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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

Nowadays, the search for new materials with a sustainable character to reduce the production of residues is under continuous research. In this sense, fully biodegradable composites based on polyhydroxybutyrate and different pretreated fibres coming from barley straw have been fabricated, and their resistance to environmental controlled conditions have been characterized. The materials were already compounded in a kinetic mixer and injection-moulded as specimens for tensile assay to be aged in a Xenotest chamber so as to simulate environmental conditioning. The samples, after accelerated aging, were characterized thus: mechanical characterization (tensile assay), water uptake (immersion and contact angle), and surface observation (optical and SEM microscopy). The incorporation of the fibres helps the composite to keep its structure for a longer time. On the other hand, the presence of the fibres increases the water uptake capacity to allow water permeation in the composite, which allows final degradation, characterised by a significant drop in properties after one month of exposure to simulated environmental conditions.

In this paper, the one-dimensional tensile behavior of Guadua angustifolia Kunth fibre/polypropylene (PP+GAKS) composites is modeled. The classical model of Kelly–Tyson and its Bowyer–Bader’s solution is not able to reproduce the entire stress–strain curve of the composite. An integral (In-Built) micromechanical model proposed by Isitman and Aykol, initially for synthetic fiber-reinforced composites, was applied to predict micromechanical parameters in short natural fiber composites. The proposed method integrates both the information of the experimental stress-strain curves and the morphology of the fiber bundles within the composite to estimate the interfacial shear strength (IFSS), fiber orientation efficiency factor ηFOD, fiber length efficiency factor ηFLD and critical fiber length lc. It was possible to reproduce the stress-strain curves of the PP+GAKS composite with low residual standard deviation. A methodology was applied using X-ray microtomography and digital image processing techniques for the precise extraction of the micromechanical parameters involved in the model. The results showed good agreement with the experimental data This research was funded by Universidad Politécnica Salesiana within the framework of the research project Resolution: N◦ 009-008-2021-11-11

The performance of henequen fibers and polypropylene composites obtained by injection molding with and without coupling agent was evaluated. Henequen fibers are natural non-wood fibers mainly used in textile sector or in thermosetting matrix composites. In this work, henequen fibers have been used as a possible substitute reinforcement material for sized glass fibers. The surface charge density of the materials used was evaluated, as well as the morphology of the fibers inside the material. A significant reduction in the length of the fibers was observed as a consequence of the processing. The use of a 4% coupling agent based on fiber content was found to be effective in achieving significant improvements in the tensile strength of the composites in the reinforcement range studied. The influence of the aspect ratio on the coupling factor was determined, as well as the evaluation of the interface quality. The results obtained demonstrate the great potential of henequen fibers as reinforcement of composite materials, giving rise to strong interfaces with coupling. Finally, the comparison of henequen fiber composites with sized glass fiber composites showed that it is possible to substitute polypropylene composites with 20 wt.% glass fiber for 50 wt.% henequen fibers.

Projecte sorgit de la preocupació per la preservació del medi ambient i la contribució a reduir les emissions de CO2 produïdes en la fabricació, utilització i posterior reciclat dels materials compostos reforçats amb fibra de vidre. Es decideix plantejar objectivament la vertadera viabilitat de substituir les fibres de vidre per una fibra natural que garanteixi un comportament mecànic similar a l’obtingut utilitzant fibres de vidre com a reforç en materials compostos. Es fabriquen uns compostos només diferenciats pel tipus de reforç i caracteritzats a partir d'assajos de tracció i flexió. Gràcies als resultats dels assajos s'avaluen les diferències entre compostos i es determina el potencial de les fibres naturals. Posteriorment, s'avalua a través de simulacions i anàlisis d'esforços, si és factible aplicar aquests compostos en la fabricació de la cúpula de la moto elèctrica de l'equip de competició UPC Vilanova E3 Team. Per acabar, es detallen totes les consideracions de reciclabilitat i sostenibilitat que objectivament cal tenir en compte en tractar amb aquests materials. Proyecto surgido de la preocupación por la preservación del medio ambiente y la contribución a reducir las emisiones de CO₂ producidas en la fabricación, utilización y posterior reciclado de los materiales compuestos reforzados con fibra de vidrio. En este trabajo se plantea objetivamente la verdadera viabilidad de sustituir las fibras de vidrio por una fibra natural que garantice un comportamiento mecánico similar al obtenido utilizando fibras de vidrio como refuerzo en materiales compuestos. Se fabrican unos compuestos solo diferenciados por el tipo de refuerzo y caracterizados a partir de ensayos de tracción y flexión. A partir de los resultados de los ensayos se evalúan las diferencias entre compuestos y se determina el potencial de las fibras naturales. Posteriormente, se evalúa mediante simulaciones y análisis de esfuerzos si es factible aplicar estos compuestos en la fabricación de la cúpula de la moto eléctrica del equipo de competición UPC Vilanova E3 Team. Para finalizar, se detallan todas las consideraciones de reciclaje y sostenibilidad que objetivamente se deben tener en cuenta al tratar con estos materiales. This project stems from concern for preserving the environment and contributing to reduce carbon emissions produced in the manufacture, use and recycling of fibre-reinforced composite materials. It is decided to objectively establish the proper feasibility of replacing glass fibres with a natural fibre that ensures similar mechanical behaviour to that of glass fibres. The manufacture of composites is differentiated only by the type of reinforcement and is characterised by tensile and flexural testing. The results of the tests allow us to evaluate the differences between compounds and the potential of natural fibres is determined. In addition, simulations and effort analysis were conducted to evaluate whether these compounds were feasible for use in the manufacture of electric motorcycle domes for the UPC Vilanova E3 Team competition team. To conclude, all considerations of recyclability and sustainability that must be objectively taken into account are made.

Silk fibroin (SF) has been successfully used for medical devices due to its biodegradability with non-toxic end products, high tensile strength and mechanical robustness, but also because of its high flexibility potential. Although natural silk fibers have excellent strength and flexibility, regenerated silk materials generally become brittle in the dry state. For this reason, researchers have studied the effects that manufacturing and post-treatment parameters have on their mechanical properties, but they have also studied the impact on other factors such as biodegradability on the environment. This work presents an optimized process for direct ink write a regenerated SF bioink and its possible post-treatments. A simple method to concentrate the aqueous SF has been reported. The technique was then employed to 3D print test specimens for multiple mechanical analysis to characterize the resulting parameters of the processed silk. The effect of post-treating the material with different processes (no-treatment, immersion in ethanol for 24 h, and subsequently immersion in methanol for 30, 60 or 120 min) was explored. The different post-treatments resulted in distinct effects on the silk properties, suggesting that SF molecular structure could be controlled by the post-treatment process. The results showed a transition to phosphate-buffered saline (PBS)-insoluble silk when the silk was treated with alcohols. This resulted in a more brittle material than the untreated group, with a lower strain at break. Nevertheless, the post-treatments enhanced the stability of silk in water, as they reported greater insolubility in PBS than the untreated group. This study characterizes and discusses the mechanical properties of SF processed with a novel additive manufacturing method intended for customization of medical devices The authors gratefully acknowledge the support of the Generalitat de Catalunya through the project (BASE3D 001-P-001646) which is co-financed by the European Union Regional Development Fund under the ERDF Operational Program of Catalonia 2014–2020 with a grant of 50% of the total eligible cost. The authors would also like to thank the Generalitat de Catalunya and the European Union for the predoctoral grant FI AGUR 2021FI_B 00363. Finally, special gratitude to La granja de la seda and AERCEGSA for the supply of high quality silk cocoons.

In this study, Young’s modulus of henequen fibers was estimated through micromechanical modeling of polypropylene (PP)-based composites, and further corroborated through a single filament tensile test after applying a correction method. PP and henequen strands, chopped to 1 mm length, were mixed in the presence of maleic anhydride grafted polypropylene (MAPP). A 4 wt.% of MAPP showed an effective enhancement of the interfacial adhesion. The composites were mold-injected into dog-bone specimens and tensile tested. The Young’s modulus of the composites increased steadily and linearly up to 50 wt.% of fiber content from 1.5 to 6.4 GPa, corresponding to a 327% increase. Certainly, henequen fibers showed a comparable stiffening capacity of PP composites than glass fibers. The intrinsic Young’s modulus of the fibers was predicted through well established models such as Hirsch or Tsai-Pagano, yielding average values of 30.5 and 34.6 GPa, respectively. The single filament test performed to henequen strands resulted in values between 16 and 27 GPa depending on the gauge length, although, after applying a correction method, a Young’s modulus of 33.3 GPa was obtained. Overall, the present work presents the great potential for henequen fibers as PP reinforcement. Moreover, relationships between micromechanics models and filament testing to estimate Young’s modulus of the fibers were explored.

The growing environmental consciousness of society has led to the development of sustainable products. Because of its noticeable tensile properties, polylactic acid (PLA) has been widely studied as a replacement for non-degradable and renewable polymers. However, the PLA by itself has a high rigidity that is increased when fibers are incorporated as reinforcement. In this sense, the present work aims to study the feasibility of obtaining compounds with high properties while maintaining a lower stiffness. For this purpose, a mixed PLA-PTA (thermoplastic starch-based polymer) matrix was chosen. The use of PTA to increase the compostability of the material caused the tensile strength decrease of 37.3%, the Young's modulus reduction of 34.9% and the strain decrease of 12.6% compared to PLA matrix when 30% PTA was added. Therefore, blends were reinforced with bleached kraft hardwood fibers (BKHF) to improve their mechanical performance. In the case of the blend with 20% PTA reinforced with 30% BKHF, 51.32 MPa tensile strength (35.4% of increase), 5.54 GPa Young's modulus (112.3% of increment) and a strain of 4% (23.5% of gain). Thermal, morphological and macro-mechanical properties of blends were investigated. It was found that the tensile properties and the interphase of the two components were fairly good in comparison with the literature. The study has allowed us to conclude through a preliminary LCA that it is possible to obtain materials with the same properties of PP with a 33.6% reduction in the carbon footprint. Thus, BKHF reinforced biocomposites are postulated as a real alternative to replace non-renewable ones This research was funded by the MAT2017-83347-R grant of the Spanish Ministry of Economy and Competitiveness Open Access funding provided thanks to the CRUE-CSIC agreement with Elsevier

The use of natural fibers as reinforcement for polymer-based composites has been attracting the interest of the scientific community for a long time. Despite the maturity of natural fiber-reinforced polymers, such materials continue to arouse the interest of researchers

Biocomposites are composite materials where at least the matrix or the reinforcement phases are obtained from natural and renewable resources. Natural fibers for composite preparation can be obtained from annual plants, wood, recycled products, or agroforestry waste. The present work selected abaca strands, spruce fibers, recycled fibers from old newspaper, and barley fibers as raw materials to produce biocomposites, in combination with a biobased polyethylene. One very important feature in material science and for industrial applications is knowing how a material will deform under load, and this characteristic is represented by Young’s modulus. Therefore, in this work, the stiffness and deformation of the biocomposites were determined and evaluated using macromechanics and micromechanics analyses. Results were compared to those of conventional synthetic composites reinforced with glass fibers. From the micromechanics analysis, the intrinsic Young modulus of the reinforcements was obtained, as well as other micromechanics parameters such as the modulus efficiency and the length and orientation factors. Abaca strands accounted for the highest intrinsic modulus. One interesting outcome was that recycled fibers exhibited similar Young’s moduli to wood fibers. Finally, agroforestry waste demonstrated the lowest stiffening potential. The study explores the opportunity of using different natural fibers when specific properties or applications are desired.

Glass fibre is the most widely used material for reinforcing thermoplastic matrices presently and its use continues to grow. A significant disadvantage of glass fibre, however, is its impact on the environment, in particular, due to the fact that glass fibre-reinforced composite materials are difficult to recycle. Polyamide 6 is an engineering plastic frequently used as a matrix for high-mechanical performance composites. Producing polyamide monomer requires the use of a large amount of energy and can also pose harmful environmental impacts. Consequently, glass fibre-reinforced Polyamide 6 composites cannot be considered environmentally friendly. In this work, we assessed the performance of a road cycling pedal body consisting of a composite of natural Polyamide 11 reinforced with lignocellulosic fibres from stone-ground wood, as an alternative to the conventional glass fibre-reinforced Polyamide 6 composite (the most common material used for recreational purposes). We developed a 3D model of a pedal with a geometry based on a combination of two existing commercial choices and used it to perform three finite-element tests in order to assess its strength under highly demanding static and cyclic conditions. A supplementary life cycle analysis of the pedal was also performed to determine the ecological impact. Based on the results of the simulation tests, the pedal is considered to be mechanically viable and has a significantly lower environmental impact than fully synthetic composites.

The research toward environmentally friendly materials has devoted a great effort on composites based on natural fiber-reinforced biopolymers. These materials have shown noticeable mechanical properties, mainly tensile and flexural strengths, as a consequence of increasingly strong interfaces. Previous studies have shown a good interface between natural fibers and poly (lactic acid) (PLA) when these fibers present a low lignin content in their surface chemical composition (bleached fibers). Nonetheless, one of the main drawbacks of these materials is the hydrophilicity of the reinforcements in front of the mineral ones like glass fiber. Meanwhile, the behavior of such materials under impact is also of importance to evaluate its usefulness. This research evaluates the water uptake behavior and the impact strength of bleached Kraft softwood-reinforced PLA composites that have been reported to show noticeable tensile and flexural properties. The paper explores the differences between these bio-based materials and commodity composites like glass fiber-reinforced polypropylene This research was funded by the MAT2017-83347-R grant of the Spanish Ministry of Economy and Competitiveness

Natural fiber-reinforced thermoplastic composites can be an alternative to mineral fiber-based composites, especially when economic and environment concerns are included under the material selection criteria. In recent years, the literature has shown how lignocellulosic fiber-reinforced composites can be used for a variety of applications. Nonetheless, the impact strength and the water uptake behavior of such materials have been seen as drawbacks. In this work, the impact strength and the water uptake of composites made of polypropylene reinforced with fibers from recycled newspaper have been researched. The results show how the impact strength decreases with the percentage of reinforcement in a similar manner to that of glass fiber-reinforced polypropylene composites as a result of adding a fragile phase to the material. It was found that the water uptake increased with the increasing percentages of lignocellulosic fibers due to the hydrophilic nature of such reinforcements. The diffusion behavior was found to be Fickian. A maleic anhydride was added as a coupling agent in order to increase the strength of the interface between the matrix and the reinforcements. It was found that the presence of such a coupling agent increased the impact strength of the composites and decreased the water uptake. Impact strengths of 21.3 kJ/m3 were obtained for a coupled composite with 30 wt % reinforcement contents, which is a value higher than that obtained for glass fiber-based materials. The obtained composites reinforced with recycled fibers showed competitive impact strength and water uptake behaviors in comparison with materials reinforced with raw lignocellulosic fibers. The article increases the knowledge on newspaper fiber-reinforced polyolefin composite properties, showing the competitiveness of waste-based materials This research was funded by the Chair on Sustainable Industrial Processes of the University of Girona, ref 01/2019

The automotive industry is under a growing volume of regulations regarding environmental impact and component recycling. Nowadays, glass fiber-based composites are commodities in the automotive industry, but show limitations when recycled. Thus, attention is being devoted to alternative reinforcements like natural fibers. Curauá (Curacao, Ananas erectifolius) is reported in the literature as a promising source of natural fiber prone to be used as composite reinforcement. Nonetheless, one important challenge is to obtain properly dispersed materials, especially when the percentages of reinforcements are higher than 30 wt %. In this work, composite materials with curauá fiber contents ranging from 20 wt % to 50 wt % showed a linear positive evolution of its tensile strength and Young’s modulus against reinforcement content. This is an indication of good reinforcement dispersion and of favorable stress transfer at the fiber-matrix interphase. A car door handle was used as a test case to assess the suitability of curauá-based composites to replace glass fiber-reinforced composites. The mechanical analysis and a preliminary lifecycle analysis are performed to prove such ability This research was funded by the Chair on Sustainable Industrial Processes of the University of Girona, ref 01/2019

The present paper investigates the acoustic properties of natural fiber reinforced composites. Fibers from orange tree pruning were obtained and subject to different treatments in order to obtain mechanical, thermomechanical and chemi-thermomechanical pulps. These pulps were used as reinforcement for a polypropylene matrix. The obtained composite materials were submitted to acoustical tests in an impedance tubes device. The transmission losses obtained against the fiber content were obtained and discussed. Latter it was researched the influence of the fiber treatments on the soundproof characteristics. A numerical method was used to preview the acoustic insulation of the materials against the sound frequency. Finally the results were compared with that of the most usual lightweight soundproof solutions. (C) 2014 Elsevier Ltd. All rights reserved.

The strength of the interphase between the reinforcements and the matrix has a major role in the mechanical properties of natural fiber reinforced polyolefin composites. The creation of strong interphases is hindered by the hydrophobic and hydrophilic natures of the matrix and the reinforcements, respectively. Adding coupling agents has been a common strategy to solve this problem. Nonetheless, a correct dosage of such coupling agents is important to, on the one hand guarantee strong interphases and high tensile strengths, and on the other hand ensure a full exploitation of the strengthening capabilities of the reinforcements. The paper proposes using topographic profile techniques to represent the effect of reinforcement and coupling agent contents of the strength of the interphase and the exploitation of the reinforcements. This representation allowed identifying the areas that are more or less sensitive to coupling agent content. The research also helped by finding that an excess of coupling agent had less impact than a lack of this component This research was funded by the Chair on Sustainable Industrial Processes of the University of Girona, ref 01/2019

Hemp core is a lignocellulosic residue in the production chain of hemp strands. Huge amounts of hemp core are gathered annually in Europe (43,000 tons) with no major application end. Such lignocellulosic wastes have potential as filling or reinforcing material to replace synthetic fibers and wood fibers in polymer composites. In this study, hemp core biomass was treated under different NaOH concentrations and then defibrated by means of Sprout Waldron equipment to obtain single fibers. Polypropylene matrix was reinforced up to 50 wt.% and the resulting hemp core fibers and the flexural properties were investigated. The results show that the flexural strength of composites increased with the intensity of NaOH treatment. The effect of NaOH was attributed to the removal of extractives and lignin in the fiber cell wall leading to improved interfacial adhesion characteristics. Besides, a methodology was established for the estimation of the intrinsic flexural strength of hemp core fibers. The intrinsic flexural strength of hemp core fibers was calculated to be 940 MPa for fibers treated at 10 wt.% of NaOH. In addition, a relationship between the lignin content and the intrinsic strength of the fibers was established This research was funded by Spain’s DGICyT, MICINN within the framework of the Projects CTQ2016-78729-R and supported by the Spanish Ministry of Science and Education through the National Program FPU (Grant Number FPU14/02278)

© 2020 by the authors., Nowadays, the interest on nanofibrillated cellulose (CNF) has increased owing to its sustainability and its capacity to improve mechanical and barrier properties of polymeric films. Moreover, this filler shows some drawbacks related with its high capacity to form aggregates, hindering its dispersion in the matrix. In this work, an improved procedure to optimize the dispersability of CNF in a thermoplastic starch was put forward. On the one hand, CNF needs a hydrophilic dispersant to be included in the matrix, and on the other, starch needs a hydrophilic plasticizer to obtain a thermoformable material. Glycerol was used to fulfil both targets at once. CNF was predispersed in the plasticizer before nanofibrillation and later on was included into starch, obtaining thin films. The tensile strength of these CNF–starch composite films was 60% higher than the plain thermoplastic starch at a very low 0.36% w/w percentage of CNF. The films showed a noticeable correlation between water uptake, and temperature and humidity. Regarding permeability, a ca. 55% oxygen and water vapor permeability drop was found by nanofiller loading. The hydrolytic susceptibility of the composite was confirmed, being similar to that of the thermoplastic starch., This research was funded by University of Girona through the Program of the Improvement of the Scientific Production and the MINECO project AGL2015-63855-C2-1-R.

In this article, with the aim of promoting sustainability, contributing to the circular economy and the fight against climate change, the production of composite materials from Bio-polyethylene reinforced with corn stover fibers has been studied. The behavior of the materials obtained has been studied experimentally and by mathematical models of micromechanics. The composite materials were produced by extrusion and then injection with from 10 to 50 wt.% of fibers. The creation of a good fiber-matrix interface was studied by the incorporation of coupling agent between (0&ndash, 8 wt.%). Increase of 131.2% on tensile strength for 40wt.% reinforcement was achieved by adding 6 wt.% of coupling agent. The correct interface was demonstrated by a correlation of 0.99 between the experimental results and the results of the mathematical models used.

[CA] El present projecte té com a objecte dissenyar i desenvolupar un llit per a gats realitzat amb materials duradors, de fàcil manufactura i amb un reduït impacte ambiental. Comprèn l'estudi del mercat actual i les necessitats i factors que afecten a aquesta tipologia de producte, per tal de desenvolupar un disseny conceptual, estudiar la fabricació d’aquest i realitzar el seu prototip. A més, es desenvolupen els aspectes genèrics de comunicació de marca. L'element més representatiu està realitzat amb fibres vegetals d'espart, treballat per un artesà de la Comunitat Valenciana, posant en valor l'ofici, revitalitzant-lo i afavorint el comerç local i de quilòmetre zero., [ES] El presente proyecto tiene como objeto diseñar y desarrollar una cama para gatos realizada con materiales duraderos, de fácil manufactura y con un reducido impacto ambiental. Comprende el estudio del mercado actual y las necesidades y factores que afectan a esta tipología de producto, para desarrollar un diseño conceptual, estudiar la fabricación de este y realizar su prototipo. Además, se desarrollan los aspectos genéricos de comunicación de marca. El elemento más representativo está realizado con fibras vegetales de esparto, trabajado por un artesano de la Comunidad Valenciana, poniendo en valor el oficio, revitalizándolo y favoreciendo el comercio local y de kilómetro cero., [EN] This project aims to design and develop a bed for cats made of durable materials, easy to manufacture and with a reduced environmental impact. It includes the study of the current market and the needs and factors that affect this type of product to develop a conceptual design, study the manufacturing of the product, and make its prototype. In addition, the generic aspects of brand communication are developed. The most representative element is made with esparto grass fibres, carried out by a craftsman from the Valencian Community, enhancing its value, revitalising it and favouring the local and kilometre zero trade.

En els últims anys un percentatge elevat de fibres d’origen natural han estat substituïdes per fibres d’origen artificial. La utilització creixent d’aquestes fibres té unes conseqüències fatídiques pel planeta ja que aquestes fibres no són biodegradables i es presenten com una amenaça pels ecosistemes. És pot distingir d’entre més de 15 fibres naturals d’origen vegetal arreu del món. Moltes d’aquestes fibres representen un subproducte de la planta de la qual s’extreu. El fet d’utilitzar aquestes fibres representa un major grau d’aprofitament del cultiu i per tant, un benefici econòmic sense incrementar la producció de matèria prima. En aquest projecte s’estudiarà el procés d’extració de la fibra de la pellofa de blat de moro ja que representa un subproducte de la producció del blat de moro. S’analitzaran també les diferents propietats morfològiques i mecàniques i les possibles aplicacions al món de la indústria tèxtil

Newspapers have a limited lifespan, and therefore represent a focus of used and disposed paper. While these refuses have a considerable value and can be easily recycled, a considerable fraction ends in landfill. The authors show the possibility of adding value to used newspaper and enlarge its value chain. Old newspaper incorporates a high amount of wood fibers able to be used as reinforcement. On the other hand, this material also incorporates inks and other components inherent to newspaper production. In this work, the authors disintegrate old newspaper to recover and individualize wood fibers. A morphological analysis showed that the recovered fibers had aspect ratios higher than 10, revealing, a priori, their strengthening capabilities. Thereupon, these fibers were compounded with polypropylene at different contents, ranging from 20% to 50% w/w. It is well known that wood fibers are hydrophilic, while polyolefin are hydrophobic. This is a drawback to obtaining strong interfaces. Thus, two sets of composites were produced, with and without a coupling agent. The results showed that uncoupled composites increased the flexural strength of the matrix but reached an equilibrium point from which adding more reinforcement did not changer the flexural strength. On the other hand, the coupled composites showed a linear increase of the flexural strength against the reinforcement content. The flexural moduli of the coupled and uncoupled composites were very similar and evolved linearly with the reinforcement content.

This study examines the use of alkenyl succinic anhydride (ASA)-surface treated calcium carbonate as a functional mineral additive for application in wood fiber (WF)-reinforced PLA composites. The influence of addition quantity on the material properties of PLA composites with 40 wt% fiber reinforcement was examined at mineral addition levels of 10 wt%, 20 wt% and 30 wt%, respectively. The benefits of ASA surface-treated calcium carbonate over untreated mineral were exemplified by comparing the thermomechanical properties of PLA composites at an addition level of 10 wt%. The results demonstrate that the addition of ASA-treated calcium carbonate has distinctive advantages over untreated mineral, in terms of both processability and material properties. First, it enables better control of the process by reducing the flowability of the PLA matrix. Furthermore, it improves the fiber adhesion with the PLA, allowing for a substantial reduction of PLA content in the composite formulation while maintaining material properties.

Poly(lactic acid) (PLA) is one of the most well-known biopolymers. PLA is bio-based, biocompatible, biodegradable, and easy to produce. This polymer has been used to create natural fiber reinforced composites. However, to produce high-performance and presumably biodegradable composites, the interphase between PLA and natural fibers still requires further study. As such, we aimed to produce PLA-based composites reinforced with a commercial bleached kraft eucalyptus pulp. To become a real alternative, fully biodegradable composites must have similar properties to commercial materials. The results found in this research support the competence of wood fiber reinforced PLA composites to replace other glass fiber reinforced polypropylene composites from a tensile property point of view. Furthermore, the micromechanics analysis showed that obtaining strong interphases between the PLA and the reinforcement is possible without using any coupling agent. This work shows the ability of totally bio-based composites that fulfill the principles of green chemistry to replace composites based on polyolefin and high contents of glass fiber. To the best knowledge of the authors, previous studies obtaining such properties or lower ones involved the use of reagents or the modification of the fiber surfaces&rsquo

The main goal of this thesis is the production and characterization of composites materials from a bio-based polyamide and natural fibres which could be more sustainable alternative to glass fibre reinforced polypropylene. The produced composites materials were mechanically characterized and their properties modelled. The thermal,thermomechanical properties and the structure of the composites were analyzed due to the low degradation temperature of the natural fibres similar to the processing temperatures of the composites materials. Moreover, the fibres could have an influence on the structure and the main temperatures of the polymer matrix. Additionally, water uptake test were performwed for all the produced materials. Finally, a piece/product was modelled in order to analyze the technical viability and the sustainability of the produced composite materials L’objectiu principal d’aquesta tesi és l’obtenció i caracterització de materials compostos d’una poliamida d’origen renovable i fibres naturals que puguin ser una alternativa molt més sostenible al polipropilè amb fibra de vidre. Els materials compostos produïts es van caracteritzar mecànicament i les propietats obtingudes van ser modelades. També es van estudiar les propietats tèrmiques, termomecàniques i estructurals dels compostos produïts ja que la temperatura de degradació de les fibres naturals és similar a la temperatura de processat dels materials compostos i la presencia de les fibres podien produir un efecte sobre l'estructura i temperatures caracaterístiques de la matriu. A més a més, es va analitzar el comportament d’absorció d’aigua per part dels materials compostos. Finalment, es va modelitzar una peça/producte per tal d'analitzar la viabilitat técnica i la sostenibilitat dels materials compostos obtinguts

The formulation of greener composite materials by substituting glass fibers with natural fibers is a current field of research. If such natural fiber reinforcements come from industrial side streams, as hemp core fibers (HCFs) come from the extraction of hemp strands for the textile industry, an additional advantage can be identified. Nonetheless, such by-product fibers show some drawbacks, such as high lignin contents, which can make it difficult to obtain a good interphase between the fibers and the matrix and to obtain a good fiber individualization. A digestion treatment at different NaOH contents is proposed to eliminate soluble lignin and extractives from the surface of the fibers. At the same time, the use of a coupling agent solves incompatibilities between the fibers and the matrix. The composites were tensile tested and the impact of the proposed treatments is evaluated and discussed. Later, the Kelly-Tyson modified equation and a modified rule of mixtures—the micro-mechanic models—is used to study the impact of such treatments on the quality of the interphase between the polymer and the reinforcement. Both treatments showed a high impact on the tensile strength and the quality of the interphase, obtaining competitive composite materials reinforced with HCFs derived from a by-product

O crescente consumo de materiais poliméricos originários de fontes não renováveis (base petroquímica), apresentam baixo potencial de biodegradabilidade, e podem demorar desde décadas, até séculos, para se decompor por meio de processos naturais, promovem impactos socioambientais negativos no ambiente. Ao basear-se na percepção de que os recursos naturais não renováveis tendem a escassez, surge a necessidade de buscar recursos de fontes renováveis, como é o caso das fibras vegetais, que são extraídas de plantas renováveis e sustentáveis, e podem ser obtidas de diversas fontes, devido a sua composição química, constituem-se principalmente de celulose e lignina. Diante do desafio de aumentar o campo de aplicação das fibras naturais e dos polímeros biodegradáveis, em uma primeira etapa, foram analisadas as características térmicas de duas fibras naturais existentes oriundas de plantas/árvores/frutos nativos (casca do coco de Babaçu, casca da castanha de Barú) in natura e após o processo de mercerização e branqueamento. Como resultados verificou-se que as fibras naturais empregadas sofrem alterações químicas e estruturais como a remoção dos constituintes amorfos da estrutura: a lignina, hemicelulose, ceras e compostos álcali-solúveis, em virtude do processo de mercerização/branqueamento aplicado. Essas alterações influenciam na estabilidade térmica, que melhoraram nas amostras branqueadas, cerca de 4% para a fibra de babaçu, e 11,71% para a fibra de barú, quando comparadas as fibras in natura

Through this project has been studied the optimal method of extraction of the fiber present in the banana leaves for its possible union to other materials such as cement for the formation of a compound intended to the construction sector. The mechanical properties of the fiber have been varied by a treatment with sodium hydroxide at the optimum concentration. These properties have been analyzed by different fiber characterization tests: optical microscopy and SEM, tensile tests, FTIR spectroscopy and ash content. The values obtained in these tests with banana fibers have been compared with those obtained in flax and hemp fibers, in order to evaluate their properties with regard to two very well-known natural fibers

The aim of this study is to develop a process to produce high-performance cement-based composites reinforced with flax nonwoven fabrics, analyzing the influence of the fabric structure—thickness and entanglement—on mechanical behavior under flexural and tensile loadings. For this purpose, composite with flax nonwoven fabrics with different thicknesses were first prepared and their cement infiltration was evaluated with backscattered electron (BSE) images. The nonwoven fabrics with the optimized thickness were then subjected to a water treatment to improve their stability to humid environments and the fiber-matrix adhesion. For a fixed thickness, the effect of the nonwoven entanglement on the mechanical behavior was evaluated under flexural and direct tension tests. The obtained results indicate that the flax nonwoven fabric reinforcement leads to cement composites with substantial enhancement of ductility.

Greener composites, as alternatives to more common materials, should also achieve technical and economic feasibility to be commercially competitive. This study presents the results obtained from using a biodegradable starch-based matrix, and a natural fiber reinforcement coming from sugarcane bagasse, currently an agro-waste. The sugarcane bagasse biomass was treated to obtain four kinds of fibers with different morphological and chemical properties. The fibers were used to obtain composite materials, which were then tested for tensile properties. The results showed that some of the composites were suitable to replace high density polyethylene, from a technical and environmental point of view. The comparatively higher cost of the biobased matrices hinders the substitution, but the higher the fiber content, the lower the economic disadvantage. A micromechanical test and a sensitivity analysis showed that the fiber orientation had the highest impact on the tensile strength, followed by the fibers mean length and the quality of the interphase between the fibers and the matrix.

Noise, caused by the society and technical progress, is nowadays considered a pollutant. Noise pollution affects or could affect a great number of people. One the most concerned fields, in part by a growing law framework and by the quality expectations of the clients, is architecture. The solution to sound pollution involves eliminating it or reducing it to acceptable levels. Nowadays, one of the most recurred solutions is the use of lightweight materials such as gypsum boards, to create acoustic insulation elements. On the other hand, the environmental awareness has increased the attention towards recycled materials. In the case of composite materials, major attention has been devoted to the substitution of mineral reinforcements, such as glass fibers, by more sustainable reinforcements, as wood fibers or agroforestry wastes. In this sense, olive stones, which are a byproduct of olive oil extraction, could be used. In the present work, olive stone filled polypropylene composites were prepared. Different percentages of filler were used. The soundproofing properties of the composites were tested by means of an impedance tube. Then, the results were compared with those for gypsum boards, wood veneer and wood fiber reinforced polypropylene

[EN] Within this dissertation high performance fiber reinforced cement based composites (HPFRCCs) with natural fibers have been analyzed. The natural fibers come from Brazil, through the international research project EnCoRe ¿ ENvironmentally-friendly solution for COncrete with REcycled and natural components. The autogenous and drying shrinkage of composites with different types of fibres have been studied and compared with the reference mixture without fiber, in order to support the assumption that natural fibers can create a porous network and a preferred way to connect the internal matrix and the environment., [CA] "Dins d' aquest treball sobre els formigons fibroreforzados d'alta resistència, ha sigut analitzat l'efecte que produïxen les fibres d'acer i/o naturals en la retracció d'aquest tipus de formigó. Les fibres naturals provenen de Brasil, a través del projecte d'investigació internacional Encore - solució respectuosa del medi ambient per al formigó amb components naturals ireciclats. La retracció del formigó ha sigut avaluada per a materials compostos amb una fracció de volum de fibra de 1,28%, Ha sigut estudiada la retracció autògena i assecat dels materials compostos amb diferents tipus de fibres comparant amb la mostra de referència que no conté cap fibra a fi de recolzar la hipòtesi que les fibres naturals poden crear una xarxa porosa de manera que connecten la matriu interna i el medi ambient., [ES] Dentro de este trabajo sobre los hormigones fibroreforzados de alta resistencia, ha sido analizado el efecto que producen las fibras de acero y/o naturales en la sobre la retracción sobre este tipo de hormigón. Las fibras naturales provienen de Brasil, a través del proyecto de investigación internacional Encore - solución respetuosa del medio ambiente para el hormigón con compoentes naturales y reciclados. La retracción del hormigón ha sido evaluada para materiales compuestos con una fracción de volumen de fibra de 1,28%, Ha sido estudiada la retracción autógena y secado de los materiales compuestos con diferentes tipos de fibras comparado con la muestra de referencia que no contiene ninguna fibra con el fin de apoyar la hipótesis de que las fibras naturales pueden crear una red porosa de forma que conectan la matriz interna y el medio ambiente.

The present PhD work has been done within the research topics of the Laboratory of Paper Engineering and Polymer Materials (LEPAMAP) at the University of Girona. Composite materials from high yield corn biomass fibers reinforced polypropylene homopolymer matrix had been prepared. The composites were formulated with up to 50wt% fiber contents. The main interest was to determine the mechanical properties of composite materials, micromechanics of the fibers and the composites and the application of the materials on the industrial design of products., Aquest treball ha estat realitzat dintre el marc i les línies de treball del Laboratori d’Enginyeria Paperera i Materials Polímers (LEPAMAP) de la Universitat de Girona. Partint de fibres de biomassa de blat de moro s’han formulat materials compostos amb fins a un 50% en pes, amb i sense agents d’acoblament, i un polipropilè homopolímer com a matriu polimèrica. El principal interès ha estat conèixer les propietats mecàniques dels materials compostos, la micromecànica de les fibres i dels compostos y la aplicació dels materials al disseny industrial de nous productes.

The cellular structure and mechanical properties in compression of starch-based foams filled with natural reinforcements, such as grape wastes, cardoon wastes and barley straw fibers, have been studied in this work. The foams were produced by a microwave foaming process in which water is the plasticizer and at the same time the blowing agent. The use of thermoformed sheets as solid precursors for foaming allowed the production of foamed blocks with cells elongated in the expansion direction and with better properties in terms of rigidity and strength than foams produced in previous works by microwave heating of pellets. Moreover, the natural reinforcements increased not only the rigidity and strength, but also the toughness of these foams. Finally, the modeling of the compressive modulus using scaling laws shows how the stabilization of the cellular structure by the drying of the polymer matrix increases the rigidity of the solid cell walls. The flexible solid thermoplastic starch based precursor turns while foaming into a rigid starch-based foam, which could be suitable either for structural applications, due to its high stiffness and strength, or for packaging due to its complete biodegradability under controlled conditions.