The employment of hydrogen has shown a lot of promises as an alternative for conventional fuel sources. However, if
not handled properly, hydrogen content as low as 4% can lead to a life-threatening catastrophe. Some sensors for
hydrogen detection have already been built to address this safety issue. Unlike most of the traditional hydrogen sensors,
the sensor developed in this study features high sensitivity, fast response, miniature size, and the ability to detect
hydrogen under room temperature. The sensor template has a special nanoporous structure, coming from self assembled
aluminum oxide after anodization process. Deposition of palladium particles into the nanopores brings superb hydrogen
sensing ability by introducing a granular structure of sensing particles. The sensor prototype has been tested under
controlled atmosphere with varying hydrogen concentrations.
Since the recognition of the advantages of using Lamb Waves in nondestructive testing (NDT), Lamb Waves and other guided waves have attracted more and more attention nowadays. Unlike waves used in conventional ultrasonic inspection, such as bulk longitudinal and shear waves, which propagate in the region of structure immediately around the transmitting transducer, Lamb Waves can propagate over a long distance. Previously in our work, monolithic interdigitated PVDF transducers for generating surface acoustic waves have been built by using photolithography technology. These sensors have been tested to be able to successfully excite and receive Lamb Waves. As an extension of previous work, this paper focuses on the implementation of interdigitated PVDF sensors on some laminated structures made of carbon fiber composite materials with flaws of different sizes. Experiments have been conducted, and results from PVDF IDTs have been compared with those from PZTs. Efforts have been spent on identifying the components of Lamb waves propagated in these sample structures and evaluating the differences in the received signals.
Piezoelectric materials have been widely used in ultrasonic nondestructive testing (NDT). PZT ceramics can be used to receive and generate surface acoustic waves. It is a common application to attach PZT transducers to the surface of structures for detecting cracks in nondestructive testing. However, not until recently have piezoelectric polymers attracted more and more attention to be the material for interdigitated (IDT) surface and guided-wave transducers. In this paper, an interdigitated gold-on-polyvinyldine fluoride (PVDF) transducer for actuating and sensing Lamb waves has been introduced. A specific etching technology is employed for making the surface electrodes into a certain finger pattern, the spacings of which yield different single mode responses of Lamb waves. Experiments have been performed on steel plates. Results from PVDF IDT sensors have been compared with those from PZT transducers for verification.
Polyvinylidene fluoride (PVDF) is a piezoelectric polymer material. One of its most attractive applications is being used as a sensor for structure monitoring. A suitable circuit interface plays an important role in sensor design. PVDF sensor can be used in a large variety of situations according to different design of circuit. The approach to a special circuit interface, which enables PVDF sensor to be utilized as a wireless “dynamic strain gage”, is presented in this paper. The wireless PVDF sensor was then tested and all the results have been compared with strain gage output for strain and displacement measurements.