Free vibration analysis of a cantilever composite beam with multiple cracks

This study is an investigation of the effects of cracks on the dynamical characteristics of a cantilever composite beam, made of graphite fibre-reinforced polyamide. The finite element and the component mode synthesis methods are used to model the problem. The cantilever composite beam divided into several components from the crack sections. Stiffness decreases due to cracks are derived from the fracture mechanics theory as the inverse of the compliance matrix calculated with the proper stress intensity factors and strain energy release rate expressions. The effects of the location and depth of the cracks, and the volume fraction and orientation of the fibre on the natural frequencies and mode shapes of the beam with transverse non-propagating open cracks, are explored. The results of the study lead to conclusions that, presented method is adequate for the vibration analysis of cracked cantilever composite beams, and by using the drop in the natural frequencies and the change in the mode shapes, the presence and nature of cracks in a structure can be detected.