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Abstract(s)
Os materiais compósitos de matriz polimérica estão cada vez mais presentes na engenharia devido
à sua alta resistência específica, combinando boa resistência mecânica com baixo peso. Estas
propriedades permitem o seu uso em várias áreas como a medicina, desporto, aeroespacial, defesa
militar e indústria automóvel.
Embora a produção de peças em materiais compósitos seja vantajosa, a sua montagem em
conjuntos exige, frequentemente, operações de maquinagem, tais como a furação. Durante o
processo de furação, é comum que os materiais compósitos sofram danos que afetam
negativamente as suas propriedades mecânicas e a confiabilidade geral do produto. Estes danos
podem estar relacionados com diversos fatores, tais como, a velocidade de avanço, velocidade de
rotação da broca e geometria da broca, sendo um dos mais frequentes a delaminação.
Esta investigação visa aferir a extensão da área danificada pela furação em laminados de resina de
epóxido e fibra de carbono (material de matriz polimérica) e determinar a sua influência na
resistência mecânica final.
Para tal, foi realizado um estudo utilizando 32 provetes de carbono/epóxido, nos quais foram
efetuados furos. Foram realizados segundo 8 hipóteses experimentais, com duas velocidades de
avanço e rotação distintas e brocas com 2 tipos de geometria diferente. Para determinar as
propriedades iniciais do material foram fabricados 11 provetes: 4 com as fibras orientadas a 0°; 4
com as fibras orientadas a 90°; e a 3 cross-ply. Após realizada a furação, a área de dano foi calculada
através das imagens resultantes da radiografia com líquido contrastante. Por fim, foram efetuados
os ensaios destrutivos (Pin Bearing e Bearing) de modo a avaliar a resistência mecânica de cada
uma das hipóteses e associá-las com a área de dano.
Após a análise dos resultados verificou-se que uma maior área de dano nem sempre representa
uma diminuição direta da resistência mecânica final do material.
Um aumento na velocidade de avanço resultará em uma área de dano maior.
Das configurações usadas, a broca de geometria brad associada a uma velocidade de rotação de
1500 RPM e uma velocidade de avanço 0,1 mm/rev, é a escolha mais acertada para a obtenção do
melhor acabamento e resistência bearing final.
Composite materials with a polymer matrix are increasingly present in engineering due to their high specific strength, combining good mechanical strength with low weight. These properties allow their use in various areas such as medicine, sports, aerospace, defense, and the automotive industry. Although the production of composite material components is advantageous, their assembly into assemblies often requires machining operations such as drilling. During the drilling process, it is common for composite materials to suffer damage that negatively affects their mechanical properties and overall product reliability. These damages can be related to various factors such as feed rate, drill rotation speed, and drill geometry. One of the most well-known and frequent damages is delamination. This study aims to assess the extent of the damaged area caused by drilling in epoxy resin and carbon fiber laminates (polymer matrix material) and determine its influence on the final mechanical strength. This monograph will publish the study conducted on 32 carbon/epoxy specimens. In these specimens, the holes were made according to 8 hypotheses, with two different feed and rotation speeds, as well as 2 distinct drill geometries. Additionally, 11 specimens were fabricated to determine the initial properties of the material (4 with fibers oriented at 0°, 4 with fibers oriented at 90°, and 3 cross-ply). After drilling, the damage area was calculated using the images that resulted from X-ray examination with a contrasting liquid. Finally, destructive tests (Pin Bearing and Bearing) were performed to evaluate the mechanical strength of each hypothesis and associate them with the damage area. After analyzing the results, was observed that a larger damage area does not always directly correlate with a decrease in the final mechanical strength of the material. An increase in the feed rate leads to a larger damage area. Among the tested configurations, the brad drill with a rotation speed of 1500 RPM and a feed rate of 0.1 mm/rev is the most suitable choice for achieving the best finishing and final bearing strength.
Composite materials with a polymer matrix are increasingly present in engineering due to their high specific strength, combining good mechanical strength with low weight. These properties allow their use in various areas such as medicine, sports, aerospace, defense, and the automotive industry. Although the production of composite material components is advantageous, their assembly into assemblies often requires machining operations such as drilling. During the drilling process, it is common for composite materials to suffer damage that negatively affects their mechanical properties and overall product reliability. These damages can be related to various factors such as feed rate, drill rotation speed, and drill geometry. One of the most well-known and frequent damages is delamination. This study aims to assess the extent of the damaged area caused by drilling in epoxy resin and carbon fiber laminates (polymer matrix material) and determine its influence on the final mechanical strength. This monograph will publish the study conducted on 32 carbon/epoxy specimens. In these specimens, the holes were made according to 8 hypotheses, with two different feed and rotation speeds, as well as 2 distinct drill geometries. Additionally, 11 specimens were fabricated to determine the initial properties of the material (4 with fibers oriented at 0°, 4 with fibers oriented at 90°, and 3 cross-ply). After drilling, the damage area was calculated using the images that resulted from X-ray examination with a contrasting liquid. Finally, destructive tests (Pin Bearing and Bearing) were performed to evaluate the mechanical strength of each hypothesis and associate them with the damage area. After analyzing the results, was observed that a larger damage area does not always directly correlate with a decrease in the final mechanical strength of the material. An increase in the feed rate leads to a larger damage area. Among the tested configurations, the brad drill with a rotation speed of 1500 RPM and a feed rate of 0.1 mm/rev is the most suitable choice for achieving the best finishing and final bearing strength.
Description
Keywords
Drilling Carbon fiber reinforced laminate Delamination Radiography Pin-Bearing test Bearing test