Locating damage in circular cylindrical composite shells based on frequency sensitivities and mode shapes

This paper presents a feasibility study on locating damage in circular cylindrical fiber-reinforced composite shells based on natural frequencies and mode shape information at specific locations. The axial position of the damage is located by comparing the measured and the predicted frequency changes due to introducing damage. The theoretical frequency changes are approximated by frequency sensitivities. The advantage is that a damaged shell model is not required, as frequency sensitivities are readily obtained from a defect-free finite element model. As the shells are axisymmetric, additional information on mode shape is employed to locate the exact damage position. Results from simulations showed that the proposed detection scheme can easily locate damage in free–free and simply-supported shells. For a clamped-free shell, a successful detection scheme is secured by excluding those vibration modes with a highly nonlinear response to the severity of damage. The robustness of the proposed method in the presence of both modelling and measurement errors is demonstrated by simulation.