Composite materials evaluation by the wavelet transform and fuzzy pattern recognition

This paper studies the evaluation of bonding quality for thin composite plate. The main methods are wavelet transform and fuzzy pattern recognition. At first, ultrasonic NDT (Non Destructive Testing) detection method is introduced and the characteristic of the echo signal is discussed. And then, the wavelet transform is used to process echo signals, the low-frequency energy and the high-frequency energy are extracted as characteristics of echo signal in time-frequency domain. At last, a fuzzy pattern recognition algorithm is designed to evaluate the bonding quality of the composite material, it is based on the maximum membership degree principle. Simulation proved that the algorithm can recognize different echo signals quantitatively and effectively.