Masters Theses

Date of Award

8-2009

Degree Type

Thesis

Degree Name

Master of Science

Major

Engineering Science

Major Professor

Dayakar Penumadu

Committee Members

Roberto S. Benson, John D. Landes

Abstract

A high resolution x-ray tomography system was used to study chopped fiber polymeric composites made of polypropylene resin, nickel coated carbon fiber and Eglass fiber. Procedures are developed to obtain micro-structured features of importance. In-situ tensile testing system was developed and integrated into the existing hardware for tomography equipment to study the evolution of damage and micro-structural features as a function of mechanical stress. High resolution x-ray tomographic images of glass fiber were collected and viewed on a micron scale. The radiographs were reconstructed to visualize the fiber content of the samples in three dimensional volume. In addition, glass fiber dogbone specimens were tested on a miniature tensile machine using x-ray tomography to view deformation of the samples in high resolution. Fractures in the chopped glass composite were observed for x-ray microscopy showing the dominant failure mechanism of the sample are low interfacial strength and adhesion between the fiber and matrix. Cracks were not observed until after failure by fiber pull-out using the digital microscopy method. Using SEM microscopy method, resin cracking and fiber debonding was observed for a carbon fiber with vinyl ester resin while under tensile loading. Important micro-structural information relationship with and mechanical behavior including variation modulus, yield and ultimate strength are discussed.

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