Development of Modeling Techniques for Damping Applications of Nano Structured Composites With High Aspect Ratio Fillers

Recent advances in the production and wide scale availability of nano scale constituents, coupled with ongoing fundamental research utilizing them as fillers in host matrices for a variety of specific engineering inquiries has led to a notable interest in the use of nano scale fillers for specific commercial applications, specifically in the aerospace industry. Damping is of particular importance in modern composites, having high stiffness and low density, damping becomes a large issue, both for structural integrity as well as noise attenuation. The largest obstacle which must first be overcome in order to incorporate the nano scale constituents in commercial applications is the development of design useful modeling and analysis techniques which allow for calculated design decisions based on constituent properties. Currently, there is a large gap in performance of nano structured composites, where in the current analysis techniques tend to overstate the performance achieved relative to experimental results. This discrepancy has been attributed to a number of factors ranging from non-perfect geometry, to issues at the interface between matrix and filler, however there has not yet been a detailed investigation to the ability to accurately predict composite viscoelastic performance based on constituent properties. On of the most common approaches to modeling high aspect ratio nano fillers, carbon nano tubes and carbon nano fibers, is to assume a perfect cylindrical geometry, even though it is well understood that these fillers can have a significant curvature or waviness to them. This investigation combines modeling work looking at the effect of the waviness and the resulting reinforcement provided, in terms of viscoelastic response, which is then compared to experimental results. Damping is characterized with respect to operating temperatures and frequency range, of specific interest is the low frequency range, which is traditionally more difficult to damp. Experimental investigations utilize dynamic mechanical analysis (DMA) to characterize viscoelastic performance, which is then compared to modeling data where it has been found that trends can be accurately predicted.