Optimized Designs of Composite Booms with Tape Spring Hinges

This paper presents an optimization study of a lightweight hinge consisting of a thin walled tube made of carbon fiber reinforced plastic with two longitudinal slots. The slot geometry is parameterized in terms of slot length, width and end circle diameter. Previously developed numerical simulation techniques to analyze the folding and deployment of this kind of hinges are used to carry out a series of parametric studies. The maximum strains are estimated by using the mid-surface strain and curvature obtained from a macro model of the structure to a micro model and averaging the strains over a half a tow width in the micro model. A maximum strain failure criterion is used for failure analysis. The optimization study is focused on finding a hinge design that can be folded 180 deg with the shortest possible slot length. Simulations show that the maximum strains can be significantly reduced by allowing the end-cross sections to deform freely. Based on simulations a failure critical model and a failure safe model were selected and experimentally validated. The optimized design is six times stiffer in torsion, twice stiffer axially and stores two and a half times more strain energy than the previously considered design.