The Transient Response of Piezoresistive CNF-Modified Epoxy Rods to One-Dimensional Wave Packet Excitation

Abstract Introducing conductive nanofillers into polymeric, cementitious, and ceramic composites can impart multifunctional properties such as self-sensing capabilities via the piezoresistive effect. Much work has been done to utilize this multifunctionality for conductivity-based structural health monitoring (SHM) and condition monitoring. To date, the majority of such investigations concern static and quasi-static loading conditions. Much less work has been done with regard to general dynamic loading conditions such as transient wave propagation. This is an important gap in state of the art for two reasons: First, the self-sensing nature of these materials potentially allows for full-field (i.e. sub-surface) dynamics monitoring which cannot be achieved via traditional surface-mounted dynamic sensors. And second, conductivity-based and vibratory-based SHM are both independently well researched areas. Combined into a single, piezoresistive elastodynamic formulation, however, they may give rise to unprecedented new diagnostic capabilities. Therefore, the initial results presented in this manuscript seek to address this gap in the state of the art by experimentally exploring the role of dynamic excitation on transient piezoresistive behavior in nanocomposite structures. Specifically, an electromagnetic shaker is used to inject highly-controlled planar strain wave packets into a slender prismatic carbon nanofiber (CNF)-modified epoxy rod. Resistance measurements are then taken as the wave packets travel along the length of the rod. It was found that resistance changes taken from the rod are able to accurately reconstruct the injected strain wave and can be used to discern dynamic properties of CNF-modified epoxy. An external laser vibrometry (LV) system was used as extrinsic validation. Results from this preliminary investigation may lay the foundation for a new exciting field of fully coupled piezoresistive elastodynamics.