CFRP Porosity Characterization Method Based on Recursive Quantitative Analysis of Ultrasonic Backscattered Signals

Abstract

The invention relates to a CFRP porosity ultrasonic characterization method based on ultrasonic backscattered signal recurrence quantification analysis, and belongs to the technical field of nondestructive detection. The method comprises the steps that an ultrasonic signal collecting system composed of an ultrasonic flaw detector, a delay block probe and a digital oscilloscope is adopted, an ultrasonic backscattered signal is collected, and phase-space reconstruction is conducted on the ultrasonic backscattered signal. Distance between every two time vectors in a phase space is calculated, a reference threshold value is set, a two-dimensional recursive matrix is obtained, and the two-dimensional recursive matrix is visualized to obtain a Recurrence Plot (RP). An RP graph is subjected to quantitative calculation through RQA quantitative index Recurrence Rate (RR), the correlation between the CFRP porosity P and RR is established finally, RR=aP-1, and characterization of the porosity is achieved. Compared with an ultrasonic attenuation method, the limitation that when a bottom echo does not exist or is weak, the porosity cannot be characterized is overcome through the method, and a good popularization prospect is achieved.

Description

Technical field [0001] The invention relates to a CFRP porosity characterization method based on recursive quantitative analysis of ultrasonic backscatter signals, which belongs to the technical field of nondestructive testing. Background technique [0002] CFRP has the advantages of designable performance, high specific strength and specific rigidity, good fatigue performance, corrosion resistance, and integral molding. It is increasingly used in aerospace and other fields. Porosity is inevitable during the processing and preparation of CFRP, and there is no CFRP without pores. Porosity content is characterized by porosity. Porosity has a great influence on the mechanical properties of CFRP. The study pointed out that for every increase of 1% porosity, the interlayer shear performance of the composite material decreases from 5% to 15%, until the porosity reaches 4%, this rule remains basically unchanged; as the porosity increases, The bending strength gradually decreases. Whe...

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Problems solved by technology

Ultrasonic sound velocity method, ultrasonic acoustic impedance method, etc. have the disadvantages of high resolution requirements of the detection system, low accuracy of sound velocity and density measurement, etc., resulting in low applicability

Ultrasonic attenuation method has the advantages of clear detection principle, simple test method, and less influence by fiber content. It is currently the most commonly used non-destructive testing method for porosity. However, it is limited by the bottom echo. Unusable when present or weak

However, the comparison test block method has low applicability due to the difficulty in making the comparison test block, and the difference in the manufacturing process will lead to the inability to establish a general curve of porosity and ultrasonic attenuation coefficient.

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