Bistable Deployable Composite Booms with Parabolic Cross Sections

The stable extended and coiled states of thin-shelled composite booms with parabolic cross sections are investigated in this paper. These conic shapes potentially offer greater stiffness properties when compared to circular cross sections, which is critical for improving the load-bearing performance of deployed booms. Inducing bistability through composite layups in parabolic booms would allow for controllable self-deployment due to a less energetic coiled state when compared to monostable booms. An inextensional analytical model is used to predict the stable coiled diameters of tape spring and collapsible tubular mast (CTM) booms with parabolic cross sections. The parabolic section is discretized into circular segments using biarc spline interpolation, which allows them to be integrated into the strain energy minimization procedure used to obtain the equilibrium states. When the parabolic booms are parametrically compared against circular booms with identical layups, flattened height, and mass, the former are found to generally have better stiffness performance while being less efficient in stowed volume, as evidenced by larger coiled diameters. Analytical coiled diameters and their strain energy are verified with finite element simulations for an optimal parabolic tape spring and CTM booms. Additional validation of the parabolic tape spring’s coiled diameter is provided by experimental measurements of boom specimens.