Mechanism of folding a fiber bundle in the curved section of 3D printed carbon fiber reinforced plastics

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.