Design and analysis of inflatable space structures

  • Manpreet Singh Puri

Student thesis: Doctoral Thesis

Abstract

This thesis gives the conceptualization of inflation of inflatable membrane space structures. Although there has been little study using software simulation and the majority of documented research is based on theoretical numerical calculations. This research advanced the prior understanding of wrinkling within inflated membranes by using complex structures subjected to deformation loads. Within this thesis, a computational framework for the numerical analysis of the interaction between acting forces on the membrane and the membrane structure dynamics is presented. Moreover, in the case with thin membrane deformations, the synergy between the membrane wrinkling and structural forces has to be examined. This membrane structure-anatomical forces correlation results in a dynamic wrinkling problem, which can only be modelled easily and effectively by a simulation software that can integrate each assumption and attribute within the analysis. In the structural simulation within Abaqus FEA software, key consideration has to be given in modelling the geometric non-linearity behaviour of the membrane. By using the existing continuum expression for the virtual internal work in curvilinear coordinates. This is used to derive the modified fundamental formulation in which all subsequent analysis is established on and the initial equilibrium shape of the membrane. A critical feature of the new formulation is the prospect of adding pre-stressed forces to the membrane structure. The approach developed, established on an alteration of the material stiffness matrix to integrate the effects of wrinkling and deformation, can be utilized to calculate the behaviour of the membrane within a finite element simulation. In the wrinkling model, the state of the membrane element (taut, wrinkled or slack) is characterized by a mixed wrinkling criterion.Once it has been identified that the membrane element is wrinkled, an iterative scheme looks for the wrinkled orientation angle and the precise stress distribution, including only uni-axial tension in the wrinkle direction, is then derived. The wrinkling model has been verified and validated by contrasting the simulated conclusions with documented results for the instance of a time-independent isotropic membrane subjected to shear and axial loading. Utilizing the time integration method, a time-dependant pseudo-elastic stiffness matrix was represented and therefore, rather than calculating the convolution integral all through the Abaqus simulation, then we can calculate the behaviour of a membrane structure by superposition of a series of step by step increments in basic finite element software.The theoretical computations from the Abaqus/Explicit analysis were compared with documented results for the shear and axial loading. The results agreed very well, assuming friction and any relativistic dynamic effects were excluded. The discrepancy between the shear loading solution is 7% while the discrepancy between the axial loading is only 5% between the Abaqus modeland the documented model. This discrepancy could be the resultant of the source of energy dissipation from the visco-elastic behaviour during the loading and unloading of forces. It can be stated that for the Kapton HN membrane, this result falls within acceptable range but to increase accuracy, the load and unloading will be carried out on a set steady amplitude to inhibit in shock effects within the model.A three-dimensional finite element model which integrates wrinkling and frictionless contact has been developed to simulate the adaptive smart cell and cylindrical membrane structure. The loading of both structures is given by a non-uniform differential inflation pressure with a continual gradient adjacent to height. The resultant solutions are computed using Abaqus/Explicit software, with an integrated user-defined material subroutine to account for
Date of Award1 Jul 2014
LanguageEnglish
Awarding Institution
  • University Of Strathclyde
SponsorsUniversity of Strathclyde & EPSRC (Engineering and Physical Sciences Research Council)
SupervisorMalcolm Macdonald (Supervisor) & (Supervisor)

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