Study on the behavior of carbon fibers in the kneading process using twin-screw extruders.

Fiber-reinforced thermoplastics (FRTPs) have been used for wide variety of applications due to their high mechanical performance and light weight. The properties of molded FRTPs depend on the fiber length and they increase until the finer length in them reaches a certain length. However, it is difficult to keep the length long in the compounding and molding process avoiding the fiber breakage. Based on the above background, the objective of this study was to predict the degree of fiber breakage and control the fiber length in compounding process using the twin screw extruders. Two different laboratory sizes of extruders were used to observe the carbon fiber length in polypropylene matrix. The screw configurations composed of full-flight screws only and the combinations of right, left, and neutral kneading blocks. In the former case, the fiber breakage was caused by the full-flight screw only, suggesting the screw root depth had a significant effect. In the latter, it was cleared that fiber breakage rate was correlated with the mean shear stress obtained by the 3D numerical simulations. [ABSTRACT FROM AUTHOR]