A Comparison of Metallic and Composite Aircraft Wings Using Aerostructural Design Optimization

In this paper we examine the design of metallic and composite aircraft wings in order to assess how the use of composites modifies the trade-off between structural weight and drag. In order to perform this assessment, we use a gradient-based aerostructural design optimization framework that combines a high-fidelity finite-element structural model that includes panel-level design variables with a medium fidelity aerodynamic panel method with profile and compressibility drag corrections. In order to examine the effect of the choice of the objective, we obtain a Pareto front of designs by minimizing a weighted combination of the mission fuel burn and take-off gross-weight of the aircraft over a multi-segment mission profile. The structural model includes both strength and buckling constraints and includes a detailed laminate parametrization that is used to obtain the optimal lamination stacking sequence and impose manufacturing requirements for composites including matrix-cracking and minimum ply-content constraints. We show that the composite wing designs are between 34% and 40% lighter than the equivalent metallic wings. Due to this large structural weight savings, the composite aircraft designs exhibit a fuel burn savings of between 5% and 8% and a take-off gross-weight savings of between 6% and 11%.