Abstract
The pursuit of mechanical strength in the injection molding of long-fiber-reinforced resins continues to pose major challenges, namely (1) improvement of fiber defibration and fiber distribution and (2) suppression of fiber breakage during the molding machine’s plastication process. In the present study, a new defibration and distribution evaluation mold is developed to quantitatively evaluate the defibration and distribution of long fibers in nozzle-injected resin. A quantitative analysis method using this evaluation mold is proposed for visualizing and observing long-glass-fiber-reinforced resin up to 30 wt % and long carbon fiber-reinforced resin up to 10 wt %. The method, based on the intensity of light transmitted from a backlight source, is also used to evaluate areas of undefibrated fiber pilling and for evaluating the influence of molding conditions on fiber defibration and uniform distribution. The results clarify that fiber distribution non-uniformity can be reduced by improving the concentration adjustment procedure for the dry blending of high-concentration pellets. Additional results show that fiber defibration and distributive uniformity can be improved by applying high back pressure.
Highlights
Using resin in place of metal parts to reduce weight in the context of molding is a key technological trend in the transportation equipment industry, the manufacture of automobile and airplane parts
Fiber breakage and fiber pilling due to incomplete fiber defibration are problems encountered when long-fiber-reinforced resin is injected in an injection molding context
These problems occur during resin material plastication in the heating cylinder [1,2,3,4,5,6,7] and when the resin passes through the narrow flow path of the nozzle through the reciprocating screw’s check-ring [8,9,10,11,12]
Summary
Using resin in place of metal parts to reduce weight in the context of molding is a key technological trend in the transportation equipment industry, the manufacture of automobile and airplane parts. Analyzed carbon fiber reinforced polymer (CFRP) microscopic images using a similar technique [16] These static measurement evaluation methods use molded samples and are, unable to evaluate the defibration and distribution of non-uniform flowing into the mold during the molding process. The promotion of visualization analysis of defibration and distributive uniformity of long carbon fiber and long glass fiber reinforced resin has currently become a critical research topic For this reason, we propose a quantitative method to evaluate the distributive uniformity of long-fiber-reinforced resin extruded from a nozzle and injected into a mold in a reciprocating-screw plastication process. We measure the intensity of light transmitted from a backlight source as a quantitative means of visualizing the defibration and distribution conditions of nozzle-injected long carbon fibers and long glass fibers in the molten resin. This detailed design realizes high resistance to pressure and high sealability for long-fiber-reinforced resin while permitting continuous visualization and observation of the defibration, and distributive uniformity of the fiber, in the resin injected via the nozzle
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