Effect of ultrasonic embossing and welding time on the joint performance of ultrasonically welded short carbon fiber reinforced PEEK

Ultrasonic plastic welding (UPW) is a highly efficient and environmental friendly method that has gained gradually increased attention in joining carbon fiber reinforced thermoplastic (CFRTP). A crucial aspect in UPW of CFRTP is the design of the energy director (ED). This paper employs ultrasonic embossing, a cost-effective way to manufacture ED on the surface of CFRTP sheets. The effect of ultrasonic embossing time and welding time on the joint performance is investigated in terms of microstructure, tensile-shear property, and fracture surface morphology. The results show that the structured surface made by ultrasonic embossing can be used as ED to concentrate welding energy. This process reduces the randomness and dispersion of weld distribution, improves the failure load of welded joints by 30 % compared with the joints made without using ED. The ultrasonic embossing time has a limited influence on the joint failure load. Sound welded joints can be obtained when welding with one structured surface and welding time of 1.5 s.