Testing method for evaluating mechanical properties of 3D printed CFRP with curved fibers by four-point bending test of L-shaped specimen

Abstract

In this study, we propose a method to evaluate the mechanical properties (circumferential fracture stress, circumferential elastic modulus) of 3D printed carbon fiber reinforced plastics with a curved section by a four-point bending test of an L-shaped specimen. Several L-shaped specimens with different radii were printed to evaluate the relation between the radius and mechanical properties. Additionally, the internal structure was observed by X-ray CT, and the fiber orientation angle was examined by cross-sectional observation of the curved section to clarify the fracture mechanism and causes that affect the mechanical properties.In the four-point bending test of the L-shaped specimen, a compressive fracture first occurs at the outer surface of the curved section, and the compressive fracture stress and the elastic modulus decrease with the inner radius are less than 10 mm and 5 mm, respectively. The evaluation of the fiber orientation angle suggests that the decrease in the elastic modulus is caused by the fiber bundle twisting that deviates the fiber direction from the circumferential direction. Furthermore, the fiber breakage and voids generated in the curved section can affect its mechanical properties.

Keywords

• A: Carbon fiber reinforced plastics
• B: 3D printing
• C: Mechanical testing
• D: Curved section