Date of Award

Spring 2024

Access Type

Thesis - Open Access

Degree Name

Master of Science in Aerospace Engineering

Department

Aerospace Engineering

Committee Chair

Alberto Mello

First Committee Member

Alberto Mello

Second Committee Member

Sirish Namilae

Third Committee Member

Yizhou Jiang

College Dean

Jim Gregory

Abstract

As the use of composites continues to grow across aerospace, naval, automotive, construction, 3D printing, and other countless industries, so does the desire to continuously improve their mechanical properties. Improving the adherence of the fiber-matrix interface is one important step for amplifying the capabilities of composites. Work has been performed in modifying carbon fibers by growing zinc oxide (ZnO) nanorods in the fiber surface using a hydrothermal approach, increasing interfacial area and fiber-matrix friction. Macroscale evaluation has shown that the interfacial modification decreases the inter-ply movement and reduces the processing strains and residual stresses. To fully understand the mechanism taking place at the interface, a microscale evaluation was conducted to determine the fiber-matrix interaction, analyzing the thermal behavior and cure kinetics due to increase fiber surface area, and improved strength due to increase in interface friction. The proposed approach is to use HD DIC for mapping the interface by using speckles in nanoscale. The speckle pattern was created with Ti nano powder for strain maps in the fiber-matrix interface. The main objective of this research was to develop a protocol for speckling the modified single fiber composite and show that DIC can be used in microscopic level and to evaluate the fiber-matrix interface by means of nano indentation. A comparative analysis of DIC results from ZnO modified carbon fibers has shown that shear strains around the interfacial boundary are 60% reduced on average, as compared to neat carbon fibers, across all nano indentations from 8mN to 65mN of peak load. Results from this study prove that modification by ZnO growth on the surface of individual fibers has a significant benefit to the interfacial mechanical properties of fiber-matrix composites.

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