Carbon nanotubes (CNTs) easily form percolated networks when dispersed into polymers that can improve mechanical, electrical and thermal properties. Dispersing large mass fractions of high-aspect ratio CNTs into fiber-reinforced composites is much more challenging. The microscale fibers lead to CNT agglomeration that results in meager improvements to the interlaminar and bulk properties. This limitation can be overcome by directly grafting CNTs onto fiber surfaces before the resin infusion process. In the current study, this has been accomplished by functionalizing the CNTs using a hyperbranched polyethyleneimine (PEI) and then depositing them onto glass fiber surfaces under the influence of an electric field by a process known as electrophoretic deposition (EPD) [1]. The amine functionality enables the formation of primary bonds between the CNTs and the fiber/polymer surfaces, while providing a net-positive charge necessary for the EPD process. Hierarchical CNT-composites manufactured by direct fiber grafting display superior load transfer capabilities and show improvements in the electrical properties as compared to plain glass fiber composites. With potential application in aerospace industries, it is important to understand the effect of interfacial CNT networks on the polymer viscoelasticity in these materials. Multiscale characterization of viscoelastic properties and polymer dynamics was achieved by using both bulk (dynamic mechanical thermal analysis) and nanoscale (neutron scattering experimentation) measurements. Viscoelastic properties were measured by temperature-frequency scans, and the results were shifted across a broad range of relaxation times (10-5 s - 105 s) using time-temperature superposition principle [2], [3]. On the other hand, high-flux backscattering (HFBS) experiments were carried out to understand the mean square displacement of H atoms that are associated with the polymer relaxation dynamics at much smaller scales(
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