Structural Damping and Health Monitoring Enhancement via Multifunctional Carbon Nanotube-Based Composites Tailoring

Damping enhancement can lead to significant enhancement of mission capability in Army structures such as those used in rotorcraft, for instance. The objective of this investigation is to explore and understand the fundamental mechanisms of damping provided by carbon nanotubes (CNTs) in polymer-based materials such as those used to fabricate fiber composites, and to use this new understanding to explore further enhancements in damping. In addition, the feasibility of using carbon nanotubes for damage detection in polymeric composites is explored. Multi-scale micromechanics - molecular dynamics models of CNTs embedded in polymer resin have been developed to simulate damping of aligned and unaligned CNTs. The models point to the importance of CNT morphology and functionalization in tuning overall damping behavior. Novel methods of aligning and chaining carbon nanofibers and CNTs with AC electric fields have been developed and used to make epoxy-based nanocomposites. Multiphysics models of CNT chain formation in liquid epoxy explain the experimental observations of a peak growth rate at an optimal electrical frequency. A model of a polymer composite containing CNTs indicated that a crack could be detected with significantly greater sensitivity if external tuned resonance circuitry is used.
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