Design of a Variable Camber Flap for Air Cargo Challenge Aircraft

• Autor(a) principal: Soares, Ricardo Manuel Vitorino
• Data de Publicação: 2020
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10400.6/11696
• topic: Casca de Asa Flexível; Dispositivo Flap; Perfil Asa Limpo; Domínio/Área Científica::Engenharia e Tecnologia::Engenharia Aeronáutica

The need for a more competitive Air cargo challenge (ACC) aircraft led the pursuit for a more aerodynamic efficient wing. This work details the various steps taken in the design of a gapless flap system with the actuation mechanism inside for a clean surface. Multiple flexible joint specimens designs were manufactured and tested with the help of a special constructed test bench to assert the required torque to bend certain degrees. The goal is to serve as a flexible skin in the flap hinge line. A system that rotates around an axis on the lower wing skin means that the upper skin changes in length, arising the need for a flexible material. A RTV silicone rubber was chosen to close the upper surface flap gap. A novel test apparatus was devised to determine the silicone Young’s Modulus and Poisson’s ratio so the sheet could be sized. An adhesion test was also performed using a suitable bonding agent to verify if it had the capability of performing the task at hand. The full range of hinge acting moments was determined. Aerodynamic hinge moment was simulated with XFOIL software, while the elastomer’s was calculated with the found properties and trigonometry. Due to the elastomeric nature of silicone, air pressure effects were evaluated using XFOIL Cp curves to calculate resulting loads and a subsequent FEM analyse with Ansys Mechanical module predicted the outer plane deformations. A program in Matlab was written to help dimension the actuation system. Optimization was achieved by comparing the servo motor available hinge torque with the resisting moments sum (aerodynamic, elastomer and flexible skin joint). With all the described methodology, a final design was purposed based on the central wing panel of ACC 2019 edition model. To not only validate the concept at hand but also the employed methodology, a small (250 mm span) section was manufactured using conventional 2 parts hollow moulded manufacturing process. For the novel concept, a silicone sheet bonding procedure was planned and required a special mould for the effect. After de­moulded, the section was trimmed and the servo motor was installed to check the concept functionality. A final experiment using a modified bench test was realized to compare the projected hinge moments with the built section one’s.