The piezoelectric ceramics is embedded in the glass fiber reinforced plastics (GFRP) laminate. A dielectric sensor is also embedded in the GFRP laminate as a reference sensor for the degree of cure. The cure monitoring of the FRP by the piezoelectric ceramics in autoclave processing is experimentally demonstrated. The impedances of the piezoelectric ceramics have strong temperature dependence. However, the impedances of the piezoelectric ceramics can be corrected to the temperature by the exponential function. Thus, the impedances of the piezoelectric ceramics at the non-resonance frequency are adopted as cure index of the GFRP laminate. The change of impedance at non-resonance frequency shows good correspondence with change of the log ion viscosity, which is measured by the dielectric sure monitoring sensor.
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