Thin-ply composite laminates capable of enduring high strains are currently under investigation for compliant deployable spacecraft structures. Deployable structures such as booms fabricated from these materials can be flattened and coiled to high curvatures, achieving a compact configuration for stowage. Once in orbit, they are released with minimal actuation for deployment, allowing the operational geometry to be recovered. Previous studies have shown that the viscoelastic properties of the composite epoxy matrix can negatively impact final shape accuracy due to stress relaxation during stowage. In addition, since the strain energy stored is relied upon for deployment, considerable relaxation can potentially result in deployment stall. Stress relaxation in composites and the aforementioned effects it can have on deployment have not been analyzed sufficiently for space applications. The objective of this thesis is to investigate the moment relaxation and curvature recovery behavior of thin-ply composite laminates through a combination of analytical, numerical, and experimental approaches. The viscoelastic Kirchhoff plate model that serves as the theoretical basis of the analyses is first presented. An analytical solution for the recovery of a composite plate after stowage is derived. The numerical integration of the viscoelastic plate constitutive equations and its implementation as a user-defined subroutine in finite element programs is then described. The subroutine allows relaxation of 3D thin-shell structures to be modeled, and is applied to simulate stowage and recovery of a thin-ply composite currently of interest for solar sailing applications. The subroutine is then compared with results obtained from experiments for a thin-ply composite for bending relaxation and curvature creep recovery after being unloaded.
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Master of Science in Aerospace Engineering (M.S.A.E.)
College of Engineering and Computer Science
Mechanical and Aerospace Engineering
Aerospace Engineering; Space System Design and Engineering
Length of Campus-only Access
Masters Thesis (Open Access)
Gomez-Delrio, Andrew, "Viscoelastic Analysis of High Strain Composites for Deployable Structures in Space Applications" (2020). Electronic Theses and Dissertations, 2020-. 220.