Detection of Acoustic Emission Using Polyvinylidene Fluoride (PVDF) Film

- Attenuation of AE Wave in Wood and Wood-based Materials -

Polyvinylidene Fluoride (PVDF) film is the most sensitive among piezoelectric polymers, although it is less sensitive than PZT piezoelectric element used as ordinal AE transducer. PVDF film can be easily attached to curved and irregularly shaped materials, since it is thin (28 to 200µm in thickness) and quite flexible. The frequency response of PVDF film is flat, since it has a lower Q-value (sharpness of resonance), comparing with PZT piezoelectric element having a resonant frequency. The film has low acoustic impedance and matches with that of wood.
In this study, feasibility of PVDF film as AE sensor was investigated by comparing the attenuation of artificial AE wave generated by breaking of a pencil lead among several wood specimens and wood-based materials. It was clarified that PVDF film can be used as AE sensor for the non-destructive inspection of wood and wooden materials.

Table. 1. Comparison of some piezoelectric materials

Fig. 1. PVDF film and PZT piezoelectric transducer

Fig. 2. Example of the wave form of artificial AE detected by PVDF film

Fig. 3. Relation of AE amplitudes to distance using artificial AE source

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