Stiffened panel structural optimization on wing skin of “WHALE” aircraft with local and global buckling criteria

Abstract

The purpose of this research is to obtain an optimum stiffened panel geometry on wing the skin of the amphibian aircraft “WHALE" with local and global buckling criteria. Local buckling prediction was done based on ESDU while global buckling prediction was based on empirical equation which utilizes radius of gyration of the structure, so that the calculation doesn’t require a high computational capability. Genetic Algorithm (GA) multi-objective optimization was performed to determine the optimum type of stiffener and the geometry of the stiffened panel which provides adequate buckling strength yet lightweight structure. A predetermined value of bending moment on the aircraft wing root was selected as a case study which result in a uniaxial compression load on the stiffened panel. The optimization results show that the more the number of stringers, the efficiency of a stiffened panel in resisting buckling will increase until a certain number of stringer. In the selected case study, integral J-stringer was the optimum type of stiffener with skin thickness of 2.45 mm, stiffener and flange thickness of 1.34 mm, stiffener height of 38.6 mm, stiffener pitch of 80 mm and 11.65 mm stiffener flange width. In comparison with the so called initial sizing method, this optimization shows a promising result of 27% weight reduction.