Ultrasonic welding of thermoplastic composites with woven mesh energy directors: Enhanced strength and hygrothermal resistance
Dongsheng Yue, Guoqun Zhao, Jiaying Pan, Jiaming Liu, Dong Quan
Abstract
In ultrasonic welding of thermoplastic composites, energy directors (EDs) based on thermoplastic films often exhibit low heat generation efficiency and uneven temperature distribution at the welding interface, which negatively affect weld quality and joint strength. To address these limitations, this study introduces a novel plain-woven mesh ED for the ultrasonic welding of carbon fiber-reinforced PPS (CF/PPS) composites. The influence of welding amplitude and displacement on the welding process and joint quality was systematically investigated based on a single-lap shear test. Additionally, the moisture absorption behavior and mechanical performance degradation, and failure mechanisms of welded joints exposed to hydrothermal environments were also investigated. The results demonstrate that the uniform distribution of filament crossings and open areas in the mesh ED significantly enhances its deformation capability under ultrasonic vibration, leading to improved heat generation efficiency and more uniform temperature distribution at the welding interface. As a result, superior weld quality was achieved. By optimizing process parameters, a low defect level of 1.1 % and a maximum shear strength of 32.6 MPa was obtained for the welded joints. Furthermore, after aging at 80°C and 95% relative humidity for 12 weeks, the joint strength remained unchanged, demonstrating exceptional resistance to hygrothermal aging. These findings highlight the potential of mesh ED to overcome the limitations of traditional film-type ED, significantly enhancing both the performance and durability of ultrasonic-welded thermoplastic composite joints.