Ferroelectric Thin-Film Active Sensor Arrays for Structural Health Monitoring

Structural health monitoring (SHM) is an emerging field in which smart materials interrogate structural components to predict failure, expedite needed repairs, and thus increase the useful life of those components. Piezoelectric wafer active sensors (PWAS) have been previously adhesively-bonded to structures and demonstrate the ability to detect and locate cracking, corrosion, and disbonding through use of pitch-catch, pulse-echo, electro/mechanical impedance, and phased array technology. The present research considers structurally-integrated PWAS that can be fabricated directly to the structural substrate using thin-film nano technologies (e.g., pulsed-laser deposition, sputtering, chemical vapor deposition, etc.) Because these novel PWAS are made up of nano layers they are dubbed nano-PWAS. Nano-PWAS research consists of two parts, thin-film fabrication and nanoPWAS construction. The first part is how to fabricate the piezoelectric thin-film on structure materials. In our research, ferroelectric BaTiO3 (BTO) thin films were successfully deposited on structure material Ni and Ti by pulsed laser deposition under the optimal synthesis conditions. Microstructural studies revealed that the asgrown BTO thin films have the nanopillar structures and the good interface structures with no inter-diffusion or reaction. The dielectric and ferroelectric property measurements exhibit that the BTO films have a relatively large dielectric constant, a small dielectric loss, and an extremely large piezoelectric response with a symmetric hysteresis loop. The second part is nanoPWAS construction and how they are related to the active SHM interrogation methods. Nano-PWAS architecture achieved through thin-film deposition technology and its potential application for SHM were discussed here. The research objective is to develop the fabrication and optimum design of thin-film nanoPWAS for structural health monitoring applications.