Form Rolling of FRP Thread with Ultrasonic Vibration

The Fiber Orientation and the Hardness after Indentation Forming

Abstract

Several important items such as fiber orientation and hardness, relating to strength of short glass-fiber reinforced nylon (GRP) thread, are investigated over the section of GRP thread profile after hot and ultrasonic indentation forming. It is observed from SEM photograghs that the fibers at crest are aligned quite differently from the thread profiles formed with two methods, while those at root are aligned similarly along with the surface. The hardnesses along the centerlines of crest and root, measured by Micro-Vickers Hardness Measuring Instrument, tend to be lower than those of base material only at surface. Compared with hot indentation forming, it is found that not only indentation force F₁ but also die temperature (forming temperature) T_d, appears lower for ultrasonic indentation forming. It is also observed the flaw remains inside of the thread profile for hot indentation forming even if the die temperature is elevated to a quite high point.