Laser-assisted thermoplastic tape placement: Effects of thermal history and placement speed on wedge peel strength of cf/pa6

Abstract

This paper investigates the effect of tape placement speed and process temperature on the wedge peel strength of unidirectional CF/PA6 laminates manufactured in a laser-assisted tape placement process. Placement trials were performed at three different speeds, 100 mm/s, 200 mm/s and 400 mm/s, with varying process temperatures between 250 °C and 400 °C. The process temperature was increased steadily by 30 °C increments in this range. The wedge peel strength was determined with a wedge with a thickness of 3.2 mm, a wedge angle of 30° and a displacement rate of 1 mm/s. The maximum wedge peel strength (6.99 N/mm) was obtained at a tape placement rate of 100 mm/s and tape temperature set point of 340 °C. At increasing processing speeds the impact of the nip point temperatures reduces. Thus, the scatter of the wedge peel strength values is reduced by 60.8% for doubling the speed and by 67.1% for quadrupling the speed. The effect of the applied polyimide film for the wedge peel testing was found to reduce the process temperature for the third ply. Also, higher process speeds lead to a more evenly distributed temperature history without overshooting in temperature and therefore overheating the incoming tape.