In this paper, an NDT method based on modal flexibility curvature matrix was discussed to detect de-
lamination of composite cylinders. The natural frequency and shift values of the composite cylinder are simulated by
modal analysis. The damage of composite cylinder is detected by the calculated axial and circumferential flexibility
curvature matrix. Analysis shows that both axial and circumferential flexibility curvature matrix methods can accurately
identify the location and size of delamination. From the inner wall of the cylinder to the outer wall, the closer the de-
lamination to the outer wall, the more obviously of flexibility curvature mutations, and more easily the delamination to
be detected. And relatively speaking, the mutation of the axial flexibility curvature F c at delaminated location is far
greater than circumferential flexibility curvature F c , so F c is easier to identify delaminations. But due to itself small
mutation at the fixed end boundary, when damage occurs near the fixed end along axis direction, the axial flexibility
curvature F c may cause misjudgment, in this case, the circumferential flexibility curvature F d can be used to identify
damages.