Aerospace Stiffened Panel Initial Sizing With Novel Skin Sub-Stiffening Features

Abstract

The introduction of skin sub-stiffening features has the potential to modify the local stability and fatigue crack growth performance of stiffened panels. Proposed herein is a method to enable initial static strength sizing of panels with such skin sub-stiffening features. The method uses bespoke skin buckling coefficients, automatically generated by Finite Element analysis, and thus limits the modification to the conventional aerospace panel initial sizing process. The approach is demonstrated herein and validated for prismatic sub-stiffening features. Moreover, examination of the generated buckling coefficient data illustrates the influence of skin sub-stiffening on buckling behaviour, with static strength increases typically corresponding to a reduction in the number of initial skin longitudinal buckle half-waves. IntroductionAn aircraft stiffened panel is a highly efficient structure, designed to carry a range of loading while maintaining a specified level of damage tolerance. One of the advantages of the stiffened panel design is in permitting sections to locally buckle at load levels below the ultimate required capacity of the structure, potentially enabling additional weight savings. This beneficial characteristic is due to the stable postbuckling response of stiffened panels. The efficiency of stiffened panel structure is influenced by the interaction of materials, geometric design and assembly processes. Such panel design grants greater potential for geometric design tailoring to the local panel structural requirements and the new manufacturing methods enable the geometric complexity at acceptable cost.

Wing Panel Design with Novel Skin-Buckling Containment Features

“…As detailed by Quinn et al [4], a tailored version of these analytical methods, adapted to facilitate skin BCF, can be used to analyse the initial buckling and ultimate failure performance of BCF panels. Table 2 presents the predicted initial skin buckling and ultimate failure loads of all specimens as analysed using these analytical methods.…”

“…The improvement in skin local stability is accomplished by designing the skin and additional skin features to initially buckle together as a combined unit between the typically larger primary longitudinal stiffeners and transverse rib or frame features. For these preceding studies, this modification of the skin local buckling behaviour is reflected by a reduction in the number of observed longitudinal buckle half-waves in the panel skin bays [1,4,18].…”

“…o improve the stability and reduce the mass of metallic stiffened panels local skin bay Buckling Containment Features (BCF) have been proposed and experimentally demonstrated for thin gauge fuselage applications [1][2][3][4]. The introduction of panel skin bay BCF can increase the out-of-plane bending stiffness at the skin bay centre, significantly increasing the local initial buckling resistance, and resulting in increased performance typically accompanied with a reduction in the number of initial longitudinal buckle half-waves.…”

“…Moreover the introduction of more design variables offers improved opportunity for local structural optimisation to local in-service loading [4]. This in turn will increase the potential to fully employ advances in manufacturing technology such as welding, extrusion, machining and additive layer manufacture, and new metallic material generations with improved stiffness, strength and durability properties.…”

“…Additionally, to enable utilisation and application on typical aerospace stiffened panel components, Quinn et al [4] also proposed a method to enable initial static strength sizing of panels with additional skin features. The developed methodology relies on Finite Element analysis to generate bespoke skin buckling coefficients for simply supported plates with various skin and skin feature geometric combinations.…”