THE SCHOOL OF MATERIALS SCIENCE AND ENGINEERING
GEORGIA INSTITUTE OF TECHNOLOGY
Under the provisions of the regulations for the degree
DOCTOR OF PHILOSOPHY
on Thursday, April 22, 2021
BlueJeans Video Conferencing
will be held the
"Nanocellulose-based Glass Fiber Sizing for Lightweight Fiberglass Composites"
Prof. Kyriaki Kalaitzidou, Advisor, ME/MSE
Robert J. Moon, Ph.D., RBI
Prof. Karl Jacob, MSE
Prof. Paul Russo, MSE
Prof. Mark Losego, MSE
Development of our understanding of nanomaterial interfaces is crucial for the automotive industry, whose future will be shaped by lightweight materials and the economic and environmental benefits they yield. This work focuses on tailoring the interface between glass fibers and epoxy for the development of lighter, stronger fiberglass composites that may facilitate improved performance and fuel efficiency in automotive vehicles. The objective of this research is to investigate the ability of cellulose nanocrystals (CNCs) to enhance fiber-matrix interactions using lab-scale and scalable, industrially-relevant coating techniques. A thorough experimental approach integrated with molecular dynamics (MD) is employed to accomplish this objective. Coatings consisting of CNCs suspended in water and/or polymeric emulsions are developed and applied to the surface of glass fibers. The single fiber fragmentation test (SFFT) is used to assess interfacial shear strength (IFSS), a measurement of load transfer efficiency across the fiber-matrix interphase. IFSS is analyzed with respect to CNC functionality, CNC concentration, and dispersing medium used in the coating formulation, and these relationships are further studied based on the method used to apply the various coatings. Results indicate that CNCs can significantly strengthen the fiber-matrix interphase when these factors are optimized.
Further investigations are performed to understand the underlying phenomena responsible for this enhancement. This is accomplished experimentally through measurement of coating characteristics such as elemental composition and surface energy. Mechanisms of load transfer are further probed computationally. MD is used to model composite interfaces containing glass fibers, epoxy, and/or CNCs, and tensile load is applied to these models to assess stress-strain responses and fiber-matrix adhesion. These studies highlight processing-structure-property relationships, bridging the gap between formulation of coatings and their in-situ performance. This work offers a roadmap for the development of scalable CNC glass fiber coatings, with the goal of progressing coating technology toward large-scale production of light and strong fiberglass composites that are appealing to the automotive industry.