The recent technology enables us to fabricate carbon fiber reinforced plastics which have continuous reinforcement fibers using a 3D printer. Arbitrarily curved reinforcement fibers are able to be configured using this technology, and it had been revealed that a fiber bundle is folded in a printing process of a curved section in the previous research. However, this mechanism has not been clarified. The present study, therefore, experimental investigations were conducted to clarify the folding of a fiber bundle in a printing process of a curved section. In addition, the electrical resistance was measured to clarify the effect of folding to fiber breakage. As a result, we concluded that folding of a fiber bundle attribute to positional relation of two forces; adhesive force to the print bed and tensile force from the print nozzle, and change of configuration of fiber bundle in the printing process. This mechanism is verified using the finite element analysis. In addition, fiber breakage was also revealed measuring the electrical resistance of a printed fiber bundle, and this presumably affects the mechanical properties of curved sections.

中文翻译：

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3D打印碳纤维增强塑料弯曲截面中纤维束的折叠机理

最近的技术使我们能够使用 3D 打印机制造具有连续增强纤维的碳纤维增强塑料。使用该技术可以配置任意弯曲的增强纤维，并且在之前的研究中已经揭示了在弯曲部分的印刷过程中折叠纤维束。但是，这种机制尚未阐明。因此，本研究进行了实验研究，以阐明弯曲部分打印过程中纤维束的折叠。此外，测量电阻以阐明折叠对纤维断裂的影响。结果，我们得出结论，纤维束的折叠归因于两个力的位置关系；对打印床的粘附力和来自打印喷嘴的拉力，以及印刷过程中纤维束构型的变化。使用有限元分析验证了该机制。此外，通过测量印刷纤维束的电阻也揭示了纤维断裂，这可能会影响弯曲部分的机械性能。