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%.
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