Design of Novel Honeycomb Structures for Flexible Skin Using Reduced-Order Methods

In this work, an active deformable honeycomb structure is presented to achieve the flexible skin design of morphing wings. The driving displacement imposed along the in-plane direction of the skin can produce an out-of-plane bending deformation due to the completely opposite Poisson effect of positive and negative Poisson ratio honeycombs. First, the deformation mechanism of the positive and negative Poisson ratio honeycomb structure is studied. The relationship between the in-plane driving displacement and out-of-plane bending angle of a deformation unit is derived. Then, the reduced-order model with only one degree of freedom is constructed based on the third-order equilibrium equations and perturbation method. The nonlinear predictor solved by the reduced system is corrected when its numerical accuracy is not satisfactory for path-following analysis. Finally, the flexible skin of morphing wings is designed using the active deformable honeycomb structure to achieve the variable-thickness leading-edge and variable-camber trailing-edge demands. The reduced-order method is applied to conduct the large-deformation analysis of wing structures considering geometric nonlinearities. The numerical simulations validate that the honeycomb structure-based flexible skin approaches the target configuration precisely. The computational efficiency of the reduced-order method is much higher than that of the conventional method with the same simulation accuracy.