Letteratura scientifica selezionata sul tema "Vegetal-Composite"

Composites of different composition and structure have been obtained on the basis of crushed porous stems of Sosnovsky's hogweed modified with borazote for biostability with the use of organopolymer binders. The particle size of the plant material varied from 1 to 10 mm. Polyvinyl acetate, polyurethane, and casein were used as binders. The ratio of the components (vegetable raw material: polymer) in the composites was 3:1 by mass. Biostability and thermophysical properties of the composites obtained were investigated by applying appropriate GOST methods. It was established that the preliminary modification of vegetable raw material particles with monoethanolamine (NB)-trihydroxyborate provides 100% biostability of composite materials based on used raw materials and organopolymer binders. The use of the above modifier is equally effective for all composites obtained using different types of binders: polyurethane, polyvinyl acetate, and casein. The composites obtained on the basis of modified plant raw materials and organopolymer binders are heat-insulating materials characterized by appropriate coefficients of thermal conductivity and density. Composites based on polyurethane binders have lower thermal conductivity compared to composites based on polyvinyl acetate and casein binders and belong to class A. The polyurethane binder provides the resulting composites with a particle size of 5 mm with an increased compressive strength as compared to the composites based on polyvinyl acetate and casein binders. Thus, the optimal composition of biostable heat insulating material is the composition based on modified plant raw materials with a particle size of 5 mm and polyurethane binder.

We have shown in defect experiments that an 8-cell embryo of Xenopus laevis consists of three kinds of cells, that is, animal, vegetal dorsal and vegetal ventral cells, and that cells of different kinds are distinctly different in their developmental capacity. Complete pattern formation occurs in any defect embryo which contains at least two animal, one vegetal dorsal and one vegetal ventral cell. In the present transplantation experiments, we replaced one or two cells of one 8-cell embryo by those of another to obtain 29 series of composite embryos, in which the cell composition of an embryo and/or the dorsoventral orientation of individual cells differed from those of a normal 8-cell embryo. The resulting embryos were examined macroscopically when controls reached stage 26 (tailbud stage) and later. The results showed that both the two animal dorsal cells or one vegetal dorsal cell could be replaced by animal ventral cells or a vegetal ventral cell, respectively, without any detectable effect on pattern formation, irrespective of the ventrodorsal direction of the ventral cells. On the other hand, replacement of an animal ventral or a vegetal ventral cell by an animal dorsal or a vegetal dorsal cell, respectively, made most composite embryos twins. Twins were also formed when a left-handed vegetal dorsal cell was replaced by a right-handed counterpart and vice versa. In these composite embryos, the dorsoventral orientation of the transplanted cell was different from that of a resident dorsal cell or cells of a recipient, and several lines of evidence show that the dorsal cell transplanted in an off-axis orientation is responsible for twin formation. Thus, dorsal cells have the capacity to form dorsal axial structures at later stages and this capacity is localized on the dorsal side, and endows the cells with polarity. On the other hand, ventral cells did not have this capacity or polarity, judging from the fact that their orientation had no effect on pattern formation. One vegetal dorsal or ventral cell could be replaced by an animal dorsal or ventral cell, respectively, without any marked effect. However, replacement of two vegetal cells by animal ones and of one or two animal cells by vegetal ones resulted in deficiency of vegetal cells and oedema and in deficiency of animal cells and incomplete invagination, respectively. Twin formation in composite embryos with animal dorsal cells in place of animal ventral ones is discussed in consideration of findings in recombination experiments by Nieuwkoop.

The utilization of the vegetal fabric-reinforced cementitious matrix (FRCM) represents an innovative approach to composite materials, offering distinct sustainable advantages when compared to traditional steel-reinforced concrete and conventional FRCM composites employing synthetic fibers. This article introduces a design for sandwich solutions based on a core of extruded polystyrene and composite skins combining mortar as a matrix and diverse vegetal fabrics as fabrics such as hemp and sisal. The structural behavior of the resulting sandwich panel is predominantly driven by the interaction between materials (mortar and polyurethane) and the influence of shear connectors penetrating the insulation layer. This study encompasses an experimental campaign involving double-shear tests, accompanied by heuristic bond-slip models for the potential design of sandwich solutions. The analysis extends to the examination of various connector types, including hemp, sisal, and steel, and their impact on the shear performance of the sandwich specimens. The results obtained emphasize the competitiveness of vegetal fabrics in achieving an effective composite strength comparable to other synthetic fabrics like glass fiber. Nevertheless, this study reveals that the stiffness of steel connectors outperforms vegetal connectors, contributing to an enhanced improvement in both stiffness and shear strength of the sandwich solutions.

The effects of the fly ash and of the sunflower stalks and corn cobs within a cement-matrix composite were studied under the aspects of density, compressive strength, splitting tensile strength, elasticity modulus, and resistance to repeated freeze-thaw cycles. In the research were developed 20 recipes of cement-based composite, including the reference composite. Fly ash was used as partial cement replacement (10, 20 and 30% by volume), and the vegetal aggregates made by corn cobs and sunflower stalks as partial replacement of the mineral aggregates (25 and 50% by volume). The study results revealed that a lightweight composite can be obtained with 50% of vegetal aggregates, and the fly ash, no matter its percentage, enhanced the compressive strength and splitting tensile strength of the compositions with 50% of sunflower aggregates and the freeze-thaw resistance of all compositions with sunflower stalks.

O presente estudo tem como objetivo principal desenvolver um compósito cimentício reforçado com fibras de arumã. O intuito é agregar valor a uma planta típica da região Amazônica, denominada arumã, pertencente à espécie do gênero Ischnosiphon arouma (aubl) Korn e originária da família Maranthaceae, de tal modo que possa ser obtido um Novo Material. Na primeira etapa do estudo foi realizada a caracterização da fibra vegetal de arumã e de todos os componentes da matriz cimentícia, a qual compreendeu ensaios químicos, físicos e mecânicos para a investigação e avaliação de suas propriedades. Na etapa seguinte, adotou-se o procedimento de trabalhar as características físicas e mecânicas das fibras junto à matriz cimentícia, compreendendo um estudo da modificação superficial da fibra por meio de tratamentos químicos à base de soluções de hidróxido de sódio ou utilizando processos com água quente e hornificação. Na terceira etapa, foram produzidas placas reforçadas com fibras sem e com tratamento, as quais, parte delas foram submetidas à cura por 28 dias e as restantes ao ensaio de envelhecimento acelerado. Os resultados obtidos na caracterização das fibras de arumã indicam o seu potencial uso como elemento de reforço para compósitos cimentícios. Por outro lado, os compósitos produzidos com telas de fibra de arumã sem e com tratamento (hornificação e alcalino), apresentaram comportamento pouco dúctil e com baixa resistência, como consequência da degradação das fibras na matriz cimentícia. Isso foi confirmado por meio de ensaios de envelhecimento acelerado com ciclos de molhagem e secagem.
This present study aims to develop a cementation composite reinforced with arumã fiber. The aim is to aggregate value to a typical plant of the Amazon region, called arumã, belonging to species of the genus Ischnosiphon arouma (Aubl) Korn and originally from Maranthaceae family, so that, it can be obtained a New Material. In the first stage of the study was performed the characterization the vegetable fiber arumã and all components of the cementicious matrix, which comprised chemical, physical and mechanical tests for research and evaluation of their properties. In the next stage, it was adopted the procedure of working the physical and mechanical characteristics of the fibers with the cementitious matrix comprising a study of the surface of the fiber modification by chemical treatments using sodium hydroxide solution or employing procedures with hot water and hornification. In the third step, the reinforced plates were produced without and with treatment, which, part of were subjected to cure for 28 days and the remaining subjected to the accelerated aging test. The results obtained in the characterization of arumã fibers indicate its potential use as a reinforcement element for cementicious composites. On the other hand, the composites produced with arumã fiber fabrics without and with a treatment (hornification and alkaline) showed slightly ductile behavior and low strength as a result of degradation of fibers in the cementitious matrix. This was confirmed through accelerated aging tests with wetting and drying cycles.

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The cowpea is a main source of vegetable protein for the people of lower purchasing power of Asia, Africa, Europe and North America, Central and South. In the North and Northeast of Brazil, represent one the most important leguminous food of the diet. Most of the genotypes grown in the world have simple inflorescence. However, cultivars with composite inflorescence were find in cowpea. The aim this work was to study the inherintance of the characters related to production and to inflorescence in crosses between genotypes with simple inflorescence and composite inflorescence. The work was realized at Embrapa Meio-Norte, in Teresina, PI, in the years from 2006 to 2007. It was been made crosses between TVx 5058-09C (P2) x Cacheadoroxo (P1) and Cacheado-roxo (P1) x AU94-MOB-816 (P3). The genitor Cacheadoroxo with composite inflorescence and the other two genitors presenting simple inflorescence. The parents, the generations F1's, F2's and the backcrosses were evaluated in complete randomized blocks design with six repetitions. The parents and F1's consisted of a plot per block, the F2 generations and the backcrosses consisted of five and two rows per block, respectively. The plots were represented per one row with 7,0 m of length, the spacing between rows was 1,0 m and between hole in rows of 0,70 m. The genetic studies were realized with based on the means and variances, with help of the Program Genes. The comparison of means between the populations with simple inflorescence and with composite inflorescence was made using the “t” test with the degrees of freedom obtained by the approach of Satterthwaite. The complete model was enough to explain the observed variation in the characters related to production and peduncle. The additive effect was the more important in the genetic control for most of the characters, suggests are useful in the selection for increased of the production. The heritabilities were low and average magnitudes, recommending that the selection is made in generations more advanced. Statisticaly were differences significant between the mean of the population with simple inflorescence and the averages of populations with composite inflorescence for the characters under study.
O feijão-caupi é uma das principais fontes de proteína vegetal, para as populações de menor poder aquisitivo da Ásia, África, Europa e Américas do Norte, Central e do Sul. Nas regiões Norte e Nordeste do Brasil, representa uma das leguminosas mais importantes da dieta alimentar. A maioria dos genótipos cultivados em todo o mundo possui inflorescência simples. Contudo, foram encontradas cultivares com inflorescência composta. O objetivo deste trabalho foi estudar a herança dos caracteres relacionados à produção e à inflorescência em cruzamentos entre genótipos com inflorescência simples e inflorescência composta. O trabalho foi realizado na Embrapa Meio-Norte, em Teresina, PI, nos anos de 2006 a 2007. Foram feitos dois cruzamentos entre TVx 5058-09C (P2) x Cacheado-roxo (P1) e Cacheado-roxo (P1) x AU94-MOB-816 (P3). O genitor Cacheado-roxo com inflorescência composta e os outros dois genitores apresentam inflorescência simples. Os genitores, as gerações F1’s, F2’s e os respectivos retrocruzamentos foram avaliados quanto aos caracteres relacionados à produção e à inflorescência em um experimento em blocos casualizados com seis repetições. Os genitores e as F1’s constaram de uma parcela por bloco; as gerações F2’s e os retrocruzamentos constaram de cinco e duas fileiras por bloco,respectivamente. As parcelas foram representadas por uma fileira com 7,0 m de comprimento, o espaçamento entre fileiras foi de 1,0 m e entre covas dentro da fileira de 0,70 m. Os estudos genéticos foram realizados com base nas médias e variâncias com auxilio do Programa Genes. A comparação de médias entre as populações com inflorescência simples e composta foi feito utilizando-se o teste ‘’t’’ com o grau de liberdade obtido pela aproximação de Satterthwaite. O modelo completo foi suficiente para explicar a variação observada nos caracteres relacionados à produção e ao pedúnculo. O efeito aditivo foi o mais importante no controle genético para a maioria dos caracteres, sendo úteis na seleção para aumento da produção. As herdabilidades foram de baixa e média magnitudes, recomendando-se que a seleção seja feita em gerações mais avançadas. Estatisticamente, houve diferenças significativas entre as médias das populações com inflorescência simples e as das populações com inflorescência composta para os caracteres em estudo.

Dans un contexte de changements planétaires, l'utilisation d'agro-ressources dans les matériaux composites est une solution alternative à l'exploitation des ressources fossiles. Le développement d'agromatériaux contenant des végétaux enrobés nécessite de prendre en compte la disponibilité spatiale et temporelle des matières premières biosourcées, leur interchangeabilité et les conséquences sur les propriétés fonctionnelles résultantes. Face à la diversité des données à disposition, à la difficulté d'établir les relations de cause à effet et à la nécessaire gestion de l'imprévu, un système fiable et durable est nécessaire afin de produire un composite contenant un végétal enrobé avec une production à efficacité constante. Les méthodes d'intelligence artificielle doivent permettre d'améliorer la compréhension et le contrôle de la production liée aux matériaux concernés. Étant donné l'incertitude et la variabilité des données, nous avons appliqué l'apprentissage automatique et l'intelligence artificielle pour prédire les paramètres des expériences de manière dynamique. Un modèle pourra ainsi s'adapter en fonction des données d'apprentissage. Les prédictions sont dynamiques et les résultats sont influencés par les données. Le composite végétal est étudié sous trois aspects : prédiction de la résistance à la compression du composite, prédiction de la résistance à la flexion du composite et création d'un modèle de simulation afin de prédire les paramètres de test de résistance à la compression du composite. Le développement du composite végétal nécessite de prendre en compte les paramètres spécifiques des matières premières bio-sourcées tels que la disponibilité temporelle, l'interchangeabilité, et les conséquences sur les propriétés fonctionnelles résultantes. L'optimisation des composites végétaux peut être considérée comme un problème complexe lié à différents domaines tels que la biologie, la physico-chimie et l'ingénierie des procédés. L'optimisation et la production durables de matériaux végétaux nécessitent également une gestion de la localisation, la centralisation et la consolidation des sites de la chaîne d'approvisionnement. Les problèmes de la chaîne d'approvisionnement sont principalement la localisation des sites de production, le cheminement, l'ordonnancement, le stockage des matières premières, la distribution finale et la commercialisation. Le regroupement, la consolidation ou le clustering font référence à l'acte de fusionner deux ou plusieurs sites de supply-chain. Cela implique une réduction du nombre de centres existants. Afin de maintenir l'efficacité continue des chaînes d'approvisionnement et de production, chaque site doit offrir l'ensemble des services qui étaient servis par les sites remplacés. Le problème du regroupement peut se situer à tout niveau de la supply-chain. Le problème du k-clustering peut être défini dans une des deux parties de la chaîne d'approvisionnement qui sont en relation directe. Cette thèse a pour but de traiter la complexité rencontrée pour optimiser le composite végétal et assurer la durabilité des centres d'approvisionnement, de production et de commercialisation. Le premier objectif est atteint en optimisant les caractéristiques du matériau composite à l'aide de l'intelligence artificielle et est détaillé en première partie. Le second objectif est exposé dans la deuxième partie de cette étude. Il s'agit de la fusion des sites de la chaîne d'approvisionnement en utilisant la méthode du K-clustering. Différentes méthodes de solution d'optimisation sont proposées. L'approche transversale appliquée permettant la mise en œuvre de plusieurs compétences est présente dans l'unité de recherche EPROAD. Les méthodes proposées sont issues du domaine de l'intelligence artificielle, de la modélisation discrète issue des mathématiques appliquées, de l'analyse de sensibilité, et du domaine du génie des procédés pour le développement de méthodes coopératives intelligentes
In the context of global changes in the world, the use of vegetal resources in composite materials is an alternative solution to the exploitation of fossil resources. However, the development of the vegetal composite requires taking into account the time and space availability of bio-sourced raw materials, their interchangeability, and their consequences on resulting functional characteristics. Optimization of the vegetal composite faces a variety of available data, the complexity to establish cause and effect relationships, and the mandatory handling of unexpected events (such as disaster, crises, break down, etc, ...). Thus, a reliable and sustainable system is required in order to produce the vegetal composite with constant efficiency. Artificial intelligence methods should allow improving the understanding and control of the production related to the concerned materials. Considering the uncertainty and changeability of the data related to the vegetal materials, we applied machine learning and artificial intelligence methods to predict the parameters of the experiments dynamically. A model can adapt itself based on the training data. Predictions are dynamic, and the results are data-oriented.Herein, the vegetal composite is studied with three aspects: to predict the compressive strength of the composite, to predict the flexural strength of the composite, and a simulation model to predict the parameters of the compressive composite strength test. To overcome the mentioned problems, artificial intelligence and machine learning methods are suggested as a solution that learns from the old data in order to converge towards better local optima. The development of the vegetal composite requires taking into account the specific parameters of the bio-sourced raw materials such as temporal availability, interchangeability, and the consequences on the resulting functional properties. Optimization of the vegetal composites can be viewed as a complex problem related to different domains such as biology, physico-chemistry, and process engineering. The sustainable optimization and production of the vegetal materials also require the localization, centralization, and consolidation of the supply chain sites. The supply chain problems consist of localizing the production sites, routing, and scheduling, and storage of raw materials, and final distribution and marketing. Regrouping, consolidating or clustering are referred to the act of merging two or more sites. It is the act of reducing the number of existing centers. In order to keep the continuous efficiency in the supply and production chains, each site has to provide the whole services that used to be served by the replaced sites. The regrouping problem can be seen in any part of this chain. The k-clustering problem can be defined in any of the two parts of the supply chain that are in direct relations. This thesis aims to deal with the complexity encountered to optimize the vegetal composite and to ensure the sustainability of the supply, production, and marketing sites. The former is achieved, in the first part, by optimizing the characteristics of the composite material using artificial intelligence methods. The latter is presented in the second part of this study. The proposed method merges the supply chain site(s) using the K-clustering problem. Different optimization solution methods are proposed. The applied transversal approach allowing the coupling of skills is presented within the research unit EPROAD. The proposed methods are from the field of artificial intelligence, combinatorial optimization, discrete modeling resulting from applied mathematics, sensitivity analysis, and the field of process engineering for the development of intelligent cooperative methods

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Capes
O presente trabalho tem como objetivo o estudo teórico/experimental da sorção de água em compósitos poliméricos reforçados com fibras de macambira (Bromélia Laciniosa). Foi utilizado como matriz polimérica uma resina de poliéster insaturado e fibras de Macambira originárias do cariri paraibano. Os compósitos foram confeccionados com 70% de poliéster e 30% de fibras cortadas em tamanhos de aproximadamente 3 cm. Os ensaios de sorção de água foram realizados com amostras de 3 mm e 6 mm de espessura nas temperaturas de 25, 50 e 70°C. Uma modelagem matemática tridimensional transiente foi usada para predizer a transferência de massa durante a sorção de água destes compósitos. A cinética de sorção de água nos compósitos mostrou ser influenciada pela sua relação área/volume. Verificou-se que em tempos curtos, aproximadamente 50 horas, e temperatura de processo mais elevadas, os corpos com maior relação área/volume apresentam uma maior velocidade de sorção. Em tempos longos, os compósitos com maior relação área/volume e maior temperatura de processo apresentam maiores teores de água sorvida. O teor de umidade de equilíbrio dos compósitos com 30% de fibras de Macambira apresentaram valores de 16,8%, a 25°C, 17,00% a 50°C e 19,10% a 70ºC, para as espessuras de 3 mm, e de 12,5% a 25°C, 15,8% a 50°C e 14,8% a 70ºC, para a espessura de 6 mm. Resultados teóricos do teor de umidade médio dos compósitos foram comparados com dados experimentais e um bom ajuste foi obtido. Desta comparação, os coeficientes de difusão de massa foram obtidos para cada condição experimental.
This reseach aims to study theoretically and experimentally water absorption in polymer composites reinforced with macambira fiber (BromeliaLaciniosa). As polymer matrix was used unsaturated polyester resin and macambira fiber from cariri region of the Paraiba state. The composite samples were manufactured with 70% polyester resin and 30% macambira fiber (3cm length). Experiments were carried out in samples with 3 and 6 mm thickness at the temperatures 25, 50 and 70ºC. A transient 3D mathematical model was used to predict mass transfer during water sorption of the composites. It was verified that the water sorption kinetic is affected by area /volume relationships. For short time, approximately 50 h, the sample with lower area/volume relationships and higherprocess temperature presents a larger water absorption velocity, and for long times, these samples presents higher equilibrium water content. Equilibrium moisture content of the samples were 16.8% at 25ºC, 17.00%. at 50ºC and 19.10% at 70ºC, for 3 mm thickness, and 12.5% at 25ºC, 15.8% at 50ºC and 14.8% at 70 ºC, for 6 mm thickness. Predicted results of the moisture content of the composites were compared with experimental data, and a good agreement was verified. From this comparison diffusion coefficients were obtained for different experimental conditions.

A presente tese apresenta a utilização da fibra da casca do coco verde como reforço de matriz cimentícia para produção de fibrocimentos. Embora orgânico, o resíduo do coco verde apresenta difícil degradação e diminuí da vida útil de aterros sanitários e lixões. Para viabilizar o uso do resíduo do coco verde (fibra), como reforço de compósitos, optou-se por realizar tratamentos físico-químicos nas fibras e, substituir parcialmente o cimento Portland por material pozolânico de alta reatividade (cinza da casca de arroz (CCA)) para diminuir o ataque alcalino da matriz sobre a fibra vegetal. O experimento foi dividido em duas etapas, a primeira avaliou a fibra de coco verde com e sem tratamentos e os compósitos produzidos com elas. A segunda etapa analisou a influência de diferentes níveis de substituição do cimento Portland pela cinza da casca de arroz (CCA). Para preparação dos compósitos foi utilizada a técnica de dispersão das matérias-primas em solução aquosa, seguida de drenagem e prensagem, como uma simulação simplificada do processo Hatschek de fabricação industrial. Os compósitos foram analisados aos 28 dias (período de cura úmida) e após os processos de envelhecimento, 100 ciclos de imersão-secagem e 28 dias em banho térmico (65°C). Ensaios físicos e mecânicos avaliaram o desempenho, a resistência e a ductilidade dos compósitos. A termogravimetria permitiu observar o consumo da portlandita e a queda da alcalinidade da matriz com 50% de substituição do cimento Portland pela CCA, sem afetar a resistência do material. Os resultados obtidos indicam que a fibra do coco verde tem grande potencial para ser utilizada como reforço de fibrocimentos, desde que seja incorporada a uma matriz de alcalinidade reduzida.
This thesis studies the use of green coconut fiber as a reinforcer in the matrix cement for the production of fibre-cement. Besides being an organic material, the green coconut residues are not easily degradable, but can reduce the landfills lifespan. To evaluate the possibility of use of coconut residue fiber, as reinforcer in composites, physical-chemical treatments were carried out on the fibers, and partially replacing Portland cement with pozzolanic materials for high reactivity (rice husk ash (RHA)) was also added to decrease the alkaline attack matrix on the plant fiber. The experiment was divided into two stages: the first assessed the green coconut fiber with and without treatment and the composites produced with them. The second stage examined the influence reinforcer high reactivity to allow the use of coconut fiber as reinforcement in cementitious matrix. In the preparation of the composites, the technique of dispersing the materials in aqueous solution was used, followed by draining and pressing, as a simplified simulation Hatschek process of industrial manufacture. The composites were analyzed after 28 days and after an aging process, with 100 cycles of immersion-drying or heating in water for 28 days at 65°C). Physical and mechanical tests were used to e valuated the performance, traction resistance and ductility of the composites. A thermogravimetry test allowed the observation of the use of portlandita and the alkalinity reduction of the matrix with the addition of RHA, without affecting the resistance of the material. The results obtained indicate that the green coconut fiber has great potential to be used as a fibre-cement reinforcer, as long it is included in a matrix with reduced alkalinity.

Orientadores: Antonio Ludovico Beraldo, Holmer Savastano Jr
Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Agricola
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Resumo: A grande quantidade de resíduos agro-industriais, aliada à proibição do uso do amianto e à necessidade de solucionar problemas ambientais decorrentes do depósito e/ou queima destes resíduos, impulsionam a pesquisa para o desenvolvimento de compósitos fibro-vegetais-cimento. A durabilidade desses compósitos é um dos fatores mais importantes para a colocação deste material no mercado consumidor. Existem várias pesquisas desenvolvidas ou em andamento, algumas propondo o tratamento químico das fibras vegetais, outras fazendo uso de produtos que alterem a composição da matriz cimentícia. A utilização de polímeros em concreto e argamassa, com o objetivo de melhorar sua durabilidade é cada vez mais freqüente e a característica de certos polímeros de melhorar a aderência entre fibra e matriz, além de reduzir a capacidade de absorção de água, pode vir a melhorar a durabilidade desses compósitos. Este estudo visou a caracterização de propriedades físicas e mecânicas de compósito biomassa vegetal-cimento modificado com polímeros e a análise da durabilidade desse compósito. Foi testado um polímero de base acrílica em dois tipos de compósitos: um executado com polpas celulósicas (de Eucalipto e da reciclagem de papel jornal) e outro executado com resíduo de Pinus caribaea. Foram realizados ensaios de envelhecimento acelerado por meio de ciclos de imersão em água e secagem, e por imersão em água quente, além do processo de envelhecimento natural, por exposição dos corpos-de-prova às intempéries. As propriedades físicas do compósito avaliadas foram: a massa específica, a absorção total de água por imersão e o índice de vazios. As propriedades mecânicas avaliadas foram determinadas por meio de ensaios de resistência à tração na flexão analisando-se a tensão e a energia de ruptura; também foi determinado o módulo de deformação dinâmico, com auxílio de ultra-som. O microscópio eletrônico de varredura permitiu constatar a modificação da característica morfológica do compósito com a adição do polímero e o estado das fibras dentro do compósito ao longo do tempo. O uso do polímero melhorou o desempenho mecânico do compósito nas primeiras idades, além de promover uma significativa redução da capacidade de absorção de água, denotando sua adequação para aumentar a durabilidade do compósito
Abstract: Several researches on vegetal-fiber-cement composites have been developed aiming to solve problems related to the banishment of asbestos and environmental damages due to deposition or burnirng of agro-industry residues. The durability of the cellulose-cement composites is a key factor to introduce such material in the market. Several researches have been developed aiming to avoid the degradation of vegetable fiber-cement, some of them using chemically treated fibers and others modifying the matrix. Polymers have been used in concrete and mortar production to increase the durability. Composite degradation can be controled by polymers that modify the fiber-matrix bond and the amount of water absorption. The goal of this work was to characterize the physical and the mechanical properties of cellulose-cement composites modified by a polymer and to evaluate the subsequent durability of these materials. The dispersion of an acrylic based polymer was evaluated with two types of composites: one with cellulose pulps (Eucalyptus and wastepaper) and another with Pinus caribaea particles. The physical properties under observation were water absorption by immersion, apparent void volume and bulk density. The mechanical properties of toughness and modulus of rupture were determined by flexural test. The dynamic elasticity modulus was obtained by ultrasonic method. Samples were subjected to natural aging tests and to accelerated-aging tests by repeated soak and dry cycles and warm-water immersion. By the range of composites analyzed, the use of the polymer improves the initial mechanical properties of composites and promotes a significant decrease of the water absorption. The scanning electron microscopy (SEM) allowed to verify the modification of the morphologic characteristic of the composite with the polymeric addition and the preservation of the fibers along the time. The use of the polymer improved the mechanical performance of the composite in the first ages, besides promoting a significant reduction of the capacity of absorption of water, denoting its adaptation to increase the durability of the composite
Doutorado
Construções Rurais e Ambiencia
Doutor em Engenharia Agrícola

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This paper aims to present the feasibility of using a composite using discarded material from the cultivation of banana tree (pseudostem), which is fibrillated together with synthetic resin replacing glass fiber to be used in structural elements that do not demand large mechanical stress such as reservoirs, troughs, domes, sewage pipes etc.. For this, there were studies about the mechanical properties of a composite made with polyester resin and fiber of banana tree (Musa sp, musac), in which the splints were removed from the pseudostem, being made fibrillation by hand, with the aid of a brush steel, followed by natural drying. After treatment for cleaning and removal of wax, the fiber was cut into pieces of approximately 60 mm to 100 mm, for, together with synthetic resin, make cards of a features fiber composite with random orientation relative to the weight of the resin. We used three different percentages of fiber (3%, 6% and 9%), in order to make a comparative study between them and what would be the one with the best performance. Were manufactured specimens of each material and then subjected to uniaxial tensile tests, three point bending, moisture absorption and thermal characteristics. The results show that, in general, the use of banana tree fiber is feasible simply by an improvement in the production process (machining of the procedure) and greater care in the manufacture of parts
Este trabalho tem como objetivo apresentar a viabilidade de um comp?sito utilizando material descartado da lavoura da bananeira (pseudocaule), o qual ? fibrilado juntamente com resina sint?tica em substitui??o ? fibra de vidro, a ser utilizado em elementos estruturais que n?o demandem grandes esfor?os mec?nicos, tais como reservat?rios, calhas, domos, tubula??es de esgotamento etc. Para isso foram efetuados estudos sobre as propriedades mec?nicas de um comp?sito de resina poli?ster e fibra de bananeira (musa s.p., mus?cea), nos quais foram retiradas as talas do pseudocaule, sendo feita a fibriliza??o de forma manual, com o aux?lio de uma escova de a?o, seguido de secagem ao natural. Ap?s tratamento para limpeza e retirada de cera, a fibra foi cortada em peda?os de aproximadamente 60 mm a 100 mm para, juntamente com a resina sint?tica, fabricar placas de um comp?sito de caracter?sticas fibrosas com orienta??o aleat?ria em rela??o ao peso da resina. Foram utilizadas tr?s percentagens distintas de fibras (3%, 6% e 9%), a fim de se efetuar um estudo comparativo entre elas e determinar qual seria aquela com o melhor desempenho mec?nico. Foram fabricados corpos de prova de cada material, sendo ent?o submetida aos ensaios de tra??o uniaxial, flex?o em tr?s pontos, absor??o de umidade e caracter?sticas t?rmicas. Os resultados demonstram que, de forma geral, o uso de fibra de bananeira ? vi?vel, bastando uma melhoria no seu processo de obten??o (mecaniza??o do procedimento) e um maior cuidado durante a fabrica??o das pe?as

Depuis des millénaires, le chanvre est cultivé pour ses fibres. Longues et résistantes, elles peuvent notamment entrer dans la composition de matériaux textiles et composites, secteurs industriels en plein essor. Cependant, leur manque d’homogénéité et la complexité de leur affinage ne leur permettent pas encore d’être compétitives face aux fibres synthétiques ou de coton. Mais des fibres de chanvre fines pourraient être produites à partir de fibres brutes en utilisant un traitement par explosion à la vapeur à bas coût, faible consommation d’énergie et avec un faible impact environnemental. Une caractérisation morphologique, chimique et mécanique des fibres a été réalisée avant et après traitement dans le but d’optimiser les paramètres de ce procédé, selon une méthodologie de plan d’expériences. Ces essais ont montré que l’explosion à la vapeur pouvait être utilisée pour produire des fibres correspondant aux critères imposés par l’industrie textile et des matériaux composites. Des éléments ont aussi été apportés sur une éventuelle industrialisation de l’explosion à la vapeur. Là encore, les résultats montrent que ce procédé pourrait être industriellement compétitif en termes de coûts, de consommation en eau et en énergie, et de rendements. Enfin, des fibres ont été produites à partir de sols pollués contenant des métaux lourds. Les teneurs en métaux dans les différentes parties de la plante et dans les fibres ont été mesurées avant et après explosion à la vapeur. Les résultats obtenus ouvrent de nouvelles perspectives quant à un usage durable de Technosols (notamment des friches industrielles) pour la production de fibres de chanvre à usage industriel
Hemp plants have been cultivated for their usable fibers for thousands of years. The fibers are long and resistant and can be utilized for creation of textile and composite materials, relevant to burgeoning industrial sectors. However, due to their lack of homogeneity and the complexity of their refining, hemp fibers are unable to compete with synthetic and cotton fibers. But fine hemp fibers could be successfully produced from technical fibers using a steam explosion treatment at a low cost, a low energy consumption and with a low environmental impact. To optimize the parameters of this process, a morphological, chemical, and mechanical characterization was performed before and after steam explosion using a design of experiments methodology. These experiments showed that this process can be used to produce hemp fibers with the standards defined by the textile and composite materials industries. Some features have also suggested some prospects in the industrialization of steam explosion for fibers production. These results showed that this process could be industrially competitive in terms of costs, water and energy consumption and yield. Finally, phytoremediation-borne hemp fibers were produced from soils contaminated with trace elements. The metals concentrations in plant components and in the fibers were measured before and after steam explosion treatment. The results offer new insights and prospects for a sustainable use of Technosols (in particular brownfield sites) by the production of hemp fibers

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CNPq
O presente trabalho tem como objetivo o desenvolvimento de compósitos poliméricos reforçados com fibras de Caroá Neoglaziovia variegata para avaliação de seu desempenho mecânico, bem como suas características de sorção de água. Foi utilizado como matriz polimérica uma resina de poliéster insaturado e fibras de Caroá originárias do cariri paraibano. Os compósitos foram confeccionados com diferentes teores de fibras, cortadas em tamanhos de aproximadamente 3 cm, e moldados por compressão em molde metálico para avaliação das propriedades mecânicas. A composição de amostras de melhor desempenho mecânico foi escolhida para os ensaios de sorção de água, com amostras de 20x20mm² com 3cm e 6cm de espessura na temperatura de 25°C, 50°C e 70°C. Uma modelagem matemática tridimensional transiente foi usada para predizer a transferência de massa durante a sorção de água destes compósitos. Os resultados indicam que as propriedades mecânicas em tração dos compósitos estudados aumentam com o teor de fibras acima de 24% em massa até um volume crítico, em torno de 30%.Resistência ao impacto aumentou para todas as composições em virtude da eficiência de transferência de tensão para as fibras. Os resultados obtidos para o módulo de elasticidade dos compósitos evidenciam que estes são superiores ao da matriz, para todos os teores abaixo de 45% de fibras, o que é associado às características das fibras. A cinética de sorção de água nos compósitos mostrou ser influenciada pela relação área/volume. Pôde-se observar que em tempos curtos, aproximadamente 100 horas, os corpos com menor relação apresentam uma maior velocidade de sorção. Em tempos longos os compósitos com maior relação área/volume apresentam maiores teores de água sorvida. O teor de umidade de equilíbrio dos compósitos com 30% de fibras de caroá apresentaram valores de 14,48% à 25ºC e 16,52% à 70ºC, para as espessuras de 3 e 6 mm, respectivamente. A modelagem matemática utilizada para a obtenção da solução numérica de sorção de água nos compósitos reforçados por fibras de caroá foi adequada e satisfatória e a técnica de volumes finitos mostrou-se eficiente para discretizar a equação de difusão no sistema de coordenadas cartesianas para um sólido paralelepípedo, possibilitando a análise de fenômenos difusivos transientes nestes sólidos.
This research has the objective of developing polymeric composites enhanced with Caroá fibers Neoglaziovia variegata, in order to evaluate its mechanical performance and water sorption. It was used as polymeric matrix an unsaturated polyester resin and Caroá fibers originated from Paraiba state. The composites were made with different fiber contents, cut approximately with 3cm length and molded by compression in a metallic mould in order to evaluate its mechanical properties. The better mechanical composition of the sample was chosen to water sorption test in sample with dimension 20x20mm² and 3cm and 6cm thickness in the temperature of 25°C, 50°C and 70°C. A tri-dimensional transient mathematical modeling was used to predict mass transfer during the water sorption by these composites. Results indicates enhancement of mechanical properties of composites with 24% of mass made of the fibers until a critical volume of 30%. For the impact resistance this increases occurred for all compositions because of the transference of tension for the fibers. The results for elasticity modulus of composite shows that are higher than to the matrix for all fiber contents lower than 45%, which is related with the fiber properties. The water sorption kinetic was related with the area/volume relationship. We can observe that in short period of time, 100 hours, that composites with lower area/volume relationship absorbs water faster. On the order hand, the ones with higher area/volume relationship show more sorption in longer periods of time. The equilibrium moisture content for 30% fiber composite show results of 14.48% in 25°C and 16.52% in 70°C, for 3mm and 6mm thickness respectively. Mathematical models used to obtain numerical solution of water sortion in composites enhanced with Caroá fibers were satisfactory and the finite volume techniques was adequated to discretize the diffusion equation in Cartesian coordinate system for a parallelepiped solids, permitting the analyze of transient diffusive phenomena in this solids.

Os compósitos são materiais formados por duas fases de diferentes propriedades químicas e físicas, sendo uma matriz e um reforço, que apresentam alta rigidez, melhores respostas à fadiga sob cargas cíclicas, leveza e resistência mecânica, o que os torna viáveis para substituir materiais nobres e de custo elevado, com diversas aplicações na aeronáutica, nos esportes, na indústria bélica e principalmente na construção civil. Além disso, os compósitos podem ser obtidos a partir da incorporação de resíduos em sua composição, solucionando problemas como o descarte irregular. Com o intuito de contribuir nessa área de conhecimento o presente estudo propôs o desenvolvimento de um compósito em forma de placas poliméricas a partir da incorporação do agregado reciclado de poliuretana termofixa reciclado à resina vegetal de mamona e à mantas de fibra de vidro. Para isso, o trabalho estabeleceu uma metodologia na qual o resíduo industrial de poliuretana termofixa é transformado em agregado reciclado, a partir de processos de corte e moagem, caracterização e classificação segundo as normas NBR 10.004 a 10.007 (ABNT, 2004). Na sequência, com o auxílio de uma prensa térmica, foi possível confeccionar as placas poliméricas e caracterizálas quanto às suas propriedades mecânicas (tração, flexão, punção), físicas (absorção em água, inchamento, densidade e dureza), térmicas (condutividade térmica) e quanto ao seu potencial de durabilidade (resistência ao impacto, à abrasão superficial, ao ataque químico, à exposição ao ultravioleta e às intempéries, resistividade elétrica e flamabilidade). Os resultados obtidos por meio dos ensaios realizados apontaram que os parâmetros ensaiados comportaram-se como materiais semelhantes àqueles utilizados na construção civil, o que possibilita a utilização do material desenvolvido nesta pesquisa em aplicações por este setor.
This study proposes the development of a composite material in the form of polymer slabs. The material is created from the incorporation of recycled thermoset polyurethane to castor oil resin and glass fiber mats. Composite materials are formed by two phases with different chemical and physical properties. One phase is a matrix, and the other a reinforcement. These materials are highly stiff, light, have mechanical strength and present better responses to fatigue under cyclic loads. These properties make them a substitute for noble materials, being eligible for uses in aviation, sports, the arms industry and, specially, civil construction. Furthermore, composites may be obtained by the incorporation of residue, solving problems of waste disposal. In the procedures undertaken, the industrial waste of thermoset polyurethane is transformed into a recycled aggregate, achieved by the cutting, grinding, characterization and classification in compliance to the ABNT standards (NBR 10.004 to10.007). Afterwards, with the use of a thermal press, it was possible to produce the slabs and characterize them according to the following properties: mechanical (tensile strength, and puncture), physical (water absorption, swelling and stiffness), thermal (conductivity) and the potential durability (resistance to impact, abrasion, chemical attack. ultraviolet and weather exposure, electrical resistance, and flammability). The test results indicated that the composite behaves similarly to materials used in civil construction, which enables its use in the area.

Efficient processing of vegetal biomass is a great challenge to current research studies. This work is focused on improving the yield of enzymatic hydrolysis of wood residues by removal of lignin using a alkaline wash assisted by microwave heating. The treatments were carried out for one hour in a pressurized microwave reactor (Synthwave-Milestone). The performance of the treatments was assessed by monitoring the concentration of lignin (determined by UV absorbance at 320 nm against a calibration curve). Each experiment was carried out in duplicate. The treatment conditions were established according to an experimental matrix constructed (in Design Expert 11) after the careful selection of the most important factors that affect the lignin removal from wood residue: concentration of NaOH solution, liquid to solid ratio and temperature. A central composite design was constructed with the independent factors mentioned above. ANOVA indicated adequate fitting of the model (correlation coefficient R2=0.95). The exploration of the experimental space (figure 1) with the fitted model indicates the dominant effect of temperature as independent factor. Optimization of experimental conditions within the experimental space was carried according to the following criteria: minimization of temperature, liquid to solid ratio and NaOH concentration and maximization of the response variable, the lignin concentration. The optimal solution (141 mg lignin / g dry wood residue) proposed by the model for these optimization criteria indicates a point in the region determined by the following coordinates: 0.4M NaOH, 1070C and a ratio of liquid to solid equal to 50. Fig. 1. 3D plot of lignin responses surfaces function of the independent factors with significant effectsAcknowledgment The authors acknowledge the financial support received from Competitiveness Operational Program 2014-2020, Priority axis 1, Project No. P_36_611, MySMIS code 107066, Innovative Technologies for Materials Quality Assurance in Health, Energy and Environmental - Center for Innovative Manufacturing Solutions of Smart Biomaterials and Biomedical Surfaces – INOVABIOMED.