In recent decades, the necessity to find a completely environmentally friendly substitute for synthetic fibres in composite applications has intensified, driven by the objective of reducing emissions in both the production and disposal of composite components. Natural fibres present a potential solution, yet they have some issues such as the inhomogeneous quality of their cross-section and mechanical properties, depending on different aspects, for example, growing conditions and the amount of intake water. Another potential solution is organic man-made fibres, such as fibre made from Cellulose NanoFibrils, which do not present the previously cited drawbacks.This thesis investigates and compares the potentials of organic fibres, either man-made or natural, in composite reinforcement applications. To accomplish this, organic fibres are integrated into composite plates using two distinct thermoset matrices, epoxy and vinyl ester, respectively via methods of hot pressing and vacuum infusion. Subsequently, the produced composite plates undergo tensile testing, with the results being compared with the theoretical values. Furthermore, microscopy is employed to examine the adhesion at the interface between reinforcement and matrix.The findings indicate that man-made fibres from Cellulose NanoFibrils bind more efficiently with thermoset matrices compared to flax fibres, making them more adept as reinforcement materials for thermoset composites. / Under de senaste decennierna har behovet av att hitta en helt miljövänlig ersättning för syntetiska fibrer i kompositapplikationer intensifierats, drivet av målet att minska utsläppen både vid produktion och avfallshantering av kompositkomponenter. Naturliga fibrer presenterar en potentiell lösning, men de har vissa problem som den ojämna kvaliteten på deras tvärsnitt och mekaniska egenskaper, beroende på olika aspekter, till exempel växtförhållanden och mängden intaget vatten. En annan potentiell lösning är organiska konstgjorda fibrer, som fibrer tillverkade av cellulosa nanofibriller, som inte har de tidigare nämnda nackdelarna.Denna avhandling undersöker och jämför potentialen hos organiska fibrer, antingen konstgjorda eller naturliga, i kompositförstärkningsapplikationer. För att uppnå detta integreras organiska fibrer i kompositplattor med hjälp av två olika termohärdande matriser, epoxi och vinyl-ester, via metoder för varmpressning och vakuuminfusion. Därefter genomgår de producerade kompositplattorna dragprovning, med resultaten jämförda med de teoretiska värdena. Dessutom används mikroskopi för att undersöka vidhäftningen vid gränssnittet mellan förstärkning och matris.Resultaten indikerar att konstgjorda fibrer från cellulosa nanofibriller binder effektivare med termohärdande matriser jämfört med linfibrer, vilket gör dem mer lämpliga som förstärkningsmaterial för termohärdande kompositer.

[pt] Esta dissertação apresenta um debate sobre a técnica que aproveita os materiais disponíveis no local. Este debate começa pelo próprio conceito de técnica e pela ideia de progresso técnico, para se esclarecer mais sobre a natureza da técnica que estamos pesquisando. Diferentes movimentos que se relacionam à técnica que estamos pesquisando são apresentados, como a tecnologia apropriada, a permacultura e a arquitetura popular tradicional. O objeto de estudo é a construção em terra crua, bambu e fibras naturais, que são os materiais pesquisados no Laboratório de Investigação em Living Design (LILD). É utilizada a metodologia prática deste laboratório e sua experiência prévia com técnicas que trabalham com estes materiais para dar prosseguimento à investigação. / [en] This dissertation presents a discussion on the technique that uses materials available on site. This discussion begins with the concept of technique and the idea of technical progress, to further clarify the nature of the technique that we are researching. Different movements that relate to the technique that we are researching are presented, such as appropriate technology, permaculture and traditional folk architecture. The object of investigation is buildings with mud, bamboo and natural fibers, which are the materials studied by the Laboratório de Investigação em Living Design (LILD). This study uses the practical methodology of the laboratory and its previous experience with techniques that work with these materials to continue the investigation.

L’étude présentée porte sur la caractérisation et la comparaison des propriétés quasi-statiques et en fatigue de composites à fibres de lin et de verre avec une matrice époxy. Une importante campagne d’essais de fatigue a été réalisée à partir des propriétés quasi-statiques de traction et cisaillement plan mesurées. Il apparaît que les caractéristiques en statique et en fatigue du verre/époxy sont supérieures à celles du lin/époxy à taux de fibres et stratification identiques. Cependant, en raison de la faible densité des renforts de lin, les écarts entre les propriétés spécifiques des deux matériaux sont faibles. La mesure de l’évolution des propriétés en fatigue a mis à jour des comportements phénoménologiques particuliers tels que la diminution de l’amortissement et l’augmentation de la rigidité des lin/époxy  ayant des fibres parallèles à la direction du chargement, au cours de la vie des éprouvettes. Le suivi de l’endommagement par la mesure des densités de fissures montre que celle-ci augmente avec le chargement et le nombre de cycles appliqués. Les simulations par éléments finis de la durée de vie des composites lin/époxy, intégrant la variabilité des paramètres du modèle par la méthode Monté-Carlo, donnent des courbes de Wöhler conservatives par rapport aux données expérimentales. Conformément aux mesures expérimentales, la variabilité des durées de vie calculées diminue lorsque le chargement baisse / The present study focuses on the characterization and comparison of the quasi-static and fatigue properties of flax and glass fibre reinforced composites with an epoxy matrix. An extensive experimental campaign of fatigue tests have been performed using the measured quasi-static tension and in plane-shear properties. It appears that the static and fatigue characteristics of the glass/epoxy composites are higher than that of flax/epoxy ones with similar fibre volume fraction and lay-ups. However, due to the low density of flax reinforcements, the differences between the specific properties of the two materials are low. The measurement of the evolution of the fatigue properties has highlighted particular phenomenological behaviours such as the decrease of the damping and the increase of the stiffness of flax/epoxy composites having fibres parallel to the loading direction, during specimens’ life. The monitoring of material damage by measuring the crack density showed its increase with the loading level and the number of cycles applied. Finite elements simulations of the life cycle of flax/epoxy composites, incorporating the variability of the model’s parameters by Monte Carlo method, gave conservative Wöhler curves compared with experimental data. In agreement with the experimental measurements, the variability of lifetimes calculated decreases when the load decreases

[pt] O objetivo deste trabalho foi avaliar as propriedades mecânicas, físicas e microestruturais de materiais compósitos cimentícios reforçados por fibras naturais e de laminados de bambu. O trabalho experimental foi direcionado para a determinação da tenacidade. Para se determinar a tenacidade foram utilizados três tipos de ensaios: impacto Charpy, impacto balístico e flexão em 3 pontos. Após os ensaios, a superfície de fratura dos corpos-de-prova foi analisada por microscopia eletrônica de varredura (MEV). Esta análise microestrutural serviu para determinar os modos de fratura e validar as hipóteses feitas nos modelos matemáticos utilizados. Foram usados modelos adaptados da literatura para a determinação da tenacidade e os valores teóricos obtidos foram confrontados com os experimentais. Determinou-se também através de modelos encontrados na literatura a tensão interfacial de todas as fibras utilizadas nesta pesquisa. Os modelos empregados para calcular a tenacidade e a tensão de adesão interfacial, se mostraram eficientes e válidos. Em segundo plano, porém não menos importante, ficou a determinação das propriedades térmicas dos materiais utilizados. Foram efetuados ensaios de condutividade térmica do compósito e ensaios termogravimétricos das fibras vegetais e do bambu. Os compósitos cimentícios foram reforçados por diferentes fibras naturais: polpa refinada de bambu (CPB), polpa de sisal (CPS), polpa de eucalipto (CPE), fibras curtas de sisal (CPFS) e wollastonita (CPW). As proporções das polpas de bambu, sisal e eucalipto utilizadas como reforço nas matrizes cimentícias foram de 8 por cento e 14 por cento em relação à massa do cimento, a da fibra curta de sisal (25 mm) foi de 3 por cento em relação ao volume e a da wollastonita foi de 11,5 por cento em relação à massa. Compóstios híbridos feitos com wollastonita e polpa de bambu (CPBW) foram também produzidos apenas variando a proporção da polpa de bambu em 8 por cento e 14 por cento e mantendo fixa a da wollastonita em 11,5 por cento. Como uma tentativa de se melhorar a resistência ao impacto, laminados CPB/AL foram também fabricados colando duas chapas de alumínio (liga 5052 H34) de espessura 0,8 mm em ambas às faces dos compósitos reforçados por fibra de bambu, formando assim compósitos sanduíche (CPBA). O bambu Moso (Phyllostachys heterocycla pubescens) com 5 anos de idade foi usado para fabricação dos laminados de bambu, sendo tratado com água fervida para a prevenção de ataques biológicos. Técnicas para a extração do laminado a partir de seu formato natural foram estudadas estabelecendo suas vantagens e desvantagens. Para o ensaio de impacto foram utilizados corpos-de-prova com dimensão nominal de 120 mm x 15 mm x 6 mm perfazendo um total de 18 corpos-de-prova. Para o de flexão foram realizados ensaios com uma lâmina simples de bambu (BL) e bambu laminado colado (BLC) com 3 camadas de lâminas dispostas ortogonalmente. Os resultados dos testes de impacto Charpy e flexão em 3 pontos comprovaram a boa tenacidade do bambu laminado quando submetido a cargas de impacto (42,54 kJ/m2) e a cargas estáticas (19,77 kJ/m2 para o laminado e 17,63 kJ/m2 para o laminado colado). Compósitos sanduíche constituídos de alumínio e laminados de bambu foram também fabricados. Estes foram analisados através de ensaios de impacto balísticos seguindo as recomendações da norma NIJ 0101.04. Observações no microscópico eletrônico de varredura foram realizadas para se analisar os mecanismos de falha dos laminados. / [en] The main objective of this work was to evaluate the mechanical, physical and microestructure properties of cementitious composite materials and bamboo laminates. The experimental program was focused on the determination of toughness. Three diferent types of tests were performed in order to establish it: Charpy impact, ballistic impact and three point bending test. After the tests, the fractured surface of the failed test specimens was observed using a Scanning Electron Microscope (SEM) to establish the failure mode. Mathematical models adapted from the available literature were used to determine the toughness from which the values were confronted to the ones obtained experimentally. It was also determined by mathematical models the interfacial bond stress of all fibers used in this research. The two models, used in the toughness and interfacial bond stress calculation, showed to be efficient, providing valid results. In second plan, but not less important, was the determination of the materials thermal properties. Thermal conductivity tests of the composites and thermogravimetry of the fibers and bamboo were performed. The cementitious composites were reinforced by different natural fibers: refined bamboo pulp (CPB), sisal pulp (CPS), eucalyptus pulp (CPE), short sisal fibers (CPFS) and wollastonite. The mass fraction of bamboo, sisal and eucalyptus pulp studied were 8 percent and 14 percent. For the wollastonite fiber the mass fraction studied was 11.5 percent and for the short sisal fiber a 3 percent volume fraction was studied. Hybrid composites made with wollastonite and bamboo pulp (CPBW) were also produced varying the bamboo fraction mass to 8 percent and 14 percent but keeping constant to 11.5 percent the wollastonite mass fraction. The slurry de-watering process was used in the production of all composites described before. To reduce the adverse effects of weathering on the cellulose fibers and to improve the impact load and flexural resistance of the composite, aluminum thin sheets were used to produce a sandwich composite lamina with the CPB, which was denominated as CPBA. Compound Adhesive gel from Otto Baumgart which is a type of epoxy was used to fix the aluminum sheets on the CPB. The use of aluminum has proved to give much higher impact resistance results when compared to the CPB ones. The 5 years old Moso bamboo (Phyllostachys heterocycla pubescens), which was previously treated in boiled water to eliminate biological agents, was used to produce the bamboo laminates. Techniques were developed to extract bamboo laminates from its natural form, establishing its advantages and disadvantages. For the Charpy impact test, a total of 18 specimens with nominal dimensions of 120 mm x 15 mm x 6 mm were tested. Laminated (BL) and 3 layer cross ply laminated bamboo (BLC) were tested in bending. A total of 9 specimens were tested per bamboo configuration. The BL specimens had nominal dimensions of 120 mm x 30 mm x 6 mm and the BLC were 120 mm x 30 mm x 17 mm. The results demonstrated the good toughness of bamboo laminates when subject to dynamic (42.54 kJ/m2) and to static load (19.77 kJ/m2 for the laminate and 17.63 kJ/m2 for the cross ply laminate). Aluminum thin sheets were again used to make sandwich composites, but now using the bamboo laminate (BLCA). The BLCA was tested using the ballistic impact test following the standard NIJ 0101.04. Analysis on the Scanning Eléctron Microscope (SEM) were performed in order to establish the laminate s failure mechanisms.

[pt] Visando adequar a sociedade do consumo a uma existência menos impactante ao meio ambiente, a busca por materiais oriundos de fontes renováveis e passíveis de biodegradação é crescente. No entanto, para que esta transição seja mais eficiente, se faz necessário mudar não só os materiais que são produzidos, mas também a logística da produção e os processos produtivos utilizados. Com base nisto, o objetivo deste trabalho é desenvolver e caracterizar uma chapa de fibras, desenvolvida a partir de resíduos da agro indústria do palmito de pupunha (Bactris Gasipaes), a ser produzida por meio da capacitação dos agricultores locais, com processos de baixa complexidade tecnológica, baixo custo de implementação e mínimo impacto ambiental associado à sua produção. Os ensaios foram realizados de acordo a norma ABNT 15316 - 2:2009, que determina parâmetros de amostragem e métodos de ensaio das chapas de fibras de média densidade (MDF). Como adesivo, aglomerante, foi utilizada a resina poliuretana, de base vegetal, em diferentes proporções fibra/matriz. Os resultados foram analisados seguindo a norma ABNT 15316 – 3: 2009, que estabelece os requisitos para chapas de densidades diferentes, produzidas para os mais diversos fins (estrutural, geral, forro, parede, dentre outros). Dessa forma, foi possível atestar a viabilidade de produção da chapa em pequena escala, garantindo a parcial substituição das chapas MDF disponíveis no mercado, o que comprova a real oportunidade de crescimento sustentável, através da geração de renda e desenvolvimento sócio ambiental. / [en] Aiming to adapt the consumer society to a life less harmful to the environment, the research for materials produced from renewable sources and subject to biodegradation is increasing. However, for this transition to be more efficient, it is necessary to change not only the materials that are being produced but also the production logistics and production processes used. On this basis, the objective of this work is to develop and characterize a fiberboard, developed from the agro-industry waste of Pupunha`s palm heart (Bactris gasipaes), to be produced through the training of local farmers, processes with low complexity technology, low cost of implementation and minimal environmental impact associated with its production. The tests were performed according to the ABNT 15316 - 2:2009, which determines the parameters of sampling and test methods for medium density fiberboard (MDF). The vegetal based polyurethane was used as adhesive/ binder. The samples were produced in different proportions fiber / matrix. The results were analyzed following the ABNT 15316-3: 2009, which establish the requirements for plates of different densities, produced for different purposes (structural, general, lining, wall, among others). Thus it was possible to demonstrate the feasibility of a small scale production of the alternative fiberboard, ensuring the partial replacement of the medium density fiberboards usually available on the market. This points out to the growth opportunity of the rural comunitys through income generation and socio-environmental development.

This thesis examines the manufacturing process of a novel flax fibre polypropylene composite material, focusing on understanding the process and its influencing factors. The composite was manufactured using pre-impregnated twill-woven flax fibre sheets (AmpliTex 5040 – PP) as outer layers and two core layers of pre-impregnated polypropylene sheets reinforced with short, randomly oriented natural fibres (NfPP). The manufacturing process involved preheating the material to core temperatures of 180°C, 190°C, or 200°C, followed by compression moulding with tool gaps of 3.0 mm, 3.2 mm, and 3.4 mm. The study found that the core temperature after preheating did not significantly affect the composite's thickness or layer compaction. However, the tool gap exhibited a significant effect, with an increase in thickness with larger tool gaps. The lowest deviation from the tool gap size was observed at 3.2 mm. The compaction of the AmpliTex 5040 – PP layers demonstrated no dependency on the tool gap, while the NfPP layers exhibited the highest compaction at a gap size of 3.0 mm. Thermal degradation analysis indicated that flax fibre is the most critical component, with higher core temperatures reducing the ultimate tensile strength and fracture strain of the composite material. The maximum tensile properties were observed for materials preheated to 180°C during manufacturing. The manufacturing process demonstrated an improvement in reproducibility compared to previous methods, although substantial variance in thickness remained.

Steigende Leichtbauanforderungen führten in den vergangenen Jahren zu einer verstärkten Weiterentwicklung neuer Leichtbauwerkstoffe und besonders leistungsfähiger Verfahrenstechnik für die Umsetzung leichter Automobilkomponenten in Großserie. Im Fahrzeuginterieur konnten sich naturfaserverstärkte Kunststoffe erfolgreich etablieren, die in Form flächiger Wirrfaserhalbzeuge zu formgepressten Verkleidungselementen verarbeitet werden. Für die Auslegung derartiger Verkleidungsbauteile ist eine monolithische Leichtbauweise charakteristisch, bei der zur Gewährleistung erforderlicher mechanischer Eigenschaften die minimalen Halbzeugflächenmassen bauteilabhängig im Bereich 1200–1400 g/m2 liegen. Zur Erschließung weiterer Leichtbaupotenziale stellt die Anwendung der Sandwichverbundbauweise eine aussichtsreiche Leichtbaustrategie dar, die aufgrund des Fehlens anforderungsgerechter Materialkonzepte bisher kaum Berücksichtigung fand. Das Ziel dieser Arbeit ist die Entwicklung eines ganzheitlichen Leichtbaukonzepts in neuartiger Sandwichbauweise, welches die Anforderungen hinsichtlich der Formgebung und Bauteilstabilität erfüllt und eine signifikante Reduktion der Flächenmasse unter 1000 g/m2 gestattet. Die verfahrenstechnische Grundlage bildet eine neuartige durchgängige Prozesskette, wobei leichte Naturfaser-Polypropylen-Hybridvliesstoffe in Kombination mit einer Kunststoffschaumfolie in einem kontinuierlichen Prozess zu einem Sandwichhalbzeug und anschließend in automatisiertem Formpressverfahren zu einem komplex geformten Bauteil verarbeitet werden. Durch eine umfangreiche Charakterisierung der einzelnen Prozessschritte entlang der gesamten Prozesskette werden in zugehörigen Sensitivitätsanalysen optimale Fertigungsparameter ermittelt und bei der Herstellung eines Technologiedemonstrators validiert. Darüber hinaus wird am Beispiel dieses Technologiedemonstrators erstmalig ein integrativer Simulationsansatz erarbeitet, der umformbedingte lokale Änderungen der Flächenmasse und der resultierenden Werkstoffkennwerte bei der numerischen Steifigkeits- und Festigkeitsanalyse berücksichtigt. Abschließend erfolgt im Sinne einer ganzheitlichen Betrachtung die Beurteilung potenzieller Umweltwirkungen der entwickelten Sandwichverbundtechnologie sowie die Untersuchung einer verfahrenstechnischen Lösung zur stofflichen Wiederverwertung von Produktionsreststoffen und Altbauteilen.:1 Einleitung 2 Problemstellung und Zielsetzung 3 Leichtbau im Fahrzeuginterieur 4 Neues ökologisches Leichtbaukonzept für Interieur-Verkleidungselemente 5 Beschreibung der Prüfmethoden 6 Werkstoffmechanische Betrachtung einer Referenzstruktur 7 Halbzeugentwicklung und -optimierung 8 Bauteil- und Verfahrensentwicklung 9 Struktursimulation von neuartigen Mikrosandwich-Bauteilen 10 Vergleichende Ökobilanzierung 11 Stoffliche Wiederverwertungsstrategie für Altbauteile 12 Zusammenfassung / Rising lightweight requirements have led in recent years to an intensified development of new lightweight materials and high-performance processing technologies for the implementation of lightweight automotive components in a large scale production. For trim parts in the automotive interior, natural fiber-reinforced plastics in the form of nonwovens, are successfully established. To fullfill the mechanical requirements, the most common design of such parts is monolithical with an component specific area weight of the semi-finished products between 1200–1400 g/m2. A promising strategy for generating further lightweight potentials are sandwich constructions, which are currently rarely used in the automotive interior, due to the lack of suitable material concepts. The aim of this work is the development of a new sandwich-based lightweight concept, that fullfills the requirements in terms of formability and component stability, by permitting a weight reduction of the semi-finished product below 1000 g/m 2 at the same time. The part production is based on a novel process chain, where light NF-PP hybrid nonwovens are continuously processed with a polymeric foam foil to a semi-finished product, that is formed afterwards to complex parts in a compression molding process. The optimal processing parameters along the entire process chain are determined by sensitivity analyses, and validated by a technology demonstrator. In addition, the technology demonstrator will be used for the development of a novel simulation approach, where local changes of the area weight in the forming process and the resulting material properties are taken into account for a numerical analysis of stiffness and strength. Finally the potential environmental impact of the new sandwich-based lightweight technology and a possible method for material recycling are investigated.:1 Einleitung 2 Problemstellung und Zielsetzung 3 Leichtbau im Fahrzeuginterieur 4 Neues ökologisches Leichtbaukonzept für Interieur-Verkleidungselemente 5 Beschreibung der Prüfmethoden 6 Werkstoffmechanische Betrachtung einer Referenzstruktur 7 Halbzeugentwicklung und -optimierung 8 Bauteil- und Verfahrensentwicklung 9 Struktursimulation von neuartigen Mikrosandwich-Bauteilen 10 Vergleichende Ökobilanzierung 11 Stoffliche Wiederverwertungsstrategie für Altbauteile 12 Zusammenfassung