplástica de ácido poliláctico (PLA) 39 5.10.3 Montaje de probetas de Pull-Out en láminas de cartón paja 40 5.10.4 Ensayo de extracción de fibra Pull-Out 41 6 RESULTADOS Y DISCUSIONES 42 6.1 CARACTERIZACIÓN MECÁNICA DE LAS FIBRAS POR ENSAYO DE TENSIÓN 42 6.1.1 Medición de diámetros de las fibras de plátano y de coco mediante microscopia óptica 43 6.1.2 Propiedades mecánicas de las fibras de plátano y de coco en función del tratamiento 44 6.2 ANÁLISIS POR ESPECTROSCOPIA INFRARROJA POR TRANSFORMADA DE FOURIER 47 6.3 ANÁLISIS MORFOLÓGICO POR MICROSCOPIA ELECTRÓNICA DE BARRIDO 53 6.4 ANÁLISIS TERMOGRAVIMÉTRICO (TGA) 59 6.5 CALORIMETRÍA DIFERENCIAL DE BARRIDO (DSC) 67 6.6 ENSAYO DE EXTRACCIÓN DE FIBRA (PULL-OUT) 68 7 CONCLUSIONES 72 8 RECOMENDACIONES 72 9 BIBLIOGRAFÍA 72 En este trabajo se evaluó la adhesión de fibras de plátano y coco bajo diversas condiciones, en dos polímeros diferentes. Se extrajeron fibras del pseudotallo del plátano y del mesocarpio del coco, que se secaron a una temperatura de 40°C y 90°C para determinar cómo influye la temperatura de secado en las propiedades mecánicas. Eligiendo 40°C para las fibras de plátano y 90°C para las de coco como temperatura óptima, estos conjuntos de fibras se trataron con álcali y se compararon diversas propiedades mediante técnicas de caracterización como ensayos de tensión, microscopía electrónica de barrido (SEM), análisis termogravimétrico (TGA) y espectroscopia infrarroja por transformada de Fourier (FTIR). Se embebieron fibras simplemente secadas y mercerizadas en matrices poliméricas para determinar la influencia del tratamiento de las fibras en la adhesión con ácido poliláctico (PLA) y resina de poliéster insaturado y obtener parámetros de fabricación para mejorar las propiedades de los compuestos reforzados con fibras naturales mediante procesos de impresión 3D y moldeo por transferencia de resina (RTM). Mediante el ensayo de extracción de fibras Pull-Out, se pudo comprobar que el mercerizado mejora la adhesión interfacial con las matrices mencionadas. Pregrado Ingeniero(a) Mecánico(a) Trabajos de Investigación y/o Extensión

International audience; In this study, the goal was to compatibilize flax natural fibers (which are inherently polar) with mostly dispersive polymers, while proposing a way to recover greenhouse gases or refrigerants such as CF4 or C2F5H. Such gases exhibit a high global warming potentials (GWPs) and their recovery at the end of their lifecycle is difficult. Therefore, these two representative problematic gases were used as plasma precursor to graft fluorine atoms onto the flax fiber surface. Chemical investigation (FT-IR, 19F NMR and XPS spectroscopies), demonstrates the covalent grafting of fluorine atoms at the fiber surface, that opens the route of tailoring the surface chemistry of flax fibers. These modifications induced a decrease of the fiber polarity, which allows the treated fibers to become perfectly compatible with mostly dispersive polymer. Moreover, both mechanical properties and fluorine release during fibers combustion were investigated and any negative impact was evidenced. Therefore, thanks to the plasma fluorination, the gap between the surface energies of the fibers and mostly dispersive polymer matrix was reduced improving the wettability of the fibers through an eco-friendly way. This phenomenon promising an improvement in the mechanical performance of eco-composites reinforced with these fluorinated fibers.

Flax fibers are widely used as the strongest natural fibers in composite parts with advanced structures. Due to their excellent mechanical properties and recyclability, they have attracted more attention from the aviation and automotive industries, etc. These composite parts are usually obtained by preforming reinforcements or prepregs at high temperatures, and their mechanical behaviors are greatly affected by temperature variations. To improve the understanding of the mechanical properties of flax fiber materials, especially for the braided fabric with non-orthogonal structures, uniaxial tensile tests at different temperatures and tensile speeds were conducted on hollow tubular braided fabrics. The thermomechanical properties of Flax/Polyamide12 (PA12) prepregs were analyzed. The results show that temperature and tensile speed have obvious effects on the strength and shear stiffness of tubular fabrics. The strength and shear stiffness of the fabric decreases as the ambient temperature increases. Meanwhile, the strength of the fabric can also be improved by appropriately increasing the tensile speed. In addition, according to the experimental results, a theoretical model is established to describe the shear angle on the smallest circumference of the fabric, which provides a theoretical basis for the subsequent simulation process. The test results can provide a reference for the manufacture of flax fiber-reinforced composites with tubular structures.

Natural fiber-reinforced composites can contribute to reducing carbon footprint goals due to their ability to reduce overall product weight, bio-diverse feedstocks, and recyclability potential. In this work, natural fiber-based composites containing the reinforcement of coconut husk and bagasse fiber with calcium carbonate (CaCO3) ingredients were prepared and analyzed. The composites were analyzed for mechanical, thermomechanical, and morphological properties. The reinforcements were chemically functionalized using 5% w/v NaOH to enhance their interactions with the epoxy resins. The chemical functionalization created perforation on the fiber surface, improving the interlocking of fibres with the resin material and strengthening the mechanical performance of the composite. The composites developed using modified reinforcement treatment resulted in increased tensile strength (64.8%) and flexural strength (70%). The reinforcement treatment influenced the hydrophilicity, and the water absorption of treated composites was reduced more than five times compared to the unmodified composites. Scanning electron microscopy revealed morphological changes due to fiber modification, the underlaying mechanism of fiber contraction, and enhanced fiber matrix interface interlocking and adhesion strengthening. Thermal analysis confirmed that alkali treatment improves the crystallinity of the fiber and thereto the degradation temperature of treated fiber composites (both bagasse and coconut husk), which is 375.27 °C, the highest amongst the developed hybrid composites.

The production of cement increases every year, which leads to the emission of dust/gas/ particulate matter. The emission of unfiltered dust would create a significant environmental impact. Hence, it is the responsibility of industries to control the emission of dust. Air filters and electrostatic precipitators (ESP) play a significant role in controlling pollutants. Synthetic filter media which are dangerous to our environment are widely used in most industries. The disposal of synthetic filters is an arduous task as the biodegradability of synthetic materials is poor. Hence, it is essential to develop an eco-friendly air filter material. In this paper, a new type of bag filter was designed by using natural sisal fiber as filtering media. The biodegradability of sisal fiber is better than the synthetic polyester media and also sisal fiber is less expensive. The natural fibers were coated with zinc oxide and iron oxide nanoparticles to improve the dust adsorption rate. Various tests were conducted as per standards to validate the performance of the filler media. The results were impressive. Hence, the proposed sisal fiber-based filter media can be used in cement industries for dust adsorption to minimize the environmental impact.

The growing demand for plant fiber-reinforced composites offers new opportunities to compete against glass fiber (GF)-reinforced composites, but their performance must be assessed, revised, and improved as much as possible. This work reports on the production and the flexural strength of composites from polypropylene (PP) and hemp strands (20–50 wt.%), using maleic anhydride-grafted PP (MAPP) as a compatibilizer. A computational assessment of the reaction between cellulose and MAPP suggested the formation of only one ester bond per maleic anhydride unit as the most stable product. We determined the most favorable MAPP dosage to be 0.06 g per gram of fiber. The maximum enhancement in flexural strength that was attained with this proportion of MAPP was 148%, corresponding to the maximum fiber load. The modified rule of mixtures and the assumption of similar coupling factors for tensile and flexural strength allowed us to estimate the intrinsic flexural strength of hemp strands as 953 ± 116 MPa. While falling short of the values for sized GF (2415 MPa), the reinforcement efficiency parameter of the natural fibers (0.209) was found to be higher than that of GF (0.045).

In recent years, one of the main challenges is to improve the mechanical performance of bio-composites to be used as structural parts for the construction, automotive, and aviation sector. This paper may contribute to developing durable structural bio-composite parts with starch addition. The mechanical properties of bio-composites reinforced by eucalyptus or pine fibers (48 wt %) compound with Cationic Starch (48 wt %) and Carboxymethyl cellulose (CMC) (4 wt %) were determined. The production method was a combination of molded pulp, extrusion, and compression molding production techniques. To see the effect of adding starch to bio-composites and different production methods, the mechanical performance of these natural fibers produced by the conventional molded pulp production method (without any additives) was also found and compared with the composite samples. Composite samples indicate significantly better tensile, flexural, and compressive values, at least four times, compared with the molded pulp samples. On the other hand, the molded pulp samples had more than 2 times better impact characteristics against composites. Using molded pulp technic in composite production (investigated in the study) is a new idea and may give some opportunities with its serial production compatibility and geometry freeness, to the industry.

Mención Internacional en el título de doctor Industrial materials are constantly evolving to enhance the specifications of the final product, reduce manufacturing costs, or comply with new regulations established by authorities that force the usage of recyclable and reusable materials to reduce the creation of solid waste. In recent years, research into new biodegradable materials has experienced a remarkable expansion thanks to the increasing use of natural resources in industries, such as natural fibers and bioplastics. Moreover, such green composites are usually sourced in developing countries. If natural fibers can finally extend to more industrial areas, it may be a benign stimulus to their economic development. This thesis mainly contributes to analyzing and modeling energy-absorbent structures made of biodegradable composites and studying their mechanical behavior under low-velocity impact tests and buckling loads. Four types of green composite bumper beams with different cross-sections were manufactured, tested, and compared. Each type of bumper beam was tested in a drop-weight tower to evaluate the impact performance, and the post-impact behavior was studied through a quasi-static bending test. The analysis of the impact behavior revealed that the higher the roundness of the cross-section, the best the impact performance. On the other hand, the intermediate design bumper beam showed the best after-impact residual mechanical properties. Thus, the results indicate that the choice of the cross-section depends on whether the goal is to maximize the impact performance or the post-impact residual properties of the bumper structure. A numerical model was developed in Abaqus/Explicit to reproduce the impact performance of the four green composite bumper beams and to analyze the damage evolution and the energy-absorption mechanisms of the structures as a function of the impact energy and cross-section roundness. The numerical results showed excellent agreement with the experimental data. The model could predict the damage behavior of the structure from localized damage to complete failure under different impact energies. Moreover, the damage evolution showed that the delamination appears initially in the section corners and then spreads further. It implies that delaminations are more prone to propagate through the entire cross-section and more prematurely for rounder types. The squarest cross-section was the bumper beam with the highest energy-absorption capability, and the roundest one presented the lowest energy-absorption capability. In this doctoral dissertation, the nonlinear elastic constitutive law, modified Ludwick formulation, was experimentally validated for the first time. The buckling response of slender columns made of flax/PLA green composites was studied through three approaches. As a result, a reasonable agreement was found between the experimental results, numerical predictions, and theoretical estimations. Then, the modified Ludwick’s law was considered experimentally validated as a theoretical method to predict the critical buckling load of nonlinear elastic columns. However, the numerical approach using the Marlow hyperelastic model needed to show more accuracy when the nonlinearity of the material was relatively large. Therefore, validating the theoretical results with the numerical model should always be considered carefully. Lastly, the influence of the column cross-section was also analyzed. The FEM model could exactly reproduce the buckling mode of all the cases, but the prediction errors of critical buckling load for columns with low slenderness ratios were considerable. On the other hand, columns with a slenderness ratio of about 170 were the limit of application of the modified Ludwick’s law to predict the critical buckling load of nonlinear elastic columns with open cross-sections, and columns with a ratio between 48 and 52 were out of prediction limits. Generally, the numerical and theoretical models underestimated the scattering effects of the predictions because the models did not consider more experimental variables. Especially in the analytical model, lateral torsional buckling should be included in the formulation to predict the buckling load of the nonlinear elastic column correctly. Los materiales industriales evolucionan constantemente para mejorar las especificaciones del producto final, reducir los costos de fabricación o cumplir con las nuevas regulaciones establecidas por las autoridades que obligan al uso de materiales reciclables y reutilizables para reducir la generación de desechos sólidos. En los últimos años, la investigación de nuevos materiales biodegradables ha experimentado una notable expansión gracias al creciente uso de recursos naturales en las industrias, como las fibras naturales y los bioplásticos. Además, estos materiales compuestos ecológicos suelen obtenerse en países en desarrollo. Si las fibras naturales finalmente pueden extenderse a más áreas industriales, puede ser un estímulo benigno para su desarrollo económico. Esta tesis contribuye principalmente al análisis y modelado de estructuras absorbentes de energía fabricadas con materiales compuestos biodegradables y al estudio de su comportamiento mecánico bajo ensayos de impacto a baja velocidad y su resistencia a pandeo. Se fabricaron, ensayaron y compararon cuatro tipos de vigas de parachoques de materiales compuestos verdes con diferentes secciones transversales. Cada tipo de viga parachoques se probó en una torre de caída de peso para evaluar el comportamiento frente a impacto, y el comportamiento después de impacto se estudió a través de ensayos de flexión cuasi-estática. El análisis del comportamiento frente a impacto reveló que cuanto mayor es la redondez de la sección transversal, mejor es el rendimiento. Por otro lado, la viga parachoques de diseño intermedio mostró las mejores propiedades mecánicas residuales después del impacto. Por lo tanto, los resultados indican que la elección de la sección transversal depende de si el objetivo es maximizar el comportamiento frente a impacto o las propiedades residuales después de impacto. Se desarrolló un modelo numérico en Abaqus/Explicit para reproducir el impacto de las cuatro vigas de parachoques de materiales compuestos biodegradables y para analizar la evolución del daño y los mecanismos de absorción de energía de las estructuras en función de la energía de impacto y la redondez de la sección transversal. Los resultados numéricos mostraron una excelente concordancia con los datos experimentales. El modelo podría predecir el comportamiento de la estructura desde daño localizado hasta rotura completa bajo diferentes energías de impacto. Además, la evolución del daño mostró que la delaminación se manifiesta inicialmente en las esquinas de la sección y luego se extiende a partir de esos puntos. Esto implica que las delaminaciones son más propensas a propagarse a través de toda la sección transversal y más prematuramente para los tipos más redondos. La sección transversal más cuadrada fue la viga parachoques con la capacidad de absorción de energía más alta, y la más redonda presentó la capacidad de absorción de energía más baja. En esta tesis doctoral, se validó experimentalmente por primera vez la ley constitutiva elástica no lineal, formulación de Ludwick modificada. La respuesta de pandeo de columnas esbeltas hechas de materiales compuestos biodegradables de lino/PLA se estudió a través de tres enfoques. Como resultado, se encontró una concordancia razonable entre los resultados experimentales, las predicciones numéricas y las estimaciones teóricas. Por lo tanto, la ley de Ludwick modificada se consideró validada experimentalmente como un método teórico para predecir la carga crítica de pandeo de columnas elásticas no lineales. Sin embargo, el enfoque numérico que usaba el modelo hiperelástico de Marlow perdía precisión cuando la no linealidad del material era relativamente grande. Por lo tanto, la validación de los resultados teóricos con modelos numéricos siempre debe considerarse cuidadosamente. Por último, también se analizó la influencia de la sección transversal de la columna. El modelo numérico pudo reproducir exactamente el modo de pandeo de todos los casos, pero los errores de predicción de la carga crítica de pandeo para columnas con bajas relaciones de esbeltez fueron considerables. Por otro lado, las columnas con una relación de esbeltez de alrededor de 170 fueron el límite de aplicación de la ley de Ludwick modificada para predecir la carga crítica de pandeo de columnas elásticas no lineales con secciones transversales abiertas, y las columnas con una relación entre 48 y 52 quedaron fuera de los límites de la predicción. Generalmente, los modelos numéricos y teóricos subestimaron los efectos de dispersión de las predicciones porque los modelos no consideraron todas las variables experimentales. Especialmente en el modelo analítico, el pandeo lateral-torsional debe ser incluido en la formulación para poder predecir correctamente la carga de pandeo de la columna elástica no lineal. Programa de Doctorado en Ingeniería Mecánica y de Organización Industrial por la Universidad Carlos III de Madrid Presidente: Ramón Eulalio Zaera Polo.- Secretario: Mario Domingo Monzón Verona.- Vocal: Samuel Charca Mamani

Green materials have received great interest in wide industrial applications due to their desired properties. However, the reinforcing conditions have a significant impact on how they perform in their final use. The current study intends to statistically examine the effects of three key parameters on the average tensile strength of polypropylene composites. These factors included the type of fiber, the chemical treatment, and the fiber's weight percentage. The fibers were hemp and sisal, and the weight percentages were 10, 20, and 30. While some of them received sodium hydroxide (NaOH) treatment, the rest were left untreated. The main effect and the interaction effect were both examined using the analysis of variance (ANOVA). The findings demonstrated that, on average, the weight percentage had no tangible effect on the tensile strength of polypropylene (PP) composites. Additionally, the performance of sisal and hemp composites was unaffected by treatment. The strength, however, is significantly influenced by the type of fiber. The investigation also showed that there was little difference between untreated hemp and untreated sisal in terms of tensile strength.

Technological finishing processes are carried out mainly by chemical, physico-chemical effects on fibrous materials. The process of dyeing fabrics from cotton-bamboo fibers with active dyes was carried out. The influence of the components of the dye bath on the quality of dyeing and on the strength of the fabric was studied.

The tribological behavior of new green friction materials with rice husk (RH) and rice husk ash (RHA) is dis-cussed in the current paper. Two formulations developed, one with 6% RH and one with 6% RHA, were compared with a reference formulation with alumina under the AK Master test, through a braking tribometer. Formulation with RHA showed tribological performance equal to or better than the reference material, especially in high temperature applications where the RHA particles assisted in the building of the contact plateaus. Adding RH reduced the abrasive action of the composite, allowing the formation of a more homogeneous tribofilm on the disc than in the other formulations.

Concerned about the environmental and economic impact, composite materials are increasingly used in the construction sector. Indeed, the use of plant fibers as reinforcement in construction materials have been the subject of several researches in recent years; the main motivation is the weight gain combined with high mechanical characteristics. The objective of this research concerns the study of the physicomechanical properties of composite materials with cement and clay matrices reinforced with Alfa and Diss fibers with dimensions ranging from 2 to 8 cm. This involves evaluating the performance of these materials according to the formulation, for a volume ratio (Alfa or Diss / Matrix fibers equal to 4), using dry fibers and pre-wetted fibers. The study of the mechanical properties showed a drop of the performance for both compression and bending strength compared to the reference material without adding fibers (cement or clay paste). It should be noted that the best mechanical performance is obtained for the case of composites materials with cementitious matrix with pre-wetted fibers. On the other hand, in the case of composites with clayey matrices, pre-wetting does not improve the mechanical characteristics. It is also noted that the best dimensions of fibers which improve the mechanical characteristics in bending are generally 6 cm for composites with a clay matrix and between 2 and 4 cm for cementitious composites. In all cases, the fibers in composite materials with cement or clay matrix create a bridging effect, making it possible to limit the progression of cracks during loading. This phenomenon gives to the various composite materials a ductile behavior.

The compatibility between poly(lactic acid) (PLA) and natural fibers to develop bio-sourced, recyclable, and biodegradable composites remains a commonplace issue. This work highlights that, at least in the case of hemp, pulping and bleaching towards delignified short fibers attained remarkable improvements over untreated hemp strands. This approach differs from usual proposals of chemically modifying hydroxyl groups. Soda-bleached hemp fibers (SBHFs) granted a relatively large bonding surface area and a satisfactory quality of the interphase, even in the absence of any dispersant or compatibilizer. To attain satisfactory dispersion, the matrix and the fibers were subjected to kinetic mixing and to a moderately intensified extrusion process. Then, dog-bone specimens were prepared by injection molding. Up to a fiber content of 30 wt.%, the tensile strength increased linearly with the volume fraction of the dispersed phase. It reached a maximum value of 77.8 MPa, signifying a relative enhancement of about 52%. In comparison, the tensile strength for PLA/hemp strands was 55.7 MPa. Thence, based on the modified rule of mixtures and the Kelly & Tyson modified equation, we analyzed this performance at the level of the constituent materials. The interfacial shear strength (over 28 MPa) and other micromechanical parameters were computed. Overall, this biocomposite was found to outperform a polypropylene/sized glass fiber composite (without coupling agent) in terms of tensile strength, while fulfilling the principles of green chemistry.

The aim of the present study was to investigate the effects of fiber content and then silane treatment on the mechanical performance of the natural fiber composites of recycled acrylonitrile–butadiene–styrene (ABS) provided by the automotive sector. Wood and palmyra fibers were used as fillers in 10% and 20% fiber content composites. The fibers were treated with N-(2-Aminoethyl)-3-aminopropyltrimethoxysilane to improve the interfacial adhesion between fibers and polymer matrices. The mechanical properties of the composites were determined by tensile and impact tests. Morphological analysis was later performed using a scanning electron microscope (SEM). According to the experiment results, the tensile and impact strength of both wood and palmyra fibers increase after silane treatment. However, for the low-wood-fiber-content composite, the tensile and impact strength decrease after silane treatment due to the presence of an excess amount of silane relative to fiber content. The addition of wood and palmyra fibers significantly improved the tensile modulus of composite material and further increases slightly after silane treatment. Finally, SEM analysis shows a homogenous mix of fibers and polymer matrices with fewer voids after silane treatment, thereby improving interfacial adhesion.

The annual worldwide production of coffee exceeds 10 million tons, and more than 90% of this production is waste, including the husk. On the other hand, plastic consumption increases every year, and sustainable alternatives are necessary to decrease it. This work arises to solve these two problems, and seeks to produce products at an industrial level from polyethylene/coffee husk eco-composites. Both Low Density Polyethylene and High Density Polyethylene were used, and the amounts of coffee husk added as filler were 20 and 40 wt%. The composites were characterized by different morphological, thermal and mechanical techniques. Scanning Electron Microscopy images showed husk particles embedded in the polymer matrix, but with some gaps between the polymer and the filler, because no compatibilizer agent was used. The addition of large amounts of natural filler negatively affected the tensile strength and elongation at break, but increases eco-composites crystallinity, and hence, their Young modulus and hardness. The industrial applicability of the eco-composites was verified through the production of five different consumer products by extrusion and injection processes, using mixtures with 40 wt% coffee husks. All products were obtained without significant defects. If only 3.25 wt% of the polyethylene products produced each year in Colombia did so with the eco-composites developed in this work, all the coffee husk produced in the country would be used, and the emission of about 5.390 million m3 of greenhouse gases would be avoided.

Mechanical properties are very important properties of woven fabric, it affects on the load a textile material can withstand during use. Recently, attention has been increased to use of renewable resources especially of plant origin keeping in view the ecological concerns. Banana fibre is biodegradable and has no negative effect on environment and thus can be categorized as eco-friendly fibre. This paper is aimed at understanding the mechanical properties of (banana/cotton) woven fabrics based on three different banana fibre ratios in weft direction (50% banana: 50% cotton, 33.4% banana: 66.6% cotton & 25% banana: 75% cotton) respectively. With three weave structures (plain 1/1, twill 2/2 and satin 4) differ from each other in the float length.Mechanical Properties of produced samples were investigated according to ASTM standard methods including tensile strength, elongation, tearing and abrasion resistance. The results were evaluated using statistical analysis and it is noticed that there is a direct proportional relationship between increasing the banana fibre ratio and the tensile strength in warp direction and elongation in both directions, whilst there is an inverse relationship between the ratio of banana fibre and the tensile strength in weft direction, tear strength in weft direction and abrasion resistance.The weave structure plain1/1 has scored a high rate of tensile strength in warp direction, tensile strength in weft direction, elongation in warp direction and abrasion resistance, On other hand, the satin 4 weave structure has recorded a high value in tear strength in weft direction and elongation in weft direction.

In this study, the morphological and mechanical performances of hybrid green organic and inorganic filler composites were investigated. Various hybrid reinforcements using natural waste fillers including lemon leaves and eggshells were utilized for the study. The tensile strength, tensile modulus, elongation to break, flexural strength, and flexural modulus were investigated for the composites with polypropylene matrix. The results revealed that eggshells composites had the best values for both tensile and flexural tests while lemon leaves composites had the lowest values. However, the hybrid filler (lemon leaves-eggshells) had intermediate values. The poor properties of lemon leaves were attributed to the agglomeration and weak bonding presented by the morphological analysis of the hybrid composites.

The development of new materials or the improvement of their mechanical properties is a constant challenge in science. Numerous researchers have increasingly concentrated efforts to obtain new and more environmentally friendly materials using natural fibers, which, to be used in engineering applications, usually have to undergo thermochemical treatments. This work aims to evaluate and compare the effects of two low-cost and low-impact thermochemical treatments on Luffa cylindrica (LC) fibers to verify why different mechanical strengths are reached when applying these variations in the production of compressed earth blocks. Samples of LC fibers in three conditions were studied, LC fibers without treatment or natural LC fibers (LN), fibers treated with boiled water (LW) and fibers treated with sodium hydroxide (LS). Samples were analyzed by SEM/EDS to verify surface changes and chemical composition. The lignin, hemicellulose, amorphous and crystalline cellulose structures were determined by FTIR. XRD technique was used to determine the amorphous and crystalline phases, as well as the crystallinity index and the crystallite size. Both treatments decreased the crystallinity index, but the sodium hydroxide treatment has given a crystallinity higher than that of the water treatment. However, the water treatment cannot be ignored. Perhaps more convenient results can be achieved by varying the water treatment time.

Functional materials, in the combination of lignocelluloses, known as natural fibers, with oxide materials, can result in cultivating functional properties such as flexibility, relativity good electrical conduction, good electrical charge storage capacity, and tunable electric permittivity. This study presents the morphological, dielectric, and impedance properties of lignocellulose–lead oxide (LC/PbO2) composite sheets electrodeposited with silver metallic nanoparticles for various time spans. The uncoated samples show a rather simple behavior where the impedance data fit well to the two-system model with different relaxation times. On the other side, the impedance spectra of the electrodeposited sample have varying features, which mainly depend upon the deposition thickness of the Ag particles. The common feature is the drift of conductive species, as seen from the straight-line behavior in the Nyquist plots, which were fitted using a Warburg element in the equivalent circuit model.

Natural life is a phenomenon that exists in the creation of human beings and is focused on fulfilling the purpose of meeting basic needs. In the context of clothing and textiles, people obtained fibers from plants and animal hides and used them to cover their bodies due to the need for protection from cold weather conditions and other environmental factors. With the development of technology and the diversification of materials over time, new techniques have been discovered and fibers have been turned into textile surfaces. These textile surfaces are used with their own natural colors as well as being colored with the help of different natural and artificial dyes. Many colors in different structures and tones can be obtained from natural dye sources such as flowers, leaves, plants, soil and rocks. Within the scope of this study, dyestuffs were obtained from different natural sources and natural fibers were colored with these dyes. Colored fibers were used in different forms and shapes. Within the scope of this study, the importance of marine life and the effects of sea and water pollution on the environment and living life were emphasized. The fiber art work called “Beyond Water” was revealed. The work has been applied on the canvas, and the design process and applied steps have been conveyed., Doğal yaşam, insanoğlunun yaradılışında var olan ve temel ihtiyaçları karşılamak amacını yerine getirmeye odaklı bir olgudur. Giyim ve tekstil bağlamında, insanlar, soğuk hava koşullarından ve diğer çevresel etkenlerden korunma ihtiyacı nedeniyle bitkilerden ve hayvan postlarından lifler elde ederek, vücutlarını örtmek amacıyla kullanmışlardır. Zaman içerisinde teknolojinin gelişmesi ve malzemelerin çeşitlenmesi ile yeni teknikler keşfedilerek lifler tekstil yüzeyleri haline getirilmiştir. Bu tekstil yüzeyleri, kendi doğal renkleri ile kullanıldığı gibi farklı doğal ve yapay boyalar yardımı ile renklendirilerek kullanılmış ve kullanılmaktadır. Çiçek, yaprak, bitki, toprak ve kaya gibi doğal boya kaynaklarından farklı yapıda ve tonlarda pek çok renk elde edilebilmektedir. Bu çalışma kapsamında farklı doğal kaynaklardan boyarmadde elde edilmiş ve yine doğal lifler bu boyalarla renklendirilmiştir. Renklendirilmesi yapılan lifler farklı form ve biçimlerde kullanılmıştır. Bu çalışma kapsamında deniz yaşamının önemi, deniz ve su kirliliğinin çevreye ve canlı yaşamına etkilerine dikkat çekilmiştir. “Suyun Ötesinde” adı verilen lif sanatı çalışması ortaya çıkarılmıştır. Çalışma tuval üzerine uygulanmış olup, tasarım süreci ve uygulanan adımlar aktarılmıştır.

This study aims to present various forms of cellulose, whose shape depends on the source of origin, and to demonstrate the differences in the influence on the properties of materials produced with its participation. For this purpose, composites with various plant additives have been designed and obtained. Some of them have undergone chemical and pyrolytic modifications. The results of the mechanical, physicochemical and microscopic tests showed differences in cellulose structure, even in the case of very similar sources, and its diversified influence on the characteristics of the obtained materials. The research shows the effect of the use of natural additives and their modified versions on the mechanical properties of the composite based on epoxy resin. It turns out that cellulose modifiers are not only fillers that reduce the price of the final product but can also increase some mechanical properties, e.g., compressive strength, which is an additional advantage and a reason for wider use. The potential of natural resources is not yet fully understood. Relatively recently, people have started to be interested in cellulose on a nanometric scale, as it turns out that it can exist in several different forms with interesting properties.

Sve veća zabrinutost o iscrpljivanju resursa, kao i pojava sve većeg zagađenja usmjerila je mnoge znanstvenike i istraživače u posljednjih nekoliko godina na proizvodnju biokompozita. Sve veća komercijalna dostupnost polilaktidna (PLA) kao i njegova dobra svojstva, uključujući biorazgradljivost učinila su ga jednim od obećavajućih materijala. PLA biokompoziti koji sadrže anorganska punila ili ojačavala na osnovi prirodnih vlakana zauzimaju veliku pozornost zbog svoje biokompatibilnosti. Neke od prednosti korištenja prirodnih vlakana u biokompozitima su niska cijena, specifična svojstva i neabrazivna prerada. Zamjena određenog postotka biopolimera s vlaknima smanjuje cijenu materijala, a takvi bi materijali bili i potpuno biorazgradljivi. Shodno tome, istraživači su ispitivali učinkovitost PLA kompozita ojačanog prirodnim vlaknima kao alternativnog materijala za zamjenu neobnovljivih materijala na bazi nafte. The growing concern about the depletion of resources, as well as the appearance of increasing pollution, has directed many scientists and researchers in the last few years to the production of biocomposites. The increasing commercial availability of polylactide (PLA) as well as its good properties, including biodegradability, have made it one of the most promising materials. PLA biocomposites containing inorganic fillers or reinforcements based on natural fibers are attracting a lot of attention due to their biocompatibility. Some of the advantages of using natural fibers in biocomposites are low price, specific properties, and non-abrasive processing. Replacing a certain percentage of biopolymers with fibers reduces the cost of the material, and such materials would also be completely biodegradable. Accordingly, researchers investigated the effectiveness of natural fiber reinforced PLA composites as an alternative material to replace petroleum-based non-renewable materials.

Jute fibers have been studied for their numerous properties and, recently, much attention has been paid to the possibility of using them as reinforcing materialin cement based matrices for structural engineering applications. In the context ofstructural reinforcement methods, the use of composite materials reinforced withsynthetic fibers is now quite common, due to their light weight, versatility and adaptability. However, in recent years, the scientific community has been interested on the use of natural composite materials, with the goal of finding innovativesolutions with renewable, recyclable, sustainable and biodegradable products for the construction industry. This research investigates the use of jute fibers to assesstheir suitability as reinforcing materials in cementitious composites for historic/existing masonry structures retrofitting. As a matter of fact, these applications have to consider the possible low durability of jute, like all other cellulose-based fibers, especially into alkaline environments. This work reports the ongoing experimental investigation to set the mechanical performance of jute fibers. The experimentalprogram considers jute yarns in their natural condition and evaluates how the alkaline matrices would affect the fiber mechanical properties. The paper summa rizes the first results obtained from durability tests on jute yarns as a first step towards the assessment of the long-term performance of Natural Fiber ReinforcedCementitious Composites

In the present paper, the performance recovery under conditions of discontinuous exposure to a marine environment of a natural fiber-reinforced composite (NFRC) reinforced by flax fibers was assessed. In particular, this laminate was initially exposed to salt-fog for 15 and 30 days, and then stored in a controlled air condition for up to 21 days. The flax fiber-reinforced composite showed coupled reversible and irreversible aging phenomena during the wet stage, as well as evidencing a significant mechanical recovery during the dry stage. Unlike the stiffness, the laminate showed a noticeable recovery of its flexural strength. This behavior affected the composite material toughness. A simplified approach was applied to define a topological map of the material toughness at varying drying times. The results highlight that the composite shows maximum toughness at intermediate drying times thanks to the strength recovery, in addition to its residual plasticity. This approach allows us to better determine that the strength is more closely related to reversible degradation phenomena, whereas the stiffness is mainly correlated to irreversible ones, implying relevant effects on the toughness of the composite exposed to a wet/dry cycle.

International audience; Because of their specific properties, vegetal fibers are increasingly used as sustainable polymer reinforcementsfor eco-composites. Nevertheless, their polar character hinders them from being used more frequently at in-dustrial scale due to their incompatibility with mostly dispersive polymers (the cheapest and most commonones). In this study, direct fluorination treatment was carried out to covalently graft fluorine atom at the outmostsurface of flax fibers. Such a grafting has been proved by FT-IR, 19F NMR and XPS spectroscopies, and thesecharacterizations allowed to understand chemical change due to the treatment. This chemical modificationinduced an augmentation of the dispersive character of flax fibers, by significantly lowering the polar componentof surface energy without significant change of the dispersive component. Young’s modulus was also maintained.Thereby, treated fibers become perfectly compatible with hydrophobic polymer, and an improvement in themechanical performance of the resulting composite is expected according to the literature.

In this study, the morphological, physical, and tensile properties of flax were experimentally investigated at three different scales (single fiber, yarn and unidirectional fabric). The cross-sectional area was determined directly using microscopic image and indirectly via linear density with gravimetric and vibroscopic methods. All specimens were tested in tension until failure. The results showed that measured properties and their variability were scale-dependent. The tensile strength and modulus of elasticity were gradually decreasing with the scale and the variabilities were decreasing when going from fibers to yarns and fabric. This difference in the properties should be considered for any multi-scale analysis of the flax reinforcement. The average failure strains of single fiber, yarn and fabric were 2% (±30%), 1.7% (±12%) and 1.7% (±2.8%), respectively. Due to the consistency of failure strain at different material scales, it can be recommended as design criterion. The results of this study can be used for better design and preparation of plant-based natural fiber reinforced polymer composites.

This article presents a new design framework for the specification and prototyping of geometrically and behaviorally complex materials with graded properties, coined predictive information modeling (PIM). The contribution is the development of new circular design workflows employing machine learning for predicting fabrication files based on performance and design requirements. The aim is linking endogenous capacities as well as exogenous environmental dynamics of graded materials, as an approach to material focused intelligent design systems. Using two experimental case studies, the research demonstrates PIM as an applied design framework for addressing (1) material uncertainty, (2) multi-scale data integration, and (3) cyclical fabrication workflows. Through the analysis of these models, we demonstrate research methods that are validated for design applications, review their implications, and discuss further trajectories.

The innovative sustainable technology based on natural fabric-reinforced cementitious matrix (NFRCM) is analyzed for strengthening masonry. A new frontier for composite materials is proposed as an alternative to well-known traditional technologies used to improve the seismic behavior of buildings, such as the portuguese technique ‘gaiola pombalina’, the Italian ‘baraccata house’ and the turkish ‘himis house’. Preliminary sensitivity analysis is performed on NFRCM and ‘baraccata’ numerical models. Both technologies are numerically compared. From the experimental results of in-plane incremental load test carried out by CNR-Ivalsa a numerical model is calibrated by non-linear pushover analysis to evaluate the behavior of masonry wall strengthened with natural fibers. This paper demonstrates the effectiveness of NFRCM systems for strengthening masonry as: i) a non-invasive solution without significant thickness; ii) a sustainable technology; iii) an intervention involving the whole wall surface avoiding failure local mechanisms.