This paper presents a new laser reflection technique which can identify the near-surface defects in concrete structures bonded with carbon fiber reinforced polymer (CFRP). In this study, a laser beam is used to illuminate the surface of CFRP-concrete panel, and the pattern of the laser reflection is recorded by a high resolution digital camera. Under the laser illumination, the surface of the tested object is heated and expanded. The surface expansion can be identified through observing the expanding reflection pattern. Based on our experimental observation, the defect region exhibits much greater expansion of laser reflection pattern than that in intact region. Results also indicate that both the defect area and the defect depth can influence the change of reflection pattern. In view of the measurement principle of the laser reflection technique, it is expected that the application can be further extended to the areas like CFRP-wood structures, CFRP-masonry structures and CFRP-steel structures.
Qiwen Qiu and Denvid Lau, "Use of laser reflection technique for defect detection in CFRP-concrete systems," Proc. SPIE 9804, Nondestructive Characterization and Monitoring of Advanced Materials, Aerospace, and Civil Infrastructure 2016, 98041C (Presented at SPIE Smart Structures and Materials + Nondestructive Evaluation and Health Monitoring: March 23, 2016; Published: 22 April 2016); https://doi.org/10.1117/12.2218751.
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