Damage detection of laminated composite beams with progressive wavelet transforms

Abstract

ABSTRACT In this study, a newly-developed technique, so-called “integrated wavelet transform (IWT)”, is applied to damage detection of laminated composite beams. The novel IWT technique combines advantages of stationary wavelet transform (SWT) and continuous wavelet transform (CWT) to improve the robustness of wavelet-based modal analysis in damage detection. Two progressive wavelet analysis steps are considered, in which the SWT-based multi-resolution analysis (MRA) is first employed to refine the retrieved mode shapes, followed by the CWT-based multiscale analysis (MSA) to magnify the effect of slight abnormality. The SWT-MRA is utilized to eliminate random noise and regular interferences, separate multiple component signal, and thus extract purer damage information; while the CWT-MSA is employed to smoothen, differentiate or suppress polynomial of mode shapes to magnify the effect of abnormality. The effectiveness of IWT in damage detection is illustrated using the vibration mode shape data acquired from the experimental testing of a cantilever laminated composite beam with a through-width crack. As demonstrated in the successful detection of a crack in composite beams, the progressive wavelet transform analysis using IWT provides a robust and viable technique to identify minor damage in a relatively lower signal-to-noise ratio environment. Keywords: Vibration mode shape, wavelet analysis, integrated wavelet transform (IWT), smart piezoelectric sensors and actuators, crack, beams