Optimization of Composite Aircraft Structures in Consideration of Postbuckling Behavior

Abstract

An approach is presented to determine the design that minimizes the weight in consideration of the postbuckling behavior of stiffened composite panels. Since, due to computational expense, for optimization purposes a nonlinear finite element approach is not appropriate, a semianalytical approach is implemented in the EADS MAS software LAGRANGE. A gradient-based optimization scheme is employed to determine the ply thicknesses and fiber orientation of the composite skins and the cross-sectional areas of the stiffeners. Strength and stability constraints are used. Based on two examples of different complexity, weight savings are shown to be due to the fact, that skin buckling is allowed above a certain load level.

Stiffness degradation of composite skin fields due to strength and buckling onset

“…1 The software enables the analysis and optimisation of large structures, such as fuselage barrels [30]. It was applied successfully within several civil and military projects (see Schuhmacher et al [41], Daoud and Calomfirescu [17] and Calomfirescu et al [14]). The incorporated linear finite element solver is similar to the commercial software MSC NASTRAN.…”

Imperfection sensitivity analysis of laminated folded plates

“…The design of composite structures is most often dominated by buckling [1,2]. For example, the demands for fuel efficiency are prompting the aircraft industry to revolutionize airframe construction to save weight, and thus fuel.…”