Buckling of metallic skin-stringer and sandwich panel structures: A comparative numerical study

In this study, global buckling behaviour of the metallic skin-stringer and honeycomb sandwich panels, which are used on the helicopter fuselage sections, is analysed. The metallic skin-stringer having different stringer cross sectional areas (z-, c-, and omega-section) and the metallic honeycomb sandwich panels in three variants (panels with longitudinal doublers, with transverse doublers, and without doublers) are examined with finite element simulations. The linear eigenvalue buckling analysis is used to calculate the critical global buckling load for simply supported boundary conditions. The most durable skin-stringer panel against the global buckling failure is determined to be the panel reinforced with the omega stringers. The panel with z stringers is found to be the least durable configuration against global buckling. The buckling strength of the panel with omega stringer is 13.1 and 15.6 percent higher than the panels with c and z stringers, respectively. The most durable honeycomb sandwich panel configuration against global buckling is determined to be the panel with transverse doublers. The panel without any doublers is found to be the least durable configuration against global buckling. The buckling strength of the panel with transverse doublers is 11.8 and 12.6 percent higher than the panels with longitudinal doublers and without any doublers, respectively. Honeycomb sandwich panels exhibit higher buckling strength compared to the skin-stringer panels. Critical buckling loads of the sandwich panels per kilogram are greater than those of the skin-stringer panels. Considering the structural, manufacturing, and environmental requirements, metallic honeycomb sandwich panels can be utilized as side panels of a helicopter fuselage and they can give better buckling performance per unit weight. Two panel concepts also can be used on different sections of a helicopter fuselage as long as they meet the structural requirements.