Self-sensing of pulsed laser ablation in carbon nanofiber-based smart composites

Laser-to-composite interactions are becoming increasingly common in diverse applications such as diagnostics, fabrication and machining, and directed energy weapon systems. These interactions can induce seemingly imperceptible damage to the material. It is therefore desirable to have a means of sensing laser exposure. Smart or self-sensing materials may be a powerful method of addressing this need. Herein, we present a study on the potential of using changes in the electrical properties of carbon nanofiber (CNF)-modified composites as a way of detecting laser exposure and degradation. To test laser sensing capabilities, CNF composite specimens were exposed to an infra-red laser operating at 1064 nm, 35 kHz, and pulse duration of 8 ns for a total of 20 s. The resistances of the specimens were then measured post-ablation, and it was found that for 1.0 wt.% CNFs, the average resistance increased by approximately 18% thereby demonstrating laser sensing capabilities. In order to expand on this result, electrical impedance tomography (EIT) was employed for spatial localization of laser exposures of 1, 3, 5, 10, and 20 s on a larger, plate-like specimens. EIT was not only successful in detecting and localizing exposures, but it could also find laser damages that were virtually imperceptible to the naked eye. Based on these results, this research could lead to the development of novel carbon-based smart material systems for real-time detection and tracking of laser exposure in the measurement, fabrication, and defense industries.