Lightweight Approaches to Polyester Composites: Nanocellulose and Syntactic Foams
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The focus of this research was to understand the effect of filler characteristics and composite processing in polyester (PR) 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 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. HGS were also coated with CNC and then compounded to form CNC coated HGS-PR composites. The combined effect of adding both in GF-polyester resin 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 ion exchanged CNCs displayed an enhanced storage modulus and improved elastic modulus, while maintaining 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.