Numerical modeling of single-layer electroactive polymer mirrors for space applications

Thin-film mirrors are attractive for large apertures, lightweight optical systems and microwave antennas operating in micro-gravity environments. The surface shape of these deployable thin film structures requires control to a precision range that depends on the specific applications. For optical systems, such surfaces need to be deployed and refined in the range of sub-microns. Electroactive polymers (EAP) are potential candidates for making such thin film materials. Generally, EAP materials are produced in thin film form with electrodes on their major surfaces. Depending on the reflectivity of the electrodes and surface roughness of the polymer they can also be produced with mirror finishes. The development of a controllable mirror made of single-layer EAP mirror was investigated and the results are described in this manuscript. The analytical solution for the required voltage/strain distribution to allow forming a parabolic mirror from a planar film is presented. Calculations show a single layer film made of currently available EAP has the capability to control the focal length of a 2-m diameter mirror from infinity to 1.25 m. The results are verified by FEM simulations. Keyword: Electroactive polymer, thin film mirror, thin film antenna, reflector, controllable membranes.