Mechanical Engineering ETDs

Publication Date

7-9-2009

Abstract

The effect of a moderate permanent magnetic field (i.e., 0.50 Tesla) on a structural epoxy has been investigated. The magnetic field induced-changes on the microstructure of the epoxy system where probed through wide-angle x-ray diffraction (WAXD) and texture analysis. Pole figures were generated for all the samples along the directions parallel and perpendicular to the applied magnetic field. This allowed, quantitatively, comparing the textures and fully understanding the mechanisms that result in a preferred orientation generation. The texture analysis revealed that under such moderate magnetic field and due to the diamagnetism of the epoxy system, the chains and the cross linking reorient biaxially in a plane that shares the magnetic field direction. The evolution of mechanical properties (modulus, hardness and toughness) under different thermo-mechanical environment was investigated using the instrumented nanoindentation. Improvements in both Youngs modulus and hardness by up to 6.6% were observed in the transverse direction of the magnetic field. However, evident by the measured elastic and plastic work under nanoindentation, it was observed that the magnetically annealed sample encountered slight embitterment. Furthermore, the current study reports enhancement on the mechanical properties of the epoxy when the nanoindentation tests are carried out under elevated temperatures (50-70 °C) below the glass transition temperature of the epoxy The time-dependent behavior of the epoxy was investigated under different thermal environments on light of the magnetic annealing- induced texture. The storage and loss moduli together with tan-delta as measures of the viscoelastic behavior of the polymer were measured using the continuous contact compliance module of the nanoindenter. The results of the current study showed that even under relatively low magnetic fields the mechanical properties, creep resistance and viscoelastic properties of the structural epoxy have been improved; tan-delta was measured to be 9.8% less for magnetically annealed compared to the neat epoxy sample.'

Keywords

Epoxy resins--Magnetic properties, Epoxy resins--Mechanical properties, Epoxy resins--Microstructure, Diamagnetism.

Degree Name

Mechanical Engineering

Level of Degree

Masters

Department Name

Mechanical Engineering

First Committee Member (Chair)

Leseman, Zayd

Second Committee Member

Luhrs, Claudia

Third Committee Member

Yu-Lin, Shen

Document Type

Thesis

Language

English

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