Carolina Gomes Dias Ribeiro

Flexural Behavior of Epoxy Matrix Composites Reinforced with Malva Fiber

Polymer composites reinforced with natural fibers have been increasingly investigated and applied as engineering materials owing to their economical, technical, societal and environmental advantages. The malva fiber, particularly an important resource in the Amazon region in Brazil, only recently begin to be investigated as possible composite reinforcement for engineering application. However, the mechanical properties of composites reinforced with malva fiber are still unknown. In this paper, the flexural behavior of epoxy matrix composites reinforced with continuous malva fiber was for the first time investigated. Specimens of continuous malva fibers aligned along an epoxy matrix were press-molded. Three-points bending test were performed and the fractured specimens were analyzed by SEM. The results showed a marked improvement in the composites flexural properties with the increase in the amount of reinforced malva fiber. This improvement was found to match the Rule of Mixtures, which revealed the unique potential of malva composites for engineering applications.

Pullout Tests Behavior of Polyester Matrix Reinforced with Malva Fiber

The interface between a composite matrix and the reinforcing fiber plays an important role in the efficiency by which an applied load is transmitted throughout the composite structure. The shear stress at the fiber/matrix interface can be associated with this load transference and, consequently, will affect the composite strength. In the present work, pullout tests were used to evaluate the interfacial shear stress of malva fiber in polyester matrix composites. A small critical length was found for the malva fiber embedded in polyester, which corresponds to a relatively weak fiber/matrix bond and lower interfacial strength.

Charpy Impact Tests of Epoxy Composites Reinforced with Giant Bamboo Fibers

The giant bamboo fiber is among the strongest in the Bambusa species with a potential for application as engineering material. Its properties have been evaluated but there is limited information on the impact resistance of epoxy composites incorporated with giant bamboo fibers. Therefore, this study evaluated the Charpy impact energy of epoxy matrix composites reinforced with up to 30 vol% of giant bamboo fibers. Specimens with Charpy configuration were press-molded with continuous and aligned giant bamboo fibers reinforcing a DGEBA-TETA epoxy as the composite matrix. The energy absorbed by the composites was obtained in standard impact tests and the fracture surface of ruptured specimens was analyzed by scanning electron microscopy, SEM. The impact energy was found to increase exponentially with the amount of incorporated fiber. SEM observations revealed the mechanism of crack propagation both in the brittle epoxy matrix and in the fiber interface of the composites.

Characterization of Thermal Behavior of Polyester Composites Reinforced with Curaua Fibers by Differential Scanning Calorimetry

Epoxy composites reinforced with natural lignocellulosic fibers have, in recent times, been gaining attention in engineering areas as lighter and cheaper alternatives for traditional composites such as the “fiberglass”. The curaua fiber is the one strongest today being considered as reinforcement of composites for automobile interior parts. In fact, several studies are currently being dedicated to curaua fiber composites since physical and mechanical properties are required for practical uses. In this work, the thermal behavior of epoxy composites reinforced with up to 30 % in volume of curaua fibers was investigated by differential scanning calorimetry, DSC. The results showed endothermic and exothermic events associated with water release and possible molecular chain amorphous transformation. Comparison with similar composites permitted to propose mechanism that explains this DSC thermal behavior.

Comparative Mechanical Analysis Between Epoxy Composite Reinforced with Random Short Cuarua Fibers and Aligned Long Curaua Fibers

Synthetic fibers have been used for many years to attend the demands required by the most technological fields, but their use have been questioned due to the impact of them on the environment. In this way, the natural fibers have received considerable attention because of some their characteristics, besides low cost, they are flexible, viable, renewable and considered abundant substitutes. Thus, this paper is about curaua fibers, which belong to the family Bromeliaceae and it intends to compare the mechanical strength between epoxy composite reinforced with random short curaua fibers and aligned long curaua fibers. The results show that aligned long curaua has higher mechanical strength.

Comparative Analysis of Curaua Fiber Density Using the Geometric Characterization and Pycnometry Technique

One of today’s biggest concerns has been environmental issues, which has motivated researches and the development of materials from renewable resources and environmentally friendly. Natural fibers have excelled in replacing synthetic fibers used in composites manufacturing, because natural fibers are biodegradable, abundance in the nature, low cost, low density, high strength, among others. Due to these qualities, some natural fibers are used for many purposes in automobile industry. However, the natural fiber has irregularities and pores in its structure which directly impact the density determination by geometric techniques and, accordingly, the volume of fibers used in composites. Therefore, the main objective is this study is to determine the density of curaua fiber by pycnometry and to compare it with the commonly used geometric technique.

Izod Impact Test in Polyester Matrix Composites Reinforced with Blanket of the Malva and Jute Fibers

A natural fiber presents interfacial characteristics with polymeric matrices that favor a high impact energy absorption by the composite structure. The objective of this work was then to assess the Izod impact resistance of polymeric composites reinforced with one or two layers of batt malva and jute fibers. The results showed a remarkable increase in the notch toughness with increasing layers of mauve blankets and jute. This can be attributed to a preferential debonding of the fiber/matrix interface, which contributes to an elevated absorbed energy.

COMPARATIVE MECHANICAL ANALYSIS BETWEEN EPOXY COMPOSITE REINFORCED WITH CURAUA AND EPOXY COMPOSITE REINFORCED WITH FIBERGLASS

Natália de Oliveira Roque Maciel1 Carolina Gomes Dias Ribeiro2 Jordana Barreto Ferreira2 Janaina da Silva Vieira2 Frederico Muylaert Margem3 Carlos Mauríco Fontes Vieira4 Sérgio Neves Monteiro5 Resumo Atualmente uma das maiores preocupações da humanidade está relacionada as questões ambientais, o que tem motivado a pesquisa e o desenvolvimento de materiais provenientes de recursos renováveis e ambientalmente amigáveis. A despeito disso, este trabalho objetiva comparar a resistência de compósitos desenvolvidos com fibras naturais e, portanto, ambientalmente amigável e de compósitos desenvolvidos com fibras de vidro, que por sua vez apresentam impactos ambientais desde a fabricação até o descarte. Foram fabricados 13 corpos de provas para amostras contendo 0% de fibra, 30% de fibra de curauá e 30% de fibra de vidro na matriz epoxídica e ensaiado na máquina de tração. Os resultados obtidos apresentam valores bastante superiores para as amostras contendo fibras de vidro, contudo, ao relacionar a tensão do compósito com a respectiva densidade da fibra, foi possível constatar que os compósitos com fibras naturais chegam a apresentar resultados superiores aos compósitos fabricados com fibras de vidro. É possível concluir, portanto, que do ponto de vista da propriedade mecânica em questão é possível substituir as fibras de vidro por fibras de curauá. Palavras-chave: Compósito; Fibras naturais; Fibra de vidro; Propriedades mecânicas.

COMPARATIVE IZOD IMPACT TESTS OF EPOXY COMPOSITE REINFORCED WITH CURAUA FIBERS AND FIBERGLASS

Natália de Oliveira Roque Maciel1 Carolina Gomes Dias Ribeiro2 Jordana Barreto Ferreira2 Janaina da Silva Vieira2 Frederico Muylaert Margem3 Carlos Maurício Fontes Vieira4 Sérgio Neves Monteiro5 Resumo Nos últimos anos, especialmente fibras naturais extraídos de plantas lignocelulósico, ganharam atenção devido ao seu desempenho como engenharia de reforço compósito polímero. Por exemplo, as fibras lignocelulósicas extraídos a partir das folhas da planta curauá (Ananas acutifolius) exibir um potencial de reforço devido à sua relativamente alta resistência. As fibras, entre 0 a 30% em volume de, foram misturados com resina de poliéster sob pressão num molde metálico, e curada à temperatura ambiente durante 24 horas. Este trabalho procura avaliar a resistência ao impacto deste tipo de matriz de epóxi fibra de reforço. A resistência ao impacto aumentado substancialmente com a quantidade relativa de fibras de curauá reforço do compósito. Este desempenho foi associada com a resistência imposta pelas fibras e o comportamento de propagação da fissura Palavras-chave: Fibras de curaua; Ensaio de impacto izod; Matriz epoxy.

Tensile Strength Tests in Epoxy Composites with High Incorporation of Malva Fibers

The natural fiber extracted from the leaves of malva plant, Urena lobata L., are currently among the most studied natural fibers, mostly because of its mechanical performance associated with high tensile strength and flexural strength. It is known that with the increase of fibers volume fraction the composite significant increases its tensile strength. This was obtained with amounts up to 30% in volume of malva. Thus the present work aims to study the influence of higher volumes of fiber on the tensile strength of specimens prepared under 5 tons of pressure. The fibers were previously washed and dried in an oven at 60oC, after that poured together with the epoxy resin and catalyst mixture in the metal molds bone-shaped, and pressured to ensure specimens quality. The tensile strength increased significantly with higher amounts of malva fiber incorporated in the epoxy matrix. This better performance can be directly related to the fracture obstacle imposed by the fibers as well as the type of cracks resulting from the fiber/matrix interaction.