Numerical simulation of thin membranes with curved creases

Abstract

Deployable membranes are commonly used in the construction of solar sails, solar arrays, and sun shields. These structures are fabricated on the ground and then deployed to their operational configuration in space. These structures are very large in dimensions but need to be compacted into a very small package that can be stowed inside a launch vehicle. Membrane structures are often folded using different crease patterns and wrapped around a central hub to achieve the compacted state. The thickness of the membranes place and important role in selecting a folding pattern as one length of the membrane increases with layers overlapping around the hub. To get a smooth wrap, a viable option is to change the crease pattern geometry to a curved crease with changing curvature to accommodate increased thickness. Changing the geometry into a curved crease pattern needs to be analyzed properly to understand its suitability for use in deployable membrane structures. This study analyzes the effectiveness of curved and straight crease wrapping structures. Two numerical models are used for the analysis of each crease pattern to understand behavior. The curved crease wrapping pattern shows good overall wrapping motion with less stresses in the initial stages when compared to the straight crease wrapping pattern. The stress is reduced up to 26% in the initial stages. Also, a crease idealization technique is introduced in this study to incorporate the self-opening behavior of the membrane creases into the numerical model. This idealization technique is further evaluated for a multiple crease geometry with a Miura-Ori model. The crease modeling technique shows a good overall fit with the experimental results validating the numerical simulations.