Acousto-ultrasonic composite transducers (AUCTs), comprising piezoceramic materials in a reinforced polymeric matrix, show promise for structural health monitoring in composite structures. Challenges arise when integrating AUCTs onto highly loaded thermoplastic composites, especially low-surface-energy materials like polyaryletherketone composites. To address this, the study explores the viability of attaching AUCTs to low-melting polyaryletherketone carbon fiber-reinforced thermoplastic composite structures using ultrasonic welding. This welding technique forms a joint where the interface material fuses with the AUCT embedment and the structure matrix, providing a reliable and automatable process. The investigation includes a comparative analysis of an ultrasonic welded joint with an external energy director and a reference AUCT system integrated using a vacuum bagging oven procedure. Results highlight the potential of AUCT configurations integrated by ultrasonic welding as an alternative solution, acknowledging challenges that persist for further development and increased reliability in structural health monitoring applications.

Acousto-ultrasonic composite transducers (AUCT), which are made of piezoceramic materials embedded in a reinforced polymeric matrix, are promising for the health monitoring of composite structures. However, when they are integrated into highly loaded thermoplastic composite structures, ensuring proper joining properties is a challenge. The conventional approach of attaching the AUCT using adhesive may not be sufficiently reliable in aeronautic applications for low surface energy materials such as polyaryletherketone composites, where surface treatments are needed for adhesion. Welding techniques can be used to create a joint in which the interface material interfuses with the AUCT embedment and the structure matrix, resulting in a homogeneous interface with properties comparable to the host structure matrix throughout its service life. With this in mind, the main objective of the present work is to investigate the viability of attaching AUCT to low-melting polyaryletherketone carbon fiber reinforced thermoplastic composite structures using the ultrasonic welding (UW) procedure and characterize the joint performance. The ultrasonic welded joint using an external energy director in the interface is investigated by comparing the findings to those of a reference AUCT system integrated into the structure with autoclave co-consolidation. Infrared thermography is employed to monitor the process, and a parameter study of the UW process is carried out. The AUCT survivability during the UW process is determined by measuring the capacitance, and C-scan is used to assess joint quality. The results show the challenges of attaching AUCT to thermoplastic composite structures using UW and surviving the procedure.