Aeroelastic Tailoring of a Representative Wing Box Using Tow-Steered Composites

There has been an increasing effort to improve aircraft performance through using composite tailored structures, not only to reduce weight, but to exploit beneficial aeroelastic couplings. Recent work has considered the ability to tow steer the composite plies to achieve better performance. Here, the potential wing weight savings of a full-size aeroelastically tailored wing are assessed by optimizing the properties of a three-dimensional finite element model using straight-fiber and tow-steered composites in the skins. One-and two-dimensional thickness and laminate rotation angle variations are considered as design freedoms. The jig shape is updated to maintain a fixed 1g flight shape, and optimization constraints are implemented on the strains and buckling loads due to maneuver and dynamic gust loads, flutter stability, and control effectiveness for different flight conditions. The optimal main fiber direction is rotated forward of the front spar direction in the outer wing, leading to extension-shear coupling in the skins, which increases the washout behavior of the wing. Washout effects shift the lift forces inboard and allow skin thickness reductions, but also lead to reductions in aileron control effectiveness. The optimized tow-steered laminate configurations achieved larger mass reductions than optimized straight-fiber configurations.