Composite flange design Conceive a novel flange design focused on stiffness

Abstract

Carbon fibre reinforced polymers (CFRPs) are increasingly adopted in civil aviation due to their exceptional stiffness-to-weight and strength-to-weight characteristics. Among the structural elements that benefit from CFRP construction, T-joints represent a critical component, commonly employed to transfer loads between structural members while maintaining overall assembly integrity. This thesis investigates T-joints acting as internal flanges subjected to axial loading, introducing an unconventional stress state that can trigger failure in the bend region, which is susceptible to interlaminar stress concentrations and delamination onset. The project is structured around three stages: a comparison of three geometric iterations to identify the normalized stiffest design, the simulation of a physical test replicating real boundary conditions, and the manufacturing and testing of physical samples via Vacuum Assisted Resin Transfer Molding (VARTM), more commonly called Vacuum Infusion. Finite element analyses were carried out in ANSYS, with composite layups modeled in ACP. Physical testing was carried out with a tensile test machine and digital image correlation (DIC) was used to capture the real deformation of the tested samples. The study aims to develop a novel T-joint design, with higher weight-normalized stiffness than the existing alternatives, after having validated the simulation framework against experimental results. Key limitations include the geometric simplification to a 100 mm representative section and the deviation of VARTM from the final production process intended by GKN Aerospace.