Abstract
In molding of carbon fiber reinforced thermoplastics (CFRTP), resin impregnation behavior to fiber yarns is very important because higher viscosity of molten thermoplastics inhibites resin impregnation to the interspace among fibers. Resultant resin un-impregnation causes lower mechanical properties of CFRTP. The purpose of this study was to clarify the relation among molding method, molding conditions and resin impregnation to fiber yarns experimentally and analytically. In this study, CFRTPs using continuous carbon fiber yarn as a reinforcement and a thermoplastic polyimide which is excellent in heat resistance as a matrix resin were produced by Micro-Braiding, Film Stacking and Powder method. In addition resin impregnation was modeled based on Darcy’s law and continuity condition. As a result, analytical resin impregnation prediction showed good agreements with the experimental results in all the producing methods and molding conditions. In addition, the void content in the molded CFRP could be greatly reduced by pressurizing cooling.
Highlights
Since carbon fiber reinforced plastics (CFRP) has excellent characteristics of specific strength and specific stiffness, it has been used in many fields including aerospace
We investigated the effect of molding method and molding conditions on resin impregnation to fiber yarns in carbon fiber reinforced thermoplastics (CFRTP)
We focused on the two-dimensional resin impregnation analysis and analytical resin impregnation prediction was conducted based on the previous research (Kobayashi et al 2017) to discuss the difference in impregnation behavior in different molding methods
Summary
Since carbon fiber reinforced plastics (CFRP) has excellent characteristics of specific strength and specific stiffness, it has been used in many fields including aerospace. The thermosetting resins generally used for CFRP are relatively brittle compared with thermoplastic resins, and is inferior in impact resistance (Lee and Kim 2017). CFRP is generally molded by heat-pressurizing using a semi-cured prepreg sheet impregnated with thermosetting resin to carbon fibers, so that it takes time for polymerization reaction (Svensson et al 1998). Thermoplastic resins have excellent toughness and impact resistance, and are easy to handle as compared with thermosetting resins. Thermoplastics and their composite have superior properties as mentioned above, they have inferior characteristics such as lower resin impregnation to reinforcing fiber yarns. Resin-un-impregnated region, referred as void, exists in the fiber yarns after molding, which fact results in lower mechanical properties
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