Cure monitoring through time-frequency analysis of guided ultrasonic waves

Cure monitoring has received considerable interest for industrial applications that use thermosetting resins and advanced composites. In these applications, the degree of curing is critical for the structures' high quality and performance. This paper demonstrates the excitation of Lamb waves with low profile surface mounted piezoelectric transducers for the characterisation of symmetric composite laminates at different cure levels. The response signals were processed by extracting their instantaneous characteristics through ensemble empirical mode decomposition. The paper investigates the potential benefit from the use of piezoelectric transducers, which could monitor the life cycle of complex composite structures from the early manufacturing stages to the later aging stages. In these stages, structural monitoring is essential for the prevention of possible catastrophic damage. The response signals successfully captured the different cure levels, and the employed analysis showed good agreement with the increasing cure degree.