On the Transient Piezoresistive Response of Impacted Nanofiber-　Modified Epoxy

摘要

Nanofiller-modified composites have enormous potential for advanced structural health monitoring (SHM) because theyare self-sensing via their piezoresistive properties. However, the current state of the art is largely limited to static damagedetection between two distinct states (i.e. comparison between pre-damage and post-damaged states). This is animportant limitation because transient responses can provide great insight into damage events. It is therefore desirable toincorporate the transient effects into piezoresistive-based SHM. Unfortunately, the transient response of piezoresistivematerials has not been widely investigated. To address this limitation, this study examines the piezoresistive response ofa slender carbon nanofiber (CNF)-modified epoxy rod specimen due to impact loading as a function of time. Morespecifically, the change in voltage along the length of the rod is recorded as an idealized one-dimensional elastic planewave traverses through the specimen. This allows us to directly compare the rate of voltage change in the CNF/epoxy tothe speed of sound of the material. The fundamental insights into transient piezoresistivity herein uncovered has thepotential to greatly facilitate future advances in piezoresistive-based SHM.