Concise analysis of wave propagation using the spectral element method and identification of delamination in CF/EP composite beams

This paper presents a two-dimensional spectral element method for characterizing wave propagation in composite beam structures for the purpose of damage detection. The interaction of Lamb waves with delamination in an 8-ply carbon fiber/epoxy (CF/EP) laminate is investigated, and some unique mechanisms of interaction between Lamb wave modes and delamination are revealed in detail. It is demonstrated that the reflection at the far end of the delamination is much stronger in magnitude than that from the near end, and when the delamination length is comparable to the wavelength of the wave mode, the reflections from both ends of the delamination merge into one. The fundamental antisymmetric (A(0)) mode is more suitable for identification of delamination in multilayered composite structures than the fundamental symmetric (S-0) mode, especially when the delamination is in the symmetric plane. The curves of the reflection coefficient and transmission coefficient are analyzed, showing an undulating shape, and the values of reflection or transmission coefficient are dependent on the ratio of the delamination length to the wavelength of the Lamb wave. A quantitative identification method for delamination in composite beam structures is proposed and validated using an experimental study.