FEM investigation of the temperature field of energy director during ultrasonic welding of PEEK composites

In this study, a finite element model of ultrasonic welding of continuous carbon fiber (CF) reinforced polyetheretherketone (PEEK) laminates is established based on the viscoelastic dissipation theory. The impacts of the size and apex angle of the energy director on the heating process during ultrasonic welding are discussed. Simulation results show that the apex angle of the energy director has a more significant effect on the temperature rising rate than size of the energy director. The apex angle also greatly affects the temperature field profile of the energy director. The highest temperature region of energy directors with 30 and 60 degrees apex angle presents a butterfly shape and deviates a distance from the lower laminate. The 'wings' of the highest temperature region of the 90 degrees energy director nearly merge together and make contact with the lower laminate. The highest temperature region of 120 degrees energy director becomes a closed ellipse area but is wrapped in the energy director tip. As the cross-sectional area of the energy director is smaller than 0.25 mm(2), the heated region on the energy director and lower laminate decreases with the cross-sectional area. As the cross-sectional area exceeds 0.25 mm(2), the heated area on the energy director and lower laminate remains constant. Therefore, an energy director with a 90 degrees apex angle and about 0.25 mm(2) cross-sectional area may be the most suitable for ultrasonic welding of CF/PEEK laminates.