Investigation of fiber waviness in fused deposition modeling printed continuous fiber-reinforced polymers

Fused deposition modeling (FDM) is a widely used method of 3D printing that can be used to easily create complex polymer parts for a wide variety of industries, but they have inherently low mechanical properties and are not suitable for use in higher load applications. Fiber reinforcement can be added to polymers to produce continuous fiber-reinforced polymers (CFRPs), which significantly improves the stiffness and strength of FDM-printed polymers. Fiber waviness (FW) has been shown to decrease mechanical properties in other forms of CFRPs, but its effect on FDM-printed CFRPs is not well understood. This study aims to determine the association of FW and stiffness for FDM-printed CFRPs, as well as to investigate improving print quality by changing process parameters. The strong negative association found between FW and stiffness indicates that increased FW decreases the stiffness of FDM-printed CFRPs. Additionally, changing the amount of tension applied to the fiber during printing had a significant effect on FW, as does the length of straight fiber paths. Finally, the breaking force and break location on the fibers are determined by factors other than FW. These findings are useful for improving print quality and broadening the application of FDM-printed CFRPs.