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. This introduces a challenging stress state to the component. Specifically, high through-thickness interlaminar stresses can trigger delamination failure in the radii. The project is structured around three stages: a comparison of three geometric design iterations to identify the normalised stiffest design, the simulation of a physical test replicating real boundary conditions, and the manufacturing and testing of physical samples. In particular the manufacturing is carried out via vacuum assisted resin transfer moulding (VARTM), more commonly called vacuum infusion. Finite element analyses are carried out in ANSYS, with composite layups modelled using shell elements in Ansys using Ansys Composite PrepPost (ACP). Physical testing is carried out with an MTS tensile test machine and digital image correlation (DIC) is used to capture the experimental deformation of the tested samples. The results show that the simulation is able to capture the initial elastic response of the experimental tests with good agreement. The study aims to provide the building blocks to develop a novel T-joint design, with higher weight-normalised 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 to VARTM from the final production process intended by GKN Aerospace.