ANALYSIS OF WRINKLE CONTROL STRATEGIES IN A CREASED MEMBRANE

Abstract

Thin membranes tend to wrinkle due to in-plane compressive stress induction whenever a tensile load acts on them. These wrinkles distort the surface smoothness of the thin-film planar membranes. When surface smoothness is a high priority, we cannot neglect these out-of-plane deformations. Space reflectors, solar sails, etc., are highly packed membrane structures that need the proper packaging & surface optimization techniques to minimize wrinkling. During the packaging, the formation of permanent creases magnifies the wrinkle amplitude and causes stress concentration near fold-lines. Therefore, specific control strategies need to be applied before deploying these membrane structures. Work in this report presents the implementation of wrinkle control strategies, including edge trimming to improve the overall surface flatness in a squareshaped planar membrane reflector. On the other hand, techniques like multi-material surface topology, pre-necking, and changing the number of anchor points have their limitations. This wrinkle control strategy helps in the suppression of wrinkles. Numerical analysis is performed using FE simulation software for non-creased and creased membrane reflectors of size 1 m × 1 m. Various cases have been investigated with multiple fold-lines and their orientations. It has been found that trimming the edges, suppresses the wrinkling effect, at a cost of material wastage. However, it is acceptable given the increase in highly efficient models. Promising results with minimum surface distortion are found for double creased models. Additionally, a higher number of fold lines are introduced to have a more compact packaging and it has been investigated numerically as well as experimentally. The outcomes of this dissertation work can be further extended for upscaled structures having different crease orientations.