An algorithm based on logarithm of wavenumber amplitude for detection of delamination in carbon fiber composite

Delamination is one of the most common types of damage/defect in carbon/glass fiber reinforced composites and many researchers use frequency-wavenumber analysis to detect delamination. There are large fluctuations in amplitudes when Lamb wave propagates in composite plate, so that it is hard to precisely identify the boundary of delamination simply from the change of wavenumber. This paper has presented an algorithm based on logarithm of wavenumber amplitude to detect the delamination in carbon fiber plate with high precision. In wavenumber spectra after logarithm processing, the wavenumber amplitudes at delamination boundary can be significantly amplified and the resulting curve of sum of amplitudes can be used to effectively identify the boundary. In this paper, the principle of the logarithm of amplitude algorithm has been introduced and the effectiveness of the algorithm in delamination identification has been validated by finite element simulations and physical experiments. Compared with conventional algorithms, the proposed algorithm can effectively identify the boundary with better accuracy (less than 5%) and has decent identification stability under different depths of delamination. Our research has great potential for solving the challenge in precise identification of delamination boundary. (paper)