Mechanics and Applications of Pressure Adaptive Honeycomb

Abstract

A pressure-adaptive wing structure is presented that relies on the pressure-altitude relation to adapt the wing shape to the various flight conditions (e.g. landing and cruise). This structure employs conventional, certified aerospace materials and can be implemented in aircraft ranging from LSA to business jets and high-subsonic transports. The adaptive structure consists of a honeycomb which has cells that extent a significant length perpendicular to the plane of the hexagons. In each cell resides a pouch (bladder) that can be pressurized. Pressurization yields a change in the stiffness of the structure. In combination with a restoring force, this structure shows strains in excess of 50% without any plastic deformation in the honeycomb cell walls. Mass specific energy densities for this pressure adaptive honeycomb is on the par with shape memory alloy, which has the highest mass specific energy density of the adaptive materials. A mathematical model based on the equivalent properties of the pressurized honeycomb is developed and verified against experimental tests. The applicability of this new adaptive structure is proven in the wind tunnel for a pressure adaptive flap on a generic wing section resulting in an increase in maximum lift coefficient of 0.3.