Minimum weight design of curvilinearly grid-stiffened variable-stiffness composite fuselage panels considering buckling and manufacturing constraints

Abstract

Abstract In this paper, optimum designs of a tow-steered composite fuselage skin stiffened by a grid of curvilinear composite stiffeners are obtained for minimum weight subject to buckling and manufacturing constraints. A simply supported cylindrically curved panel loaded by either uniaxial compression or combined uniaxial compression and shear is addressed. Using Python-Abaqus interface for modelling the panels and genetic algorithm implemented in MATLAB as an optimization platform, an integrated design framework is developed for obtaining the designs. The design variables include the number of stiffeners, the stiffener profile and the stiffener orientations as well as the fiber orientation angles of the variable-stiffness skin. Two different fiber paths with linear and circular arc variations are adopted to tailor the stiffeners and skin. For comparison with traditional grid-stiffened composite fuselage panels, minimum weight designs are also obtained for orthogrid and anglegrid stiffened quasi-isotropic skins. The goal is to identify the lightest weight of the three competitive designs. It is shown that the curvilinearly grid-stiffened variable-stiffness panel yields the most weight efficient design. Such a design provides for a weight reduction of up to 30% and 18% compared to orthogrid and anglegrid designs, respectively. As opposed to the stiffener trajectories, it is observed that the fiber trajectories of the skin have sharp curvatures. It is also observed that the shallow fuselage panels designed using the circular arc path satisfy the manufacturing constraints represented by the minimum turning radius of both the fiber and stiffener paths and have favourable buckling patterns to aircraft structures.