Efeito Da Incorporação De Fibras De Coco No Comportamento Dinâmico-Mecânico De Compósitos Com Matriz Poliéster

Abstract

ResumoRealizou-se um estudo da variação com a temperatura dos parâmetros dinâmico-mecânicos de compósitos com matriz poliéster incorporada com fibras de coco. Diferentes percentagens em peso de fibras de coco, até 40%, foram misturadas com resina poliéster ortoftálica e, após prensagem, curada por 24 horas à temperatura ambiente. Ensaios dinâmico-mecânicos (DMA) foram realizados para se obter os módulos de armazenamento e perda, bem como a tangente delta para cada tipo de compósito com diferentes quantidades de fibra de coco. Os resultados desses parâmetros revelam que a incorporação de fibra de coco diminui a rigidez viscoelástica do compósito com matriz poliéster. Esta redução na rigidez está associada à baixa tensão interfacial, o que dificulta a transferência de esforços mecânicos da matriz para a fibra. Ocorrem também modificações na temperatura de transição vítrea e no pico α de relaxação com a incorporação de fibras de coco. Em particular, o amortecimento do compósito que está relacionado ao valor da tangente delta, diminui a quantidade de fibra incorporada pelo fato de somente parte da tensão aplicada deformar a interface fibra/matriz. Palavras-chave: Fibra vegetal; Compósitos; Matriz poliéster; Comportamento; Temperatura de transição. EFFECT OF COIR FIBER INCORPORATION IN DYNAMIC MECHANIC BEHAVIOR OF POLYESTER-MATRIX COMPOSITES AbstractA study on the temperature variation of the dynamic-mechanical parameters of polyester matrix composites incorporated with continuous coir fibers was carried out. Different weight percentages, up to 40 wt.% of coir fibers, were mixed with orthophtalic polyester resin and, after press-molding, cured for 24 hours at room temperature. Dynamicmechanical, DMA, tests were conducted to obtain the storage modulus and the loss modulus as well as the tangent delta for each type of composite with different amounts of coir fibers. The DMA results revealed that the incorporation of coir fiber decreases the viscoelastic stiffness of the composite with polyester matrix. This reduction in stiffness is associated with a low interfacial shear stress, which makes it difficult for the mechanical load transfer from the matrix to the fiber. Modifications in the glass transition temperature and in the α relaxation peak also occurred with the amount of incorporated coir fiber. In particular, the damping response of the composite, associated with the value of the tangent delta, decreases with the amount of incorporated fiber owing to the fact that only part of the applied stress was used to deform the fiber/matrix interface.

Vibrational analysis of coconut fiber-PP composites

“…The loss factor is associated to the damping characteristic of the material, and the balance between elastic and viscous phase. Performing average and standard deviation calculations in the loss factor results, it is noticed that these values are 5.4±0.4%, same values observed for polyester/coconut composites 19 at room temperature. Monteiro et al 19 also observed this effect and the authors associated this behavior to the fact that the coconut fiber supports partially the stress and some deformation of fiber/matrix interface.…”

“…Performing average and standard deviation calculations in the loss factor results, it is noticed that these values are 5.4±0.4%, same values observed for polyester/coconut composites 19 at room temperature. Monteiro et al 19 also observed this effect and the authors associated this behavior to the fact that the coconut fiber supports partially the stress and some deformation of fiber/matrix interface. In this way, the energy loss is related to the interaction between the matrix and the fibers, or, in other words, if the interface is more resistant, the energy dissipation is reduced.…”

“…Furthermore, it's noticed that E and E ss values of pure PP are higher than those for PP/coconut composite. This behavior was also observed in Polyester/coconut composites 19 , associated to low interfacial strength between matrix and fiber, reducing the stress transference from the matrix to the fibers. This behavior is not observed in PP/ glass fiber composites 20 due to high adhesion that leads to low slip between matrix and fibers.…”

Synthesis and characterization of LDHs/PMMA nanocomposites: Effect of two different intercalated anions on the mechanical and thermal properties

“…Glass transition temperature was identified through tan δ peak in tan δ versus temperature curve. The E ′ value is directly related to the ability of the material to tolerate mechanical loads with recoverable strain and it is similar to flexural modulus 22. Conceptually, inorganic organic composites are often expected to become stiff and more brittle upon incorporation of inorganic fillers 11.…”

Análise Dinâmico-Mecânica Em Compósitos De Matriz De Polietileno Reforçados Com Tecido De Juta

“…(8) A técnica de DMA permite não somente avaliar o comportamento viscoelástico como também determinar a região de transição vítrea de compósitos poliméricos. (9) O ensaio de DMA também fornece informações sobre o módulo elástico ou de armazenamento (E'), o módulo de dissipação viscosa ou módulo de perda (E'') e sobre o amortecimento mecânico ou atrito interno tan δ ) ' ' ' (tan E E = δ de um material quando sujeito a uma solicitação dinâmica. (8) Esses parâmetros indicam o nível de interação dinâmica entre a matriz polimérica e a fibra que foi incorporada.…”