Zero Poisson's ratio cellular structure for two-dimensional morphing applications

This work presents a novel zero Poisson's ratio (ZPR) honeycomb structure that can achieve deformations along two orthogonal directions and avoid the increase of effective stiffness in the morphing direction by the restraining the Poisson's effect in the non-morphing direction. Opposite to current ZPR honeycombs for one-dimensional wing morphing the proposed novel zero Poisson's ratio honeycomb configuration can perform two-dimensional deformation and present a cellular structure with smooth edges. Analytical models related to the uniaxial, in-plane shear and bounds of the out-of-plane (transverse) shear stiffnesses are derived and validated using the finite element techniques. The in-plane behavior of the honeycomb is investigated using a parametric analysis against the geometry of the unit cell, while the out-of-plane transverse stiffness is also evaluated vs. the gauge thickness of the cellular honeycomb structure panels. The theoretical and numerical models exhibit good agreement and show the potential of this novel ZPR configuration for morphing sandwich panel cores.