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Properties Of Rigid Foams For Application As Materials For Light Weight Structures In Space, Huichen Chi

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

The mechanical and mesoscopic structural properties of rigid cellular foam made of polystyrene have been investigated. Basic properties (e.g., density, total and available porosity, permeability, surface area, isotropicity, and cell size and cell wall thickness distributions) were measured. In most cases, alternative methods were used to determine which methods were most appropriate for the type of samples we studied. Standard compression and deflection mechanical tests were performed. The stress-strain curves and related mechanical properties were found to agree with standard cellular structural models of open-cell foams.

We investigated the effects of small (~ < 5 atm) hydrostatic stress applied to foam samples for long periods of time (~one day). We observed large changes (up to a factor of three) in the stress-strain diagrams, Young's modulus, elastic collapse stress, ultimate strength, resilience, Poisson's ratio, permeability, penetration depth, and available porosity. Effects were most pronounced above 2 atm applied pressure differential, but were observed even for 1 atm loads. Short-term exposure to loads up to ten times as large did not cause comparable changes. These changes were interpreted as resulting from observed changes in the mesoscopic structure occurring near the surface using standard cellular structural models.

This work was originally motivated by applications …

Probable Maximum Flood Estimation In Northern Utah, Khin Maung Win

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

The probable maximum flood (PMF) is used for the xxi assessment of maximum flood potentials in spillway sizing of new dams and in evaluating the adequacy of existing hydrologic structures. Determination of the PMF begins with the estimation of the probable maximum precipitation (PMP) for a particular dam site. Selecting hydrologic methods and assumptions for converting PMP to PMF, which are most appropriate for Utah conditions, is important to meet current inflow design flood (IDF) safety standards.

The objectives of this study were (a) to demonstrate a maximization approach to PMF determination, (b) to evaluate effects of basin characteristics and …