Poisson's Ratio Adjustment of Deployable Antenna Reflector Material

As warp-knitted metal mesh of a deployable antenna reflector has negligible bending stiffness, when attached to curved boundaries under tension, a phenomenon called pillowing effect will deteriorate the surface accuracy of the reflector. This phenomenon can be derived from the momentless theory of thin shells. From the perspective of reflector materials, efforts to alleviate the pillowing effect has led to the emergence of Springback Reflector and Shell Membrane Antenna (Reflector). Both approaches have larger bending stiffness than metal mesh - no doubt this is favorable, the coming along large tensile modulus, however, make it impossible to tune the surface accuracy by tensioning the shell, as is popular adopted in mesh reflectors. The Springback Reflector and Shell Membrane Antenna must be cured on molds, this further strictly limited the physical size of the reflector. The concept of WEak STiffness COmposite Membrane (WESTCOM) aims to reduce the in plane tensile modulus, meanwhile sustaining sufficient bending stiffness to eliminate the pillowing effect. Bending stiffness is adjusted by tuning the thickness of the membrane, but this inherently increases the surface density of it. From the bending stiffness equation of thin plate, it becomes apparent when Poisson's ratio is approaching -1 the bending stiffness increases, while the in-plane modulus and the thickness of the plate remains small in quantity. Negative Poisson's ratio material is a rapidly developing metamaterial in recent years. If a reflector is made of membrane with negative Poisson's ratio, it may probably be another means to reduce pillowing effect. The deformed surface profile of a simply supported circular thin plate with negative Poisson's ratio, subjects to concentrated force acting at the center of the thin plate longitudinally is studied. Bending stiffness of the thin plate is tuned by varying the Poisson's ratio, the deformed surface profile is obtained by FEMA. The property of the deformed surface is evaluated by its Gaussian curvature. The final finding is a Poisson's ratio value that keeps the Gaussian curvature positive at every point on the deformed surface. An antenna reflector built by such kind of thin plate will be totally free of pillowing effect, and its surface profile be able to be optimized by applying discrete adjusting forces to it.