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Nanofiller-modified composites have shown much potential for structural health monitoring (SHM) and nondestructive evaluation (NDE) because they exhibit self-sensing behavior via the piezoresistive-effect. To date, the piezoresistive effect has been used predominantly in isolation for cases of (quasi-)static loading. There is a comparative lack of work that investigates the piezoresistive-effect under mechanically dynamic conditions. This is important because combined piezoresistive-elastodynamic approaches could leverage the relationship between electrode geometry/topology and piezoresistive information carried in elastic waves. In other words, the question of how certain factors of electrode design, such as spacing between electrode pairs, impacts the measured piezoresistive signal has been little explored within the context of elastodynamics. Addressing this gap in the state of the art may yield insights into multiphysics approaches to SHM and NDE which seamlessly marry conductivity and vibration-based techniques. To this end, a simple prismatic carbon nanofiber (CNF)-modified epoxy rod was manufactured. Piezoresistive measurements were taken as a function of time by way of normalized resistance measurements between surface mounted electrodes. An electromagnetic shaker was employed to inject highly controlled one-dimensional stress waves into the CNF-modified epoxy rod. It was found that surface mounted piezoresistive measurements were able to accurately reconstruct the profile of propagating subsurface wave packets across the length of the rod. Transmission and propagation of the wave packets were extrinsically validated with the shaker force sensor and an external laser vibrometer (LV) system, respectively. Furthermore, artificial signal filtering was achieved by changing the distance between the electrode pairs. Lastly, the dispersion curves were constructed from piezoresistive measurements and extrinsically validated. Results from this preliminary investigation seeks to lay the foundational work for a new multiphysics SHM tool, piezoresistivity-coupled elastodynamics, that aims to provide an unparalleled level of understanding into material dynamic properties from direct electrical interrogation.
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