A simple frequency-based delamination detection and localization method without baseline model

This study suggests a novel non-model-based method for structural vibration-based health monitoring for composite laminated beams which utilises only the first natural frequency of the beam in order to detect and localise delamination. The method is based on the application of a static force in different positions along the beam. It is shown that the application of a static force on a damaged beam induces forces that push the delaminated layers together resulting in an increase of stiffness to a maximum when the static force is applied on the top and the middle of the delamination area. This stiffness increase in turn causes changes in the structural natural frequencies. The method does not require the frequency of the beam in its baseline condition. A very simple procedure for damage detection is suggested which uses a static force applied at only three points along the beam to detect and localise delamination. The method is numerically validated for a simply supported beam, using a finite element model of the beam. Our results show that the frequency variation with the change of the force application point can be used to detect, localize and in the same time quantify very precisely single delamination.