THE SCHOOL OF MATERIALS SCIENCE AND ENGINEERING
GEORGIA INSTITUTE OF TECHNOLOGY
Under the provisions of the regulations for the degree
DOCTOR OF PHILOSOPHY
on Friday, April 23, 2021
Blue Jeans Video Conferencing
will be held the
"Lightweight Approaches to Polyester Composites: Nanocellulose and Syntactic Foams"
Prof. Kyriaki Kalaitzidou, Advisor, ME
Prof. Robert Moon, MSE
Prof. Karl Jacob, MSE
Prof. Donggang Yao, MSE
Prof. Douglas Fox, American University, CHEM
The focus of this research was to understand the effect of filler characteristics and composite processing in polyester composites on properties with the goal of realizing lightweight, high strength composites. Composites were made at both lab scale via open mold casting, and pilot scale via compression molding of sheet molding compounds (SMC). The impetus for this study is a recent trend towards lightweighting in the automotive sector, primarily driven by new fuel efficiency standards. In this study three different directions are explored, the first one is to add a high-performance nanomaterial, cellulose nanocrystals (CNC), into the composite to enhance the properties without increasing density. The second is to add a low-density material, hollow glass spheres (HGS), to reduce the density without compromising the properties. The synergistic effect of adding both in the GF/PR is also investigated. The third is to laminate SMC in a functionally graded arrangement to reduce density without compromising surface properties. Although nanodispersion was not achieved, the surface modified CNCs displayed an enhanced storage modulus and improved elastic modulus, all without significantly increasing the composite density. Surface coating of HGS with CNC was successfully completed. CNC coated HGS-PR composites displayed enhanced storage modulus and reduced maximum water uptake relative to untreated HGS-PR composites. Functionally graded SMC was manufactured and showed good lamination and similar bulk properties to a monolithic formulation of similar density. This project has advanced our fundamental understanding of how modification of composite filler surfaces and composite structures can customize material density and mechanical properties.