Technical Operations Support - I. Delivery Order 0033: Structural Monitoring With Piezoelectric Wafer Active Sensors

The use of piezoelectric wafer active sensor (PWAS) for structural health monitoring (SHM) has developed into a promising tool for real-time structural damage assessment. The 1-year research work described in this report addresses the following issues: (i) PWAS durability and survivability; (ii) optimum PWAS design; (iii) steering beam large-area coverage (embedded ultrasonic structural radar - EUSR); and (iv) probability of detection (POD) with PWAS probes (an initial investigation). The durability and survivability of the PWAS transducers has been confirmed under various environmental exposures for the duration covered in this one-year effort. These results give confidence in this new technology for installation on realistic structures. The report presents analytical methods and experimental results that can be successfully used in the design of active SHM systems. The EUSR steering beam PWAS phased-arrays method has been refined to increase it power of detection for various structural defects. It has been also proved that EUSR performance is not affected by typical structural curvature. The initial PWAS POD investigation has indicated that crack as small as 1.57 mm can be detected and imaged relatively easily. Overall, the results confirm that PWAS transducers are a technology with good potential for implementation in active SHM systems.