Spring-in Behavior of Crystalline CFRTP Sheet after Thermal U-bending

In this study, to improve dimensional accuracy of thermoformed products for carbon fiber reinforced thermoplastic (CFRTP) sheet, effects of sheet thickness, cooling rate on spring-in behavior are investigated by several thermal U-bending test. Matrix resin of the CFRTP is crystalline polyamide 6 (PA6) and plain woven textiles of carbon fiber is used for reinforcement. As a result, for thick sheet and slow cooling, spring-in angle is smaller. In addition, a revised spring-in prediction formula is proposed by considering crystallinity and cooling rate into coefficient of thermal expansion for precise spring-in prediction. The calculation results are compared with experimental. The proposed prediction formula has higher prediction quality than the conventional.