Sandwich for aeronautical applications

• Autor(a) principal: Sousa, Nuno Neves de
• Data de Publicação: 2018
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10400.6/8739
• topic: Electromecanical Behavior; Mechanical Behavior; Multifunctional Materials; Sandwiches; Self-Sensing Material.; Domínio/Área Científica::Engenharia e Tecnologia::Engenharia Aeronáutica

Carbon fiber laminates and sandwich structures are widely used due to their extraordinary mechanical performance (high specific strength, specific modulus, resistance to corrosion and resistance to fatigue), in the case of sandwiches, the high performance of the carbon laminates can be increased by the low density of the core. Besides that, carbon fiber is a conductive material, beyond its mechanical advantages, it has the potential to be used as a self-sensing material. This work aimed to analyze the use of sandwich composite structures in aircraft, to manufacture, and to study the mechanical and electrical properties of a sandwich composed of two carbon fiber faces and a structural foam core. The experimental work started with a study on the foam core, to access the impact of the adhesive curing temperature in the foam’s mechanical behavior. There was an increase on the ductility of the foam, but the flexural strength did not suffer significant changes. Posteriorly, three-point bending tests were carried out on carbon fiber laminates, with two different geometries, so compressive and tensile failures could be studied. The specimens that failed to compression showed a flexural strength of 1066.21±4.7% MPa, while the ones that failed under a flexural stress of 1238.49±7% MPa. The sandwich specimens with different adhesive bonds and geometries were tested and the short samples with reinforced bond failed to compression under a flexural stress of 100 MPa ± 5%, while the long samples showed several failure modes under a flexural stress of 86 MPa ± 7%. An electromechanical analysis was conducted to study the piezoresistive response of the sandwich skins. From this analysis was possible to show that there is indeed a relation between the electrical resistance and the applied strain.