Optimization of Tapered Deployable Space Structures

Abstract

Modern spacecraft utilize deployable structures for many applications to strike a balance between functionality and size within a launch vehicle. Due to volume restrictions in a launch vehicle these deployable structures are stowed in a collapsed configuration during launch and deployed when the spacecraft successfully reaches a stable orbit. In this study, an optimization of a tapered composite beam deployable structure is performed to find an optimally performing design, minimizing wrapped strain energy and deployment dynamics. The beam will consist of a compressible, lenticular section that will include a taper ratio from the beam's root to its tip in a chord-wise manner. Material selection of the composite layup will also be included in the optimization with the ability to choose different composite mixtures, layup directions and ply thicknesses. Abaqus CAE, a commercial finite element analysis software, is used to conduct two analyses that make up the optimization architecture. The first analysis is to obtain the fundamental frequency of a beam design in its deployed state. The second will find stresses along the beam as it is wrapped examining the stored strain energy of the beam in the wrapped state. The second analysis will then continue to deploy the structure from its wrapped state and examine the rotational velocity and beam's oscillatory behavior during deployment. HEEDS MDO, a commercial optimization software, is utilized to conduct the optimization. Design variables will include beam dimensions and taper ratio, as well as material properties of the composite layup. The objective function will minimize the beam's weight, stored strained energy in the wrapped state and beam tip displacements during deployment. Constraints will be assigned on design variables, deployed system rotational velocity and transient stresses during wrapping will be checked for material failure using Hashin Damage Criterion. Finding a design that satisfies mission requirements and maintains structural integrity during wrapping and deployment will be challenging and computationally expensive. The optimization simulation presented in this paper aims to generate the best possible design that satisfies all requirements.