Hybrid piezoelectric/fiber-optic (HyPFO) sensor sheets are undergoing development. They are intended for use in nondestructive evaluation and long-term monitoring of the integrity of diverse structures, including aerospace, aeronautical, automotive, and large stationary ones. It is anticipated that the further development and subsequent commercialization of the HyPFO sensor systems will lead to economic benefits in the form of increased safety, reduction of life-cycle costs through real-time structural monitoring, increased structural reliability, reduction of maintenance costs, and increased readiness for service.
The concept of a HyPFO sensor sheet is a generalization of the concept of a SMART Layer™, which is a patented device that comprises a thin dielectric film containing an embedded network of distributed piezoelectric actuator/sensors. Such a device can be mounted on the surface of a metallic structure or embedded inside a composite material structure during fabrication of the structure. There is has been substantial interest in incorporating sensors other than piezoelectric ones into SMART Layer™ networks: in particular, because of the popularity of the use of fiber-optic sensors for monitoring the “health” of structures in recent years, it was decided to incorporate fiber-optic sensors, giving rise to the concept of HyPFO devices.
The development of HyPFO devices has included the development of novel techniques to incorporate fiber-optic sensors into SMART Layer™ devices, as well as the development of ancillary optoelectronic hardware and software. The advantages expected to be afforded by HyPFO sensor sheets include the following:
- It would not be necessary to install each fiber-optic or piezoelectric sensor individually on a structure. Sensors would be embedded in thin, flexible films that could easily be mounted on structures in minimal amounts of installation time.
- Because piezoelectric and fiber-optic transducers exploit different signal transmission mechanisms, interference between piezoelectric and fiber-optic transducers is expected to be minimal.
- Multiple measurements could be performed. For example, fiber-optic sensors could be used to measure temperatures, piezoelectric transducers could be used to measure concentrations of hydrogen, and sensors of both types could be used to monitor acoustic emissions.