Topology Design of Pressure Adaptive Honeycomb for a Morphing Fowler Flap

Abstract

A new method for designing a morphing Fowler flap based on pressure-adaptive honeycomb is detailed. Pressure adaptive honeycomb has been shown to be able to induce gross camber deformations in airfoil sections, such as a flap. However, due to the large amount of design variables the integration of the honeycomb as a distributed actuator in a flap structure has proven to be challenging. Therefore, a design tool is developed that can aid the designer in generating a honeycomb and flap topology that ensures two desired shapes under two distinct conditions: a cruise shape and a high-lift shape. This tool is based on a finite-element analysis of the pressure-adaptive honeycomb, where the honeycomb elements are reduced to simple rigid-bar elements connected by frictionless hinges. This tool is verified against analytical and experimental results. In the present implementation the honeycomb is attached to the upper skin of the flap, which itself introduces curvature in the aft flap section. An optimization algorithm calculates the exact thickness distribution of the skin that introduces the prescribed shape in high-lift conditions. By varying the pressure inside the honeycomb, the initial skin curvature distribution, or the honeycomb topology, the designer can evaluate how well the calculated shapes match the desired shapes in high-lift and cruise condition. This allows for a faster and more accurate topology designs that can ultimately enable an effective morphing solution to increase the maximum lift capability of Fowler flaps.