Carbon nanotube coated piezoelectric ceramic for self-health-monitoring

The sensor signal of Lead Zirconate Titanate (PZT) piezoelectric sensors/actuator surface mounted to a structure with a thin adhesive layer is known to be influenced by the bondline quality and integrity. Monitoring the bondline health of sensor/actuators integrated into structures is becoming a major concern to guarantee the success and reliability of Structural Health Management systems. The design of a carbon-nanotube-coated PZT (CPZT) sensor was presented in earlier work shown that the bondline of CPZTs mounted on a structure, can be up to 274% stronger than that of conventional PZTs. A CPZT consists of a standard PZT surface coated with a high-density array of oriented CNTnanoelectrodes (CNTs-NEA). The CNTs-NEA in the interface plays the role of electrodes and of reinforcing filler material. This paper presents results indicating that CPZTs have better performance than conventional PZTs because CNTs in the interface can additionally allow monitoring the bondline integrity during manufacturing and in-service life of a structure. Tests were performed on CPZTs surface mounted on a metal structure with a thin nonconductive adhesive layer. CNTs in the interface were used to monitor adhesive curing by detecting electrical resistance variations of the interface due to phase changes in the adhesive during curing. Crack and debond formation in the interface were monitored in a similar approach.The CPZT is unique in that it is the only existing PZT that, not only has a stronger interface, but is also capable of self-monitoring the health of its bondline which is essential for accurate and reliable SHM systems.