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| Cross-Sectional Imaging and Defect Evaluation of Composite Repairs Using High-Resolution Ultrasonic Technique |
| LIU Feifei 1, 2 , ZHOU Zhenggan 1 , LIU Songping 2, 3 , YANG Yusen 2, 3 , ZHANG Lianwang 2 |
1. Beihang University, Beijing 100191, China;
2. AVIC Manufacturing Technology Institute, Beijing 100024, China;
3. AVIC Composite Corporation Ltd, Beijing 101300, China |
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Abstract The recovery of composite structure using performance is closely related to the repair quality. Repair quality is associated with defects in repair area. Complex repair behavior and conditions increase the difficulty and uncertainty in non-destructive testing and evaluation (NDT & E) of composite repair. A high-resolution ultrasonic (HU) technique was proposed to characterize carbon-fiber composite repair behaviors and detect defects induced in repair zones. A HU detection system was constructed. The composite repair specimen was manufactured. The time-domain behaviors of the HU signals in repaired area were studied. A series HU experiments were carried out to the repaired specimen using HU cross-sectional imaging technique. The experimental results show that the quality and time-domain resolution of HU echo signals are obviously better than conventional ultrasonic method; the estimated thickness based on the HU signals is close to 0 deviation from its design value for a 4.5mm thick carbon-fiber composite repaired specimen; the detail repair behaviors, such as repaired area, repaired area morphology, repaired bonding interfaces topography, defects and local resin zones in repaired area, internal microstructures, are very clear and intuitively revealed using the HU cross-sectional imaging and image grayscale distributions; the φ 6mm defects located at near the specimen surface and bottom layers and middle depth are detected clearly and intuitively; the imaging resolution is up to the thickness of a single ply (~0.125mm). Thus, it provides a very effective and powerful detection and evaluation for composite repairs, and good practical application has been obtained.
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2021, 
