Deep penetrating eddy current testing for visualization of internal defects in CFRP

2021 Fiscal Year Final Research Report

• Project/Area Number: 19K14844
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 18010:Mechanics of materials and materials-related
• Research Institution: Ehime University
• Principal Investigator: Mizukami Koichi 愛媛大学, 理工学研究科(工学系), 講師 (20794019)
• Project Period (FY): 2019-04-01 – 2022-03-31
• Keywords: 複合材料 / 非破壊検査 / 渦電流試験 / 炭素繊維

Outline of Final Research Achievements

This study proposed eddy current testing methods for detection and quantification of delamination and fiber waviness in CFRP. Inhomogeneity of conductivity in CFRP is often problematic in eddy current testing because it causes signal variation even in non-defective zone. Moreover, conventional testing methods are limited to inspection of near-surface region. In this study, the effect of the variation of conductivity in CFRP on eddy current sensor signal was investigated. We successfully developed an eddy current probe and signal processing methods that enable visualization and characterization of deep-lying delamination and waviness without being masked by signal variation in non-defective zone.

Free Research Field

複合材料工学

Academic Significance and Societal Importance of the Research Achievements

軽量かつ高強度な材料である炭素繊維強化プラスチック(CFRP)の製造時や使用時に発生する欠陥，損傷を検出しその寸法を推定するための渦電流試験技術を開発した．渦電流試験は非接触で大面積を高速で検査可能な手法であるが，従来法は非均質材料であるCFRP内の導電性のばらつきの影響を受けやすく，かつ材料の深部にある欠陥，損傷の検出が難しいという課題があった．本研究では，導電性のばらつきによる信号変化に影響を受けにくく，より深部まで感度よく検査可能な試験法や信号処理法を調査し，CFRPの強度低下につながる層間はく離と繊維うねりを明瞭に可視化できるようにした．また，それらの寸法推定手法を構築した．