Journal
INTERNATIONAL JOURNAL OF THERMOPHYSICS
Volume 39, Issue 8, Pages -Publisher
SPRINGER/PLENUM PUBLISHERS
DOI: 10.1007/s10765-018-2416-x
Keywords
Barker code; Carbon fiber reinforced polymer (CFRP); Cross-correlation; Nondestructive inspection; Pulse compression
Funding
- Foundation for Innovative Research Groups of the National Nature Science Foundation of China [51521003]
- Chinese National Natural Science Foundation [61571153, 51173034]
- Self-planned Task of State Key Laboratory of Robotics and System (HIT)
- Programme of Introducing Talents of Discipline of Universities [B07108]
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In this paper, a Barker-coded thermal wave imaging approach is reported on the detection of carbon fiber reinforced polymer (CFRP) laminate with subsurface defects, using an integrated Barker code sequence and sinusoidal carrier-modulated laser as the excitation source. Artificial flat bottom holes as subsurface defects are prepared for the experimental investigation. Cross-correlation (CC) algorithm is applied for extracting characteristics of thermal wave signal and forming the corresponding peak delay time and phase images. The effects of Barker code sequence length and carrier-modulated frequency are investigated, which are both most important factors on the detectability of BC-TWI method. The results of the experiments show 5-bit Barker code and 0.1 Hz carrier frequency are the most suitable selection for enhancing inspection capability and obtaining the highest image SNR for a given CFRP laminate material. Furthermore, a comparative experiment is carried out between BC-TWI and lock-in thermography (LIT) method by taking the defect contrast and SNR into account. The results indicate that the BC-TWI CC phase image has higher contrast and SNR than the LIT phase image.
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