In recent years, CFRP have been increasingly used in automotive and aerospace industries due to their high strength, stiffness, and light weight. An interlaminar delamination in CFRP might lead to severe structural integrity loss. Therefore, a non-destructive technique capable of detecting the delamination is highly needed. We investigated the relationship between the spectral response of zero-group velocity (ZGV) Lamb waves and the delamination in CFRP. ZGV Lamb waves were efficiently generated using a slit-array mask with spacing equal to the ZGV Lamb wavelength, based on a method proposed by Frédéric(1). In intact regions, a distinct peak corresponding to the ZGV Lamb waves appeared, while in delaminated areas, this peak was suppressed and low-frequency components around 0.2–0.5 MHz were enhanced. The energy in this frequency band increased over the delaminated zone. The delamination length was estimated as 4 mm, whereas the actual size observed on the cross section was 2.9 mm.
Katayama et al. (Wed,) studied this question.