Guided-Wave Structural Health Monitoring for Assessing the Bond Strength of Induction-Welded Thermoplastic Composite Joints

Abstract This study investigates the interaction between ultrasonic guided waves (GW) propagation and bond quality of induction-welded thermoplastic composite joints. Using ultrasonic piezoelectric transducers, the proposed robust structural health monitoring (SHM) method established a strong correlation between ultrasonic signals and the health status of joint. Three joint batches were manufactured with varying shear strength by adjusting welding parameters. Batch 1 had superior properties, while batches 2 and 3 were intermediate and lower, respectively. Transducers were placed on opposite sides of the joint overlap, operating at 350 kHz and 450 kHz. Time of flight (ToF) measurements, indicating wave group velocity, showed a direct correlation with weld-line stiffness and wave propagation velocity. These findings significantly contribute to the understanding of the interaction between mechanical properties and guided wave propagation in induction-welded thermoplastic composite joints, providing valuable insights for monitoring the performance of such joints in engineering applications.