Analysis of Surface Deformation Due to Thermal Load on Circular Quasi-Isotropic Laminate Mirrors

One of the technology needs for large precision reflectors, for future astrophysical and optical communications satellites, is a material which can provide dimensionally stable lightweight characteristics in mechanical properties. Composite materials are being considered as next generation materials for space-borne application due to excellent mechanical properties such as high stiffness and strength to weight and low coefficient of thermal expansion. One of the critical problems in fabricating circular quasi-isotropic laminate mirrors is unacceptable surface finish (>λ/20) due to fiber print-through. To overcome such fiber print-through, additional surface coatings are commonly applied. In this paper, finite element analyses on circular quasi-isotropic laminated mirrors are performed to investigate thermally induced surface deformations. Numerical results show that surface deformations in ideal quasi-isotropic laminates exceed acceptable diffraction limit requirements in the presence of a thermal load, and additional resin rich layers applied on composite mirrors for fiber print-through mitigation create more critical surface deformations when thermal load is present.