Experimental evaluation of variable thickness 3D printing of continuous carbon fiber-reinforced composites

Abstract

Conventional 3D printers automatically create complex continuous carbon fiber-reinforced polymer (CFRP) composite structures with excellent specific strength and specific stiffness. However, such printing is performed at a constant thickness, which neither provides design freedom in the thickness direction nor an optimal arrangement of CFRP filaments. This study experimentally verified a high-degree-of-freedom 3D printing method in which the layer thickness and path width were controlled by changing the nozzle height during the CFRP printing. From the basic verification of changing the layer thickness, the range where the thickness change is possible was determined. In addition, the fiber orientation and layer thickness were optimized based on the stress distribution for the open-hole tensile problem. Three types of specimens based on constant-thickness straight-line (CTSL) model, optimized fiber path model, and optimized fiber path and thickness (OFPT) model, were prepared and their weight and tensile properties were evaluated. The results showed that the OFPT model successfully reduced the weight by 4.51% and increased the strength by 15.3% compared to the CTSL model.