NOVEL PROCEDURE OF INTEGRATING TRANSDUCERS TO THERMOPLASTIC COMPOSITE STRUCTURES BY INDUCTION HEATING FOR SHM

Kurzfassung

A novel method of bonding special PZT transducers called Acousto-ultrasonic composite transducers (AUCTs) to high-performance thermoplastic (TP) composites was developed using induction heating. A TP adhesive film (TPAF) is placed between the AUCT and the host composite where a localized induction field is applied to generate heat, while the adherents are kept in contact by pressure until cooling to form a bond. The proposed method is a very fast, economical, and reparable bonding procedure while at the same time reducing the heat exposure of the host structure by using localized heating. Different types of susceptors were used to study if they can contribute to the overall heating of the TPAF. The results showed that the susceptors used in the study do not contribute positively to the heat generated and the best case would be not using a susceptor at all. The influence of various induction process parameters namely power, coupling distance, and time on temperature produced was studied. It was observed that power has the most influence on the temperature produced. Coupling distance is also a very critical parameter. These parameters can be used to get a better control of the process since it is very challenging to exactly control the heating or cooling cycle of the TPAF in an induction heating process. The bonding quality of the AUCTs bonded with induction heating was studied by electro-mechanical impedance (EMI) spectroscopy, it was seen that good bonding quality can be achieved. The mechanical performance of the induction bonded AUCTs was studied by 4-pt static flexural and tensile-tensile fatigue tests. From the static flexural tests, the critical strain measured at gauge for the two TPAFs used were: 0.6% for P45200 and 0.4% for T-Link. From the fatigue tests, it was seen that among the five TPAFs tested, only two do not have a good fatigue tolerance