Non-Destructive Evaluation for Small Size Defects in Composite Structures using a Hybrid Approach 2019-01-1268

Recently, composite materials/structures are getting increasingly used in the automotive and aerospace industry. Defects issue is commonly associated with the use of composite materials/structures. Reliable Non-Destructive Evaluation (NDE) of composite structures is still challenging due to the existence of small size defects. In this research, a hybrid approach is used to accurately determine small size internal defects. In this hybrid approach, X-Ray Computed Tomography is used as a reference to accurately determine all defect locations, then a digital shearography method is used to conduct fast NDE for in-line testing. The critical shearographic NDE parameters such as shearing angle, shearing distance and loading amount are determined and optimized based on the X-ray CT scan result. The smallest detectable defect size by digital shearography is determined as 0.44mm. From the comparison of X-ray CT scan results and digital shearography NDE results, the detection rate using digital shearography for defects with a size of larger than 1mm is 97.30% (36 detected out of 37) and for defects with a size of 0.4mm – 1mm is 84.48% (49 detected out of 58). The Shearographic NDE fundamentals, optimization of Shearographic NDE parameter, experiment setup, and testing results are shown in detail in this paper.