Manufacturing process of nanotube/nanofiber nanocomposite: Dispersion and alignment study

Since carbon nanotubes (CNTs) were first discovered in 1990, many researchers have been striving to learn more about their remarkable mechanical and physical properties. With these exceptional properties, CNTs are considered by researchers as an ultimate reinforcement material for composite applications. However, many reports indicate that nanotube/epoxy composites are weaker or only slightly stronger than neat epoxy resins. This has been found to be primarily due to a combination of several factors, namely poor tube dispersion, inadequate alignment and weak interfacial bonding. In this study we focused on improving mechanical properties of nanocomposites and nanotube/carbon fiber multiscale reinforcement composites by improving nanotube dispersion and alignment.; In order to improve dispersion, it is necessary to quantify tube dispersion quality first. We proposed a quantitative method by using Differential Scanning Calorimeter (DSC) to quantify tube dispersion uniformity in tube/resin mixtures. The preliminary result shows that this method is able to characterize the dispersion quality numerically. The previous dispersion technique was also investigated and modified through the use of a Design of Experiment (DOE) to improve the tube dispersion quality in Epon 862 resin. Results indicate that the tensile modulus of 0.5wt% nanocomposites has 26.5% improvement over that of the neat resin. This improvement is four times higher than that of 0.5wt% nanocomposites made by the previous tube dispersion technique. This modified tube dispersion technique was also used to manufacture multiscale nanocomposites to enhance through-thickness properties. The results also demonstrate that with the addition of 0.12wt% single-walled nanotubes (SWNTs), the storage modulus, tensile modulus and tensile strength of multiscale nanocomposites have a 16.74%, 0.6% and 3.8% increase over that of conventional fiber-reinforced composites. In order to further improve the mechanical performance of nanocomposites and multiscale nanocomposites, studies were carried out to align nanotube and nanofiber in nanocomposites and multiscale nanocomposites using an 8.5T magnetic field. Even though a certain degree of tube alignment was observed by means of Raman spectroscopy, the obvious improvement of mechanical properties of aligned nanotube and nanofiber/resin nanocomposites was not obtained, due to low tube loading and high viscosity issues. However, the property improvement of aligned multiscale nanocomposites was observed. The short-beam shear (SBS) strength of 0.04wt% aligned SWNT multiscale nanocomposites showed a 13.05% increase over that of randomly oriented multiscale nanocomposites when the SWNTs were aligned along the through-thickness direction. The effect on the Tgs of nanocomposites when adding nanotubes was also investigated.