Engineering the Microstructure of Carbon Fiber-Reinforced Polymer Composites by Cellulose Nanocrystal–Carbon Nanomaterials

Abstract

Carbon fiber reinforced polymer (CFRP) composites suffer from weak interfacial and interlayer bonding, and lack of control on the microstructure formation that has resulted in properties lower than theoretical predictions. Despite the promises, integrating carbon nanotubes (CNTs) and graphene nanoplatelets (GNPs) into CFRPs is challenging because of the need for complicated lab-scale processes and toxic chemical grafting or dispersants that makes conventional means of processing less compatible with existing industrial procedures for large-scale applications. Engineering the CNTs/GNPs nanostructured carbon fiber (CF) fabric through conventionally adopted coating approaches can effectively integrate the nanostructures in CFRPs that allow them to boost their functionality and tailor the microstructure of composite components. Hence, the preparation of homogeneous and stable coating suspensions of CNTs/GNPs without damaging their intrinsic properties and efficiently transferring the nanomaterials on the CF surface is essential to enhance the structural performance of CFRPs. This dissertation explores the scalable fabrication of CNT/GNP integrated CFRPs by coating approach and tests their structural and multifunctional contribution to CFRPs’. Cellulose nanocrystals (CNCs) are used to create hybrid nanostructures with CNTs (CNC bonded CNT) and GNPs that enable stabilization of carbon nanomaterials in nontoxic media, e.g., water, and promote the scalability of the process. This work is composed of three main divisions: First, the atomic level interaction of CNC and CNT/GNP is investigated using both experimental (transmission/scanning electron microscopy (TEM/SEM), atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS)) accompanied with quantum-level calculations (density functional theory (DFT)). Second, CNC bonded CNT/GNPs hybrids are integrated into CFRPs by immersion coating, and their effect on mechanical properties e.g., interfacial and interlaminar performance are articulated. Third, the multifunctionality of the manufactured composites is controlled through engineered sub-micron droplets of CNCCNT/GNP to achieve the desired properties such as electrical and/or thermal properties along with mechanical strength. This dissertation presents new possibilities to precisely control the material microstructure and enables the engineering of the bottom-up manufacturing of hybrid nanostructured composites.