Online Inspection of Weld Quality in Ultrasonic Welding of Carbon Fiber/Polyamide 66 without Energy Directors

In this study, a method of inspecting the weld quality (i.e., static strength) in ultrasonic welding of 4-mm-(0.16-in.-)thick carbon fiber/polyamide 66 (C f / PA66) composite with 30 wt-% fiber without energy directors was investigated.The transient horn displacements and dissipated powers were recorded to correlate with the weld quality.It was found that the transient horn displacement of the joint during the ultrasonic welding process displayed four distinct stages: C f /PA66 expansion phase (stage I), unsteady melting phase (stage II), equilibrium phase of the materials melting and melt outflow (stage III), and the material cooling down phase (stage IV).The weld quality was closely related to the horn displacement and duration in stage III of the ultrasonic welding process.Target horn displacement and duration in stage III were determined by desired static strengths of the welded 4-mm-(0.16-in.-)thick C f /PA66 composite.The horn displacements and durations of the welds in stage III were recorded and the measurements were compared with the target values during welding.A quality weld was determined by judging whether the measured values of horn displacement and duration in stage III were within the tolerance range of the target values.Consequently, an online inspection method to evaluate the weld quality was developed based on target horn displacement and duration.