Curved large tape springs for an ultra-thin shell deployable reflector

This article presents a study of large tape springs to be used as ribs of an ultra-thin shell space deployable reflector. The tape spring, both longitudinally and transversely curved, is made of carbon/epoxy composite and subject to two-dimensional or three-dimensional folds. The behaviour of tape springs with different dimensional parameters during folding is investigated by finite element analyses and an analytical approach. Peak moments, steady-state moments and strain levels are obtained for several parameters such as curvatures, length, thickness, subtended angle, etc. The analytical approach considers the bending strain energy during two-dimensional folding of the tape spring, and it does not capture the full behaviour due to the assumptions made for the simple solution. The results obtained by the two methods are compared where they are applicable and are in agreement for the tape springs subject to two-dimensional folds. Feasibility of the curved large tape springs as a rib-reinforcing element for the deployable reflector with 6m diameter is investigated. A breadboard model of 90 cm diameter is manufactured and tested for packaging and deployment behaviour.