Delamination Detection in a Laminated Composite Beam Based on Changes in Natural Frequencies

This paper presents an analytical method for modelling delamination parallel to beam longitudinal axis that can help in solving both forward and inverse problems. For vibration analysis of a beam with internal delamination, it is divided into four segments. The forward problem of determination of frequencies due to a known delamination is solved analytically using the characteristics equation. Case studies are presented and the frequencies are compared with finite element frequencies which show a very good agreement between the two. To solve the inverse problem of locating damage from measured changes in natural frequencies, the characteristic equation is solved. In this paper a simple method to solve the inverse problem has been proposed. The method is fast and inexpensive and it has been validated using input frequency data generated by finite element method for both cantilever and simply supported beams. The predicted axial locations and sizes agree closely with the actual data. The maximum errors are 5 and 6 % in the prediction of location and size respectively for a known interface.