Damage Identification in Composite Beam Using Continuous Wavelet Transform Applied to Mode Shape and Strain Energy Data

The objective of this work is to show the effectiveness of using continuous wavelet transform of modal data to detect, locate and quantify small. local damage in laminated composite beam. This method is based on distribution of maximum absolute wavelet coefficients by applying spatial wavelet transform to the fundamental displacement and strain energy mode shape along the length of beam obtained through ANSYS 8.0. The damage simulating a delamination element is modeled as degradation of stiffness within specific composite layers. For small delamination, the damage-induced changes of natural frequencies and mode shapes are too small to be detected practically. The proposed method processes the modal data so as to even detect very small delamination. The results obtained show that the process of wavelet transformed strain energy mode shape is much more sensitive to smallest damage compared to other conventional methods. Damage extent is investigated in terms of Hoelder exponent, which is estimated by plotting the decay behavior of maximum absolute wavelet coefficients at different scales. It is shown that the magnitude of Hoelder exponent is linked to damage extent. One of the main advantage of proposed methods is that there is no need to have undamaged (baseline) data as required by existing methods of on-line structural health monitoring of complex structures or structures with pre-existing damage.