Using Piezoelectric Ceramics, Nondestructive Testing Of Composite Materials

According to the piezoelectric effect of piezoelectric ceramic, two PZT patches were bonded on the surface of composites or were embedded in the composites. The PZT patches which as sensor and driver can be used in the real-time damage detection of composites.On the base of traditional spectrum analysis of signal recorded, the wavelet analysis was introduced and the program in Matlab language was made. With the wavelet packet decomposition of the signal, the relations between the change of response signals and damage characters were gotten. Based on the local stiffness of structure will change when there is a micro crack inside the structure and the quantum which reflect the local character of signal will abnormally break (the singularity of signal), analysing the singularity of signal with wavelet analysis, capturing the time of damage, monitoring the degree of damage and completing the system of online damage detection.