Mechanical Damping Properties of Carbon Nanofiber Reinforced Composites
AuthorVarischetti, Joshua Allen
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In this research an investigation of the damping enhancement achieved, utilizing carbon nano fibers (CNF) to epoxy resin is presented along with a corresponding model to predict damping performance. The addition of CNF fillers to the matrix allows for localized slip between the filler and the matrix on a nanoscale, wherein the matrix can de-bond from the CNFs, allowing the fillers to slip relative to the matrix; thereby, dissipating energy as frictional heat. Due to the nanoscale size of the filler, the specific surface area, of the CNF's, is very large when compared to traditional fiber reinforcement, this attribute allows small fractions of CNF fillers to have a large impact on the structural damping without any significant weight penalties. Moreover, once the composite returns to its undeformed configuration the interface between nano fillers and matrix will then re-establish the Van der Waals interactions that were broken to allow the slip. Thus, localized yet recoverable, frictional slip at the nano scale can be employed to significantly enhance strain dependent damping in composite structures wherein no permanent structural damage is evidenced. To better understand the damping response in CNF reinforced composites this study utilizes experimental and analytical approaches to develop modeling techniques that account for various fundamental attributes of high aspect ratio fillers, specifically the effect of filler aspect ratio, filler waviness, filler orientation relative to loading direction and the effect of multiple fillers on the damping performance and investigated in detail and corresponding modeling techniques are developed to address each of these factors in order to better predict the viscoelastic response of CNF reinforced composites. These models will be beneficial to address composite design while accounting for makeup, constituent properties, filler geometries, filler orientations, and their effective role in damping performance.