Wavelet-aided guided wavefield imaging of delaminations in laminated composite plates

Delamination is a commonly encountered type of damage in composite structures, which may lead to degraded performance and even failure of structures. Thus, detection of delaminations is considered a vital task to maintain structural integrity and reliability. This paper presents a delamination imaging method based on the analysis of guided wavefields. The method relies on the fact that delaminations in a structure will cause wavefield anomalies, which in turn can be utilized for the indication of delamination zones. Such anomalies, however, could be easily masked by the major components of the wavefield signals including incident waves from actuators and reflected waves from structural boundaries. To address the problem, one-dimensional wavelet transform (WT) is used to process the wavefields leading to WT wavefields. The WT wavefields can highlight signal anomalies associated with delaminations. A WT wavefield imaging algorithm is first constructed step by step in detecting multiple delaminations in a glass fiber reinforced polymer (GFRP) plate. The algorithm is then successfully used in the imaging of a single delamination zone in a carbon fiber reinforced polymer (CFRP) plate. The locations, sizes, and shapes of the delamination zones in the GFRP and CFRP plates are clearly visualized in the ultimate damage maps. (paper)