Hybridization effect on mechanical properties of composite laminates

• Autor(a) principal: Monjon, Alice Marie Albina Michel
• Data de Publicação: 2022
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10400.6/13013
• topic: Fibra de Carbono; Fibra de Kevlar; Fibra de Vidro; Fluência; Hibridização; Propriedades de Flexão; Relaxamento de Tensão; Resistência ao Cisalhamento Interlaminar; Taxa de Deformação; Domínio/Área Científica::Engenharia e Tecnologia::Engenharia Aeronáutica

Composite materials are increasingly being used in the aeronautical industry. Although carbon fibers are the strongest and most used in the aeronautical sector, these fibers collapse quite suddenly due to their fragile nature leading to catastrophic damage. In order to minimize this effect, an alternative technique is used, which consists of combining these fibers with another less fragile type, such as Kevlar fiber, in order to obtain a material with a more ductile behavior. As the viscoelastic behavior is not much discussed in the available open literature, this work intends to study this mechanical property in several hybrid composites involving carbon, kevlar and glass fibers. For a better understanding of this phenomenon, the static behavior and tenacity of these materials were also studied. For this purpose, the effect of hybridization on flexural properties, interlaminar shear strength, creep and stress relaxation was studied in eighteen hybrid combinations combined with an epoxy matrix. It was observed that hybridization can create a more tenacious and balanced composite. The stacking sequence has a significant influence on the mechanical properties of laminates. As such, for all mechanical tests, carbon fibers are better in compression if hybridized with kevlar and better in tension if hybridized with glass. Glass fibers have always performed better under compression and kevlar fibers always perform better under tension, regardless of which other fiber they are hybridized to. With these positions in the laminate, the composites achieve greater tension and stiffness, but less deformation, greater interlaminar shear strength, less creep and less stress relaxation. As for the number of fiber layers, in the bending properties, a lower percentage of kevlar in the laminate results in higher bending stress and interlaminar shear strength. However, for the viscoelastic behavior of hybrid composites, the number of layers has no direct influence on the creep and stress relaxation values, since molecular rearrangements occur. In addition, a study of the bending properties for different strain rates in carbon fiber composites and fiberglass composites was carried out. In this way, it could be shown that there is a relationship between the strain rate and the flexural stress and stiffness of the composites. As the strain rate increases, there is an increase in bending stress and stiffness.