Optimal design of an airplane wing composite lattice panel under axial compression | Mekhanika | kompozitsionnykh | materialov i konstruktsii
> Volume 26 > №4 / 2021 / Pages: 490-500

Optimal design of an airplane wing composite lattice panel under axial compression

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Composite materials are now widely used in aircraft structures. However, the main structural concept for composite wing panels is a traditional stringer structure. Such structure consists of a load-bearing skin and reinforcing longitudinal ribs-stringers. Due to the special properties of polymer composites, this design usually does not reduce the composite panel’s weight compared to the metal prototype. An alternative to structures with a load-bearing skin is a composite lattice structure, where the main load-bearing elements are intersecting diagonal and transverse ribs. The ribs are formed from unidirectional CFRP, which has high specific strength and stiffness. Such a design scheme allows us to realize the high longitudinal properties of the composite material and to ensure a high weight efficiency of the structure. The paper is concerned with design of a flat rectangular panel consisting of a system of intersecting ribs made of unidirectional composite material by filament winding or lay-up processes. The panel is a structural element of an airplane wing. The panel is simply supported and compressed in the longitudinal direction. The relations which specify the optimal structural parameters of the lattice panel, i.e., the panel thickness, the ribs orientation angle, the ribs thickness and spacing are obtained. The optimal parameters provide the panel minimum mass under strength and buckling constraints. Optimization is undertaken by the method of minimization of the safety factors corresponding to possible modes of the panel failure. The method allows us to reduce the constrained optimization problem to the problem of conditional minimization. Two types of panels for which the length-to-width ratio is more or less then unity are considered. Optimization of a carbon-epoxy lattice panel is presented as an example.