Abstract
Carbon nanotubes (CNTs) possess great potential for developing high-performance and multifunctional nanocomposites for a wide variety of applications. As the cost of producing CNT buckypaper, a thin film of CNT networks, continues to decrease while the quality increases, more users and companies are becoming interested in buckypaper for potential applications. Many of these applications, such as electromagnetic interference (EMI) shielding and fire retardant surface skins for fiber-reinforced composites or plastics, may not require buckypaper-based composites to be much stronger compared to fiber-reinforced composites. This means that there is a market for buckypaper even without its theoretical super strength, but desired functionality. There is however a number of challenges with the potential scale-up production of composite parts with affordable buckypaper materials usually made of low cost CNTs, such as multi-walled carbon nanotubes (MWNTs). Such buckypaper is usually very lightweight (10-25 g/m2), thin (10-20 microns), and fragile, hence even small variations and damage in the wet lay-up process can result in large quality variations in the final buckypaper composite. These variations include buckypaper volume fraction, resin rich areas, and contact between BP and other reinforcement materials etc. Thus, keeping the consistency of the resulting microstructure and quality of buckypaper composites is a very challenging issue. The objective of this project is to study nanostructure-permeability relationships of different types of buckypaper materials, and explore effective prepreg processes to make buckypaper composites with greatly increased consistency, quality, CNT weight fraction and uniformity in the resulting products. The experimental results show that buckypapers have very low permeability, about 8-12 orders lower than those of carbon fiber preform cases, and also sensitive to liquid polarity due to their nanoscale porosity and large surface area. Both solution and resin film transfer prepregging processes were studied to pre-impregnate buckypaper to achieve 50 wt. % CNT concentration. The late one showed better quality in the resultant nanocomposites, but difficult for high viscosity resins. Three case studies were also conducted to demonstrate quality and property consistency of buckypaper composites.
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