A buckling solution and a non-linear post buckling solution were employed for the wrinkling analysis of a tensioned Kapton square membrane. The buckling solution with significantly reduced bending stiffness creates localized buckling modes accounting for the wrinkle formation in the membrane. The non-linear post buckling solution with an updated Lagrangian scheme describes the detailed wrinkle evolution during the loading process. Simulations show wrinkle amplitudes decrease as the tension load increases. The wrinkle number and distribution remain stable until loads exceed a certain level, then new wrinkles occur usually by splitting from existing wrinkles. The evolution of existing wrinkles and formation of new wrinkles in simulations are consistent with experimental observations.

The objective of this research was to predict the influence of non-uniform temperature distribution on solar sail topology and the effect of such topology variations on sail performance (thrust, torque). Specifically considered were the thermal effects due to onorbit attitude control maneuvers. Such maneuvers are expected to advance the sail to a position off-normal to the sun by as much as 35 degrees; a solar sail initially deformed by typical pre-tension and solar pressure loads may suffer significant thermally induced strains due to the non-uniform heating caused by these maneuvers. This on-orbit scenario was investigated through development of an automated analytical shape model that iterates many times between sail shape and sail temperature distribution before converging on a final coupled thermal structural affected sail topology. This model utilizes a validated geometrically non-linear finite element model and a thermal radiation subroutine. It was discovered that temperature gradients were deterministic for the off-normal solar angle cases as were thermally induced strains. Performance effects were found to be moderately significant but not as large as initially suspected. A roll torque was detected, and the sail center of pressure shifted by a distance that may influence on-orbit sail control stability. Nomenclature A = Flat-sail projected area for one quadrant, 75.6 m

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