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Abstract(s)
A infusão por vácuo é um processo de fabrico realizado em molde fechado que pertence à família
dos processos de transferência de resina. Na infusão por vácuo, os reforços fibrosos são colocados
entre um molde rígido e um saco flexível, e é aplicado vácuo no interior do molde para gerar um
gradiente de pressão responsável por conduzir a resina para o interior do molde, impregnando
desta forma o reforço. Uma limitação presente neste processo é a baixa pressão de compactação a
ser exercida sobre o reforço, que não excede a pressão atmosférica, dificultando assim o fabrico de
peças com elevada fração volúmica de fibras. Um conhecimento mais aprofundado da compactação
do reforço é assim de extrema importância, uma vez que vai permitir projetar o processo de fabrico
tirando o máximo partido das limitações inerentes ao processo. Alguns estudos realizados nesta
área indicam que a imposição de ciclos de compactação ao reforço seco, antes da impregnação com
resina, aumenta a fração volúmica de fibras final da peça, tirando partido do comportamento de
histerese dos reforços fibrosos. No entanto, ainda há falta de conhecimento sobre o processo de
compactação de reforços fibrosos, pois ainda não foi proposto um procedimento detalhado para a
compactação do reforço antes da impregnação da resina através da infusão por vácuo. O objetivo
deste estudo é investigar o comportamento da compactação em reforços non crimp fabrics (NCF),
a fim de propor metodologias mais eficientes que promovam o aumento da fração volúmica de
fibras e, consequentemente, melhorem as propriedades mecânicas da peça em laminados feitos
através da infusão por vácuo, requisitos impostos pela indústria aeronáutica. Foram realizados
testes com diferentes curvas de pressão em função do tempo para descobrir qual seria o melhor
procedimento para aumentar a fração volúmica de fibras dos laminados. Concluiu-se que o número
de ciclos aplicados ao reforço, o tipo e o período da função escolhida têm uma influência
significativa nos resultados da fração volúmica de fibras.
Vacuum infusion is a closed-mold manufacturing process that belongs to the family of liquid composite molding. In vacuum infusion, fibrous reinforcements are placed between a rigid mold and a flexible bag, and vacuum is drawn inside the mold to generate a pressure gradient that will drive the resin into the mold, impregnating the reinforcement. One limitation of this process is the low compaction pressure that can be exerted on the reinforcement, which cannot exceed the atmospheric pressure, and thus hinders the manufacturing of parts with high fiber volume fraction. A deeper understanding of the reinforcement compaction is thus of extreme importance, because it will enable designing the manufacturing process taking full advantage of the limitations inherent to the process. Studies indicate that imposing cyclic compaction on the dry reinforcement prior to resin impregnation increases the final fiber volume fraction of the part, by taking advantage of the hysteretic behavior of fibrous reinforcements. However, there is still lack of knowledge regarding the compaction process of fibrous reinforcements, by which a detailed procedure for reinforcement compaction prior to impregnation in vacuum infusion is yet to be proposed. The aim of this this study is to investigate the compaction behavior of a non-crimp fabric (NCF), in order to propose more efficient methodologies that promote the increase of fiber volume fraction and, consequently, improve the mechanical properties of the part in vacuum infused laminates, which are requirements imposed by the aeronautical industry. Tests were carried out with different pressure curves as a function of time to find out which would be the best procedure to increase the fiber volume fraction of the laminates. It was concluded that the number of cycles imposed on the reinforcement, the type and the period of the chosen function have a significant influence on the fiber volume fraction results.
Vacuum infusion is a closed-mold manufacturing process that belongs to the family of liquid composite molding. In vacuum infusion, fibrous reinforcements are placed between a rigid mold and a flexible bag, and vacuum is drawn inside the mold to generate a pressure gradient that will drive the resin into the mold, impregnating the reinforcement. One limitation of this process is the low compaction pressure that can be exerted on the reinforcement, which cannot exceed the atmospheric pressure, and thus hinders the manufacturing of parts with high fiber volume fraction. A deeper understanding of the reinforcement compaction is thus of extreme importance, because it will enable designing the manufacturing process taking full advantage of the limitations inherent to the process. Studies indicate that imposing cyclic compaction on the dry reinforcement prior to resin impregnation increases the final fiber volume fraction of the part, by taking advantage of the hysteretic behavior of fibrous reinforcements. However, there is still lack of knowledge regarding the compaction process of fibrous reinforcements, by which a detailed procedure for reinforcement compaction prior to impregnation in vacuum infusion is yet to be proposed. The aim of this this study is to investigate the compaction behavior of a non-crimp fabric (NCF), in order to propose more efficient methodologies that promote the increase of fiber volume fraction and, consequently, improve the mechanical properties of the part in vacuum infused laminates, which are requirements imposed by the aeronautical industry. Tests were carried out with different pressure curves as a function of time to find out which would be the best procedure to increase the fiber volume fraction of the laminates. It was concluded that the number of cycles imposed on the reinforcement, the type and the period of the chosen function have a significant influence on the fiber volume fraction results.
Description
Keywords
Vacuum infusion fiber reinforcements atmospheric pressure compaction behavior fiber volume fraction