Investigation of ultrasonic welding of CF/PA66 using nylon mesh energy directors

Abstract Carbon fiber reinforced polyamide 66 (CF/PA66) sheets are ultrasonically welded by applying nylon meshes as energy directors (EDs) in this paper. The influence of mesh dimensions is revealed by observing the joint formation process, joint mechanical performance, joint cross‐sectional morphology and joint failure mode. Results show that the joint formation process can be divided into wire flattening stage, ED spread stage, tight bonding stage, and mixing stage. The nylon mesh ED with moderate wire spacing, small wire diameter and small mesh area promotes better weld quality. Welding energy will be dispersed rather than concentrated if the mesh area is too large, resulting in reduced failure load. The joints exhibit two fracture modes: interfacial fracture (IF) and workpiece fracture (WF), and the fracture mode of the joints with nylon mesh EDs transits from IF to WF as the welding energy increases. Highlights Five types of nylon mesh are used as energy directors to join CF/PA66 sheets by ultrasonic welding. The influence of nylon mesh dimensions on the mechanical property and fracture mode of joints is investigated. The formation process of ultrasonically welded joints can be separated into wires flattening stage, ED spread stage, tight bonding stage, and mixing stage.