Hot-stamping technology for carbon fiber reinforced thermoplastic plates based on electrical resistance heating

In the present work, a hot-stamping system for carbon fiber reinforced thermoplastic (CFRTP) plates based on electrical resistance heating was developed, where CFRTP consisted of polyphenylene and polyacrylonitrile. With the hot-stamping process, a simple hat-shaped sample was made. The heating rate and maximum sample temperature varied depending on the electrical resistance of the CFRTP plate. Moreover, the contact conditions between the electrodes and the CFRTP plate also affected the sample temperature owing to their influence on the electrical resistance, which was determined by the amount of exposed carbon fiber (CF) on the sample surface. Temperature measurements performed using samples with various amounts of exposed CF (20%–95% CF) revealed that approximately 65% CF afforded the highest sample temperature and fastest heating rate. The CFRTP plate underwent non-uniform heating, especially during the early stages, e.g. less than 10 s. Sample heating to 150℃ resulted in permanent deformation of the hat-shaped CFRTP samples with less springback, whereas heating to higher temperatures above the melting point led to meandering of the samples. In contrast, CFRTP samples subjected to hot-stamping at lower temperatures, such as 110℃, exhibited rough surfaces. In addition to the sample temperature, the formability of CFRTP during hot-stamping was affected by the holding time. When hot-stamping was performed without a holding time, even at high temperatures of 150℃ and above, low-quality samples with dented surfaces and irregular sample thickness were obtained. The results of this study indicate that a temperature of 150℃ and a holding time of 10 s are optimal for fabricating high-quality hot-stamped CFRTP with smooth surfaces and uniform thickness.