Abstract
The paper presents an algorithm to assess damages in composite structures, based on how natural frequencies of weak-axes bending vibration modes change due to damage. The authors have contrived a correlation between the strain energy stored in a segment of a beam-like structure and the frequency change for that mode if damage occurs on that segment. Finding that the dynamic behavior of composite structures can be best modeled using the share model, which consider the bending moment together with lateral displacement and share deformation, we worked out a relation which gives the frequency shift of all bending modes, involving one coefficient depending on the support type. To evaluate damages, we determine analytically the relative frequency shift as ratio between the frequency change and the natural frequency of the undamaged beam, for the more vibration modes, considering a large number of damage scenarios. Comparing these results with that obtained by measurements on the real structure, it is possible to detect and locate damages with high precision. The method was validated by numerous experiments. Keywords: composite materials, fiber reinforcement, damage detection, natural frequency