The main aim of this study is to determine the fracture toughness of printed Polylactic Acid (PLA), Polyethylene Terephthalate Glycol (PETG), PLA reinforced with short carbon fiber (PLA–C), and PETG reinforced by short carbon fiber (PETG-C) specimens. FFF printed specimens exhibit orthotropic behavior, meaning their fracture toughness vary depending on the direction of crack propagation relative to the printed layers. Hence, the single edge notch bending (SENB) specimens were printed in three raster angles leading to determining the interlayers, intralayers, and translayers fracture toughness of the four filament types. Additionally, the influence of loading rates 1, 50, and 500 mm/min on the fracture toughness of all printed specimens were investigated. The results manifested that in the presence of short carbon fiber, the translayers fracture toughness of 3D printed PETG polymer was significantly improved at any loading rate. As the main advantages of the findings of this study, it is suggested to use the short carbon fiber for reinforcing the PETG filament. Besides, when the crack is normal to the printed layers, the fracture toughness of printed PLA and PETG objects have higher fracture toughness
