DESIGN AND ANALYSIS OF FOLDING PATTERNS OF MEMBRANE REFLECTORS

Abstract

Inflatable structures are ultralight membrane structures which can be deployed in very large volume in space compared to their stowed configuration while the launch of a satellite. The dissertation started with a question of Folding a thin membrane of space qualified material. These questions open up into three basic branches of possible areas that are realized in the work. First, the types of folding patterns that are possible for a membrane structure and selecting the most suitable one among them based on its efficiency to pack. Secondly, the deployment behavior of the folded membrane. This explores the question of what are the steps of the deployment. And possess the opportunity to re-iterate and include the condition of smooth deployment with that of packaging. Thirdly, the post-deployment analysis of the deployed membrane to study its behavior of under different conditions. The Origami, Japanese art of paper folding, is applied to fold the membrane. The four basic types of folds are identified initially – Z-fold or accordion fold, roll fold or wrapping, spiral fold and fan fold. In folding, the major challenge packaging is the creases. Unlike wrinkles, the creases are permanent non-linear discontinuities that appear at fold-lines. The major criteria for selecting the fold pattern is to minimizing crease. The crease is modeled as an anisotropic and empirical formula for young’s modulus is experimentally calculated. The numerical analysis on the creased membrane is done and realizing that it also effect wrinkling. The creased also removed to create a split. Its effect is studied on the performance. The pattern thus formed are known as hinged pattern and ligament pattern. For deployment of the membrane different types of mechanism have been studied. The deployment of planar structure can be centrifugal, linear or combination of both. The deployment in this thesis is designed as a two-step deployment process. Each diagonal ends are deployed in straight line in order. This gives steady deployment. A numerical simulation study is carried out for a post-deployed membrane structure. The results for the pristine membrane, Crease and split membrane type of patterns are compared to the different parameters and boundary conditions. Experimental setup is made to observe the linear two step deployment of the folded membrane.