Santosh Kapuria, Ph.D.
Damage Detection in Laminated Structures using Wavelet Transformation of Global Response
Detection of localized damages in structures through active and nondestructive means, especially in inaccessible areas, is a generic and as yet unresolved challenge before the engineering community. This has led to the development of the general area of structural health monitoring (SHM). In laminated composite structures, where most failures occur due to delamination, early detection of such damages is essential for enhancing their reliability. Traditional vibration signature based methods, such as the changes in natural frequencies and mode shapes due to the presence of damages, are inadequate in detecting such local delamination/transverse crack type damages, since the vibration responses are not very sensitive to these damages. However, it will be shown in this talk that wavelet transformation of mode shapes can be effectively used to extract features that show the presence, location and extent of such damages up to a fairly small size. The methodology will be illustrated through a number of examples involving laminated beams and plates with different types of damages. The structural boundaries introduce distortions in the wavelet transforms, which can be reduced by using various smoothing techniques. Various types of wavelets are compared for their efficacy. The advantage of this method is that it is model independent and does not require prior knowledge of material properties or state of stress in the structures, nor does it require any baseline reference signature. Some preliminary experimental results show an encouraging trend.