Sizing of delamination using time-of-flight of the fundamental symmetric Lamb modes

In this study, a procedure is devised, using the fundamental symmetric Lamb mode (So) to estimate the size of an impact-induced delamination at the bottom interface of a composite laminate, which has been subjected to a low-velocity impact. When S o mode incidents at the edge of delamination, it propagates independently in 0° layer and the rest of layers. Based on the propagation of So mode in the delaminated region, an expression is derived, which can estimate the size of interface delamination using measured arrival times or Time-of-Flight (ToF) of So modes. Numerical simulations were carried out on glass/epoxy (GFRP) cross-ply laminates ([0/902] s) to confirm the derived expression and eventually it was validated through experiments carried out on [0/90/0] GFRP laminates. Moreover, the minimum detectable size of delamination through the proposed method was estimated analytically and verified through numerical simulations.

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