Date of Award

Summer 8-1-2017

Level of Access Assigned by Author

Open-Access Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Civil Engineering

Advisor

William Davids

Second Committee Member

Andrew Goupee

Third Committee Member

Eric Landis

Additional Committee Members

Roberto Lopez-Anido

F. McNeil Cheatwood

Abstract

The hypersonic inflatable aerodynamic decelerator (HIAD) system under development by the National Aeronautics and Space Administration (NASA) has the potential to deliver the size of payloads to the Martian surface that will be necessary for future human-scale missions. An important step in realizing the promise of the HIAD system is to understand the structural behavior of this inflatable, textile, relatively compliant system. This is accomplished through structural testing and the development of structural modeling and analysis methodologies and tools. The structural modeling tools that have been developed to date utilize a continuum, shell-based finite element (FE) analysis approach. This methodology is capable of capturing the structural response of the HIAD system, but the models are time intensive to develop, difficult to parameterize and computationally intensive to run. In this dissertation a computationally efficient, beam-based FE modeling approach is developed. The beam-based modeling methodology addresses the challenges that are encountered in analyzing an inflatable, textile system, such as the effect of internal inflation pressure, nonlinear material response, the loss of pretension due to inflation pressure during loading, and the large deformations that occur as a result of having relatively compliant system. Material models are developed for use with both shell and beam-based FE models. A three-dimensional, corotational, flexibility-based, fiber beam modelling methodology is developed for the inflatable, braided members with axial reinforcing cords. The modeling methodology and tools are applied to the analysis of component level inflatable tubes and the single torus structures that make up the HIAD system. Initial validation of the modeling strategy is accomplished by comparing model predictions and parallel experiments conducted by others at the University of Maine. The modeling tools are then extended to analyze the full HIAD system, composed of multiple, stacked tori with straps. The interactions between tori are accounted for, along with the strap sets that connect tori to each other and to the center-body of the decelerator. The modeling methodology is then further validated by comparison with results from pressure tub testing of a full HIAD system conducted by NASA researchers. Following model development and validation, the analysis methodologies are used to investigate structural response of a full-scale HIAD devices. A number of configurations are investigated, including the influence of strap pretension and non-axisymmetric configurations and loading. The structural modeling tools are then coupled to optimization techniques to better understand the structural response drivers and demonstrate the feasibility of using the tools developed here in optimization studies.

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