Date of Award

Summer 8-19-2016

Level of Access

Campus-Only Thesis

Degree Name

Doctor of Philosophy (PhD)

Department

Mechanical Engineering

Advisor

Vincent Caccese

Second Committee Member

Ali Abedi

Third Committee Member

Mohsen Shahinpoor

Additional Committee Members

Zhihe Jin

Lawrence Thompson

Abstract

The optimal design and efficient functionality of inflatable space structures requires extensive analysis, experimentation and modelling in order to predict responses in various environmentally challenging settings. The aim of this work was to develop an inexpensive and reliable assessment processes to model inflation, deflation and leak due to an impact or material porosity using advanced experimental, numerical and dimensional tools. The experiments focused on material strength, permeability, deflation and a three dimensional structural shape reconstruction. A series of monotonic and cyclic tensile and shear material tests on a thin polyurethane coated orthotropic fabric gave Young’s modulus, shear modulus, Poisson’s ratio and hysteresis in tension and shear. An experimental quasi-static inflation and deflation due to a single hole or passive porosity leak produced mass flow, temperature and pressure data sets for the semi-empirical formulation of the load, concentrated and porous leak coefficient curves for the numerical analysis of a deployable space inflatable. Structurally tailored three-dimensional shape reconstruction resulted in a pressure dependent sequence of composite areas and volumes for the development of the areal coefficients and for the geometric and volumetric comparison with the finite element analysis results. The inflation and deflation of a thin, one-segment, foldable and relatively large membrane space structure was examined by means of finite element analysis with the explicit and implicit schemes applied to control volume, corpuscular and arbitrary Lagrangian-Eulerian methods. The numerical solutions comparison was based on: mesh size, number of particles, leak and porous coefficients, fluid pressure - surface depth stiffness coupling, accuracy and computational efficiency. The corpuscular and arbitrary Lagrangian-Eulerian were found to be most resembling the experimental results in the dynamic shape changes and the time history of the gas properties, but computationally expensive. The control volume, although computationally efficient, was lacking the adequate fluid-structure interaction, thus accurately recreating the dynamics of the morphing surface. Only 0.2% to 1.75% and 1.5% to 3.25% difference was observed between the experimental and finite element inflation and deflation results respectively. An applied dimensional analysis was used with the inflatable model to obtain the expressions for an optimal pressure to prevent collapse, the leak coefficient and the porous leak coefficient for further exploration, analysis and possible utilization with other geometrically and material similar inflatable models.

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