A novel two-level approach to defect detection in braided CFRP using air-coupled ultrasonic testing

Chenchen Zhang; Yinghong Zhang; Dianzi Liu; Xiaojia Zhang; Xianwei Wu; Zhenghua Qian; Xiangyu Li

doi:10.1016/j.ultras.2022.106884

A novel two-level approach to defect detection in braided CFRP using air-coupled ultrasonic testing

Ultrasonics. 2023 Feb:128:106884. doi: 10.1016/j.ultras.2022.106884. Epub 2022 Nov 8.

Authors

Chenchen Zhang¹, Yinghong Zhang², Dianzi Liu³, Xiaojia Zhang⁴, Xianwei Wu¹, Zhenghua Qian⁵, Xiangyu Li⁶

Affiliations

¹ State Key Laboratory of Mechanics and Control of Mechanical Structures, College of Aerospace Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China.
² School of Mechanical and Electrical Engineering, Guilin University of Electronic Technology, Guilin 541004, China.
³ School of Engineering, University of East Anglia, Norwich NR4 7TJ, UK. Electronic address: dianzi.liu@uea.ac.uk.
⁴ CNPC Tubular Goods Research Institute, Xi'an 710077, China.
⁵ State Key Laboratory of Mechanics and Control of Mechanical Structures, College of Aerospace Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China. Electronic address: qianzh@nuaa.edu.cn.
⁶ Applied Mechanics and Structure Safety Key Laboratory of Sichuan Province, School of Mechanics and Engineering, Southwest Jiaotong University, Chengdu 610031, China.

PMID: 36410124
DOI: 10.1016/j.ultras.2022.106884

Abstract

Air-coupled ultrasonic testing and C-scan technique has been increasingly applied to the braided CFRP structures owing to its non-destruction, non-contact and high visualization characteristics. Due to the noise, structural vibration, and airflow in the process of detection, the accuracy of defect identification is easily deteriorated. To address this issue and further determine the relationship between the ultrasonic acoustical pressure attenuation and structural parameters, a novel two-level identification method based on the modified two-dimensional variational mode decomposition (2D-VMD) has been proposed. In the first level, C-scan images have been sparsely decomposed into ensembles of modes by 2D-VMD method. Then, the modes have been screened by mutual information method to realize the reconstruction of new image in the second level. Experimental results have shown that the proposed method has the good ability to identify defects with a minimum detectable diameter of 1-2 mm. It has been noted that the ultrasonic acoustical pressure attenuation has become remarkably higher in the twill weave CFRP than the plain weave CFRP and the ratio of pressure attenuation between two weave types of CFRP has decreased with the defect depth increase. Meanwhile, shadows around defects in C-scan images have been suppressed to a great extent. It has been demonstrated that the capability of denoising has enabled the developed method with the accurate detection in terms of the shape, size, depth and weave type. With these advantages, the proposed method has provided valuable insights into the development of an effective method for defect detection of braided CFRP structures.

Keywords: Air-coupled ultrasonic testing; Braided CFRP; Defect identification; Two-dimensional variational mode decomposition.