Application of the Spectral Analysis in Ultrasonic Quantitative Testing of Bonding Defect of Composite Material

The quantitative testing of bonding defect at interface of composite material is a problem in ultrasonic NDT filed. At present with the wide application of this material the demand for an effective method to increase testing accuracy and stability has become more and more evident. In this paper the ultrasonic echo signals are analyzed in frequency domain and extracted the coefficients of amplitudes attenuation as feature values by using the method of the spectral analysis. Quantitative testing and evaluation have been realized. The detail description of the principle and computing method of the maximum entropy spectral estimation and characteristic values extraction are presented in the paper. The detections to the practical samples were carried out and the results show the samples with different degree of debond flaws can be identified with high accuracy.