The hexachiral prismatic wingbox concept

In this work the concept of using a chiral honeycomb as the internal structure for a passively morphing wing is explored. The use of a chiral honeycomb, which features an in-plane negative Poisson's ratio,potentially offers high deformability whilst maintaining structural integrity of the wing box. A finite element simulation was carried out, coupling a complete two-dimensional model of the wing and internal structure to a panel code flow solver. An iterative process was then used in order to predict the wing camber change with respect to air-flow. The concept was validated experimentally through the construction of a prototype wing for wind-tunnel testing. The measured response was non-linear with respect to aerodynamic loading, but the final deflected shape at the design case compared well with the finite element prediction. The concept was proven to work for small camber changes, with larger deflections predicted by tailoring the mechanical properties of the hexachiral core.