Cross-wavelet analysis for Lamb wave damage detection in composite materials using optical fibres

In this paper, a cross-wavelet analysis is proposed to enhance the visibility and interpretation of Lamb wave data features related to defects in a composite plate. The study involves a simple experiment on a carbon fibre composite plate interrogated using ultrasonic Lamb waves and incorporating an optical fibre receiver. A fundamental symmetric (S-o) Lamb wave was introduced into the plate using a conventional piezoelectric transducer operating at a frequency range of around 250 kHz. Coupling was achieved using a perspex phase-matching wedge. The propagating acoustic pulses were monitored using a simple surface-mounted single mode optical fibre forming the signal arm of an optical fibre Mach-Zehnder interferometer.