The Design and Finite Element Analysis of a Titanium Alloy, Structural Steel, and Grey Cast Iron Aircraft Fuselage Skin Panel

Abstract

The skin panel of the fuselage is one of the main parts of a transport plane's semi-monocoque airframe that bears the weight of the plane and must be as lightweight as possible while still withstanding cabin pressurization loads, inertia loads while in flight, and compressive loading caused by the plane bending without buckling. Using the same loading and support configuration, this paper compares the static structural and free-vibration (modal) response of three candidate metallic materials: structural steel, grey cast iron, and titanium alloy. The evaluation is based on finite element modeling of a representative fuselage skin panel. A distributed pressure load, which represents in-service aerodynamic and cabin loads, was applied to the panel's boundary and the geometry was created in CATIA V5. The analysis was conducted in ANSYS Workbench. Out of the three contenders, titanium alloy had the best dynamic performance and stiffnessto-weight ratio, with the lowest maximum total deformation (14.657 mm) and maximum equivalent elastic strain (6.83 × 10⁻³ mm/mm). It also had the highest natural frequencies across all six extracted modes. Grey cast iron had the most deformation (70.844 mm) and strain, making it the least suited for this application, while structural steel exhibited the greatest peak equivalent (von Mises) stress (1358.1 MPa) and the second-highest deformation (25.762 mm). Later on, the panel was subjected to an additional linear buckling test with Aluminium Alloy 7075 at a maximum cabin design pressure of 4000 kPa and an inertia load factor of 7 grams. The peak stress that resulted was 2.1696 MPa, which was well within the elastic limit of the material. The eigenvalue buckling solution verified a load-multiplier margin that was significantly higher than the design requirement. Aluminum Alloy 7075 was found to be structurally adequate against both pressurization stress and buckling instability for the load case under consideration, and titanium alloy was found to be the most suitable of the three metallic systems tested for stiffness-critical fuselage panel applications.