Perpustakaan Digital ITB

Aircraft structures are required to maintain a high level of structural integrity to ensure flight safety. In fuselage structures, cyclic loading induced by cabin pressurization can initiate and propagate cracks. One of the most widely adopted repair techniques is the installation of a doubler plate using rivet joints. However, this repair configuration introduces additional stress concentrations around the rivet holes, which may promote crack propagation within the doubler. This study aims to investigate the propagation behavior of primary cracks in the skin and secondary cracks in the doubler based on the principles of damage tolerance. The analysis was conducted using the Finite Element Method (FEM) in Abaqus with the Contour Integral method, while analytical calculations were performed using AFGROW to determine the Mode I Stress Intensity Factor (SIF). Subsequently, the crack growth rate was predicted using the Paris law. The results indicate that the most critical location for primary crack propagation is the radial cut-out region of the fuselage skin. Crack propagation analysis shows that the crack in the cut-out fuselage skin reaches a critical crack length of 53.143 mm after approximately 3.33×105 loading cycles, whereas the crack initiating from the central rivet hole in the doubler reaches a critical crack length of 69.549 mm after approximately 5.96×105 loading cycles. These findings demonstrate that the installation of a doubler enhances the structural damage tolerance by extending the crack propagation life and providing a longer inspection interval before the crack reaches its critical length.