Detection study of delamination defects in composite cylinders based on CT scanning and Digital Shear Speckle Interferometry

Carbon fiber reinforced composite hydrogen storage cylinders are the essential components for hydrogen fuel cell vehicles. However, it is still lack of efficient and reliable methods for detecting and evaluating manufacturing defects that occurred in the processing and forming of these cylinders. In this study, industrial CT (Computed Tomography) scanning and digital speckle interferometry experiments based on shearography were conducted on the carbon fiber reinforced composite hydrogen storage cylinders. The experimental results reveal that delaminations are the predominant type of manufacturing defect in the fiber wound layer of the cylinders. By analyzing the local mechanical response characteristics caused by delaminations inside the cylinders, the study elucidates the variation of the interferometry fringes and out-of-plane displacements induced by delaminations with different severity. The regions of fringe pattern with "butterfly shape" captured in shearography are highly consistent with the positions, sizes, and influence ranges of delaminations found by CT scanning within the fiber wound layer. Employing shearography technology in hydrostatic testing provides a strong support for the assessment of the service performance and safety of the cylinders, thus holding significant implications for the development of hydrogen storage equipment.