Introducing a novel combined power-amplitude control method for continuous ultrasonic welding of CF/LMPAEK composites

The increasing demands for high production rates, reduced costs, and more sustainable aircraft structures encourage the rapid introduction of thermoplastic composites in aerospace applications. A major challenge for their widespread implementation, especially in single-aisle aircraft programs, lies in meeting the required high production rates of up to 80-100 aircraft per month. Fast, automated manufacturing technologies such as thermoforming and welding are therefore essential to enable scalable industrialization. Continuous ultrasonic welding is such a high-speed joining technique. However, for stiff aerospace-grade composites, it remains challenging to achieve uniformly welded seams using current state-of-the-art control methods. This study investigated the potential for improving process robustness and weld quality in continuous ultrasonic welding of CF/LMPAEK adherends made from unidirectional plies by introducing a novel combined power-amplitude control method. Welds were produced using the state-of-the-art constant-amplitude and constant-power control methods, as well as the newly introduced approach, and were compared in terms of power and amplitude responses, heating uniformity, and resulting weld quality. A combined fuzzy power-amplitude control method was developed and implemented. Under the processing conditions investigated in this study, the proposed control method reduced extreme fluctuations in power and amplitude and was associated with improvements in weld strength and weld uniformity. Overall, the findings indicate that combined power-amplitude control is a promising approach for improving the robustness and quality of continuous ultrasonic welding of thermoplastic composites.