1. College of Materials Science and Technology, Nanjing University of Aeronautics and Astronautics, Nanjing, 210016, China; 2. College of Aerospace Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing, 210016, China.
Bees in the natural world have endowed the honeycomb with delicate tectonics. The honeycomb is made up of numerous hexagonal chambers of the same size. Ordered porous honeycomb structure is the best topological structure covering a two-dimensional plane. This kind of structure has excellent geometrical mechanical properties, so it is widely used in architecture field, material science, and aerospace, etc.
In this article, inspired by the ordered porous honeycomb structure, we designed a smart skin that was made of elastomer composite reinforced by honeycomb structure. We filled the honeycomb core with the polyurethane elastomer so the elastomer would be adhered to the cell walls of the honeycomb and the adhesion force would be increased significantly, eliminating the local deformations substantially. Finite element simulation was carried out and the fabrication process and sample test were carried out based on the simulation results. The smart skins were designed by stiffness tailoring, which led to the anisotropy of the structure and the geometry parameters. The anisotropic structure and the geometry parameters led to anisotropic equivalent modulus and bending stiffness of the skin, so that the skin could deform in one direction and resisted the aerodynamic load using high modulus and bending stiffness in the other direction. The deformable smart skin here might have potential application in morphing aircrafts.
Fig. 1 Honeycomb inspired macroscopic ordered porous structure in smart skin system.
At the microscopic level, we synthesized nanoscale ordered porous honeycomb-like carbon-silicon-metal (oxide) composite materials by using evaporation-induced self-assembly method. This kind of ordered porous material had highly ordered nanopore arrays, which could precisely control the ratio of each component to obtain the best impedance matching. The pore diameter distribution could be adjusted and the extremely high specific surface area and abundant pore structure might cause multiple scattering. These radar stealth materials had merits of wide absorption band, light weight, thin thickness, and excellent electromagnetic wave absorbing properties. They had potential application in radar stealth of weapon systems to improve the survival, penetration, especially in-depth-strike ability of the aircraft, missiles and other derived combat weapons.
Fig. 2 Honeycomb inspired microscopic ordered porous materials in radar absorbing.