A Disposable PVDF Sensor Applied for the Detection of Fatigue Crack Growth in Bonded Composite Joints

The application of polyvinylidene di-fluoride (PVDF) film as an acoustic emission (AE) sensor appears to be practical to detect the fatigue crack growth in composite materials and structures. A commercially available PVDF film sensor was employed to detect AE due to fatigue crack growth in the single-lap joints of graphite/epoxy laminates. Although the signal-to-noise ratio is not as high as those measured by PZT sensors, the result showed that the location of crack front could be predicted by the linear location of AE signals detected by the PVDF sensors. Since the composite materials usually produce very energetic AE signals, the extremely cost-effective form of PVDF sensors can be permanently mounted on composite structures for structural health monitoring as disposable ones. Piezoelectric polymer sensors are expected to be eventually embedded in composite structures provided the current limit of use temperature being increased by introducing co-polymerization with some heat resistant constituents.