Deployment mechanics of highly compacted thin membrane structures

We studied the effects of membrane thickness and crease density on the forces required to unfold creased membrane structures. 26 cm-diameter models were made using two different thicknesses (7.5 μm and 25 μm) of polyimide film, and wrapped around a 4 cm-diameter hub using two different crease densities. They were deployed quasi-statically, and the deployment forces were measured. Two regimes were observed: an initial phase (up to about 85% deployed) of low and variable stiffness, and a second phase (above 85% deployed) of high stiffness. The thinner membrane models required higher deployment forces than the thicker membrane models during the initial phase.