Theses and Dissertations

Issuing Body

Mississippi State University

Advisor

Lacy, Thomas E., Jr.

Committee Member

Kundu, Santanu

Committee Member

Koenig, Keith

Committee Member

Pittman, Charles U., Jr.

Date of Degree

12-14-2018

Original embargo terms

Visible to MSU only for 3 years

Document Type

Dissertation - Campus Access Only

Major

Aerospace Engineering

Degree Name

Doctor of Philosophy

College

James Worth Bagley College of Engineering

Department

Department of Aerospace Engineering

Abstract

Spacecraft are vulnerable to hypervelocity impacts (HVIs) from micrometeoroid/orbital debris (MMOD) while in space and must mitigate these using shielding. In this research aluminum honeycomb core sandwich panels filled with a shear thickening fluid (STF) were developed as a novel MMOD shielding concept. STFs display a marked rise in viscosity with increasing shear rate above a critical shear rate. The results of HVI experiments with impact velocities of ~4.8 km/s or ~6.8 km/s at 80oC or 21oC showed that incorporating a STF into shielding, as opposed to the STF’s liquid phase alone, can reduce damage to the core and the likelihood of back-side facesheet perforation in the event of HVI. STFs can be subjected to a significant temperature variation in many applications such as the HVI experiments in this research or when deployed on the surface of a spacecraft. The effect of temperature on the shear-thickening behavior was investigated using four low molecular weight polymeric glycols/fumed-silica suspensions. The dispersed phase volumeraction, its surface chemistry, and the chemical compositions of the suspending media were varied in a series of steady shear rheological characterizations over a range of temperatures. It was thought that hydroclustering mechanism initiated the onset of shear thickening, and this onset was shown to be more closely correlated to a critical shear rate rather than a critical shear stress. Evidence of the hydroclustering mechanism was sought using small angle neutron scattering (SANS) experiments. SANS steady state rheological characterization experiments were carried out on five low molecular weight polymeric glycols/fumed-silica STFs at the NIST Center for Neutron Research. The SANS experiments were conducted at shear rates below the critical shear rates, at the critical shear rates, and during shear thickening. In all the SANS experiments, the results showed an increase in scattering intensity with increasing shear rates indicating an evolution of the suspension microstructure consistent with the formation of hydroclusters.

URI

https://hdl.handle.net/11668/18742

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