3D printing is a revolutionary manufacturing method that allows the productions of engineering parts almost directly from modeling software on a computer. With 3D printing technology, future manufacturing could become vastly efficient. However, it has been reported that the 3D printed parts exhibit anisotropic behaviors in microstructure and mechanical properties, that is, depending on the positions (infill orientations) that the parts are placed on a printer platform, the properties of resultant parts can vary greatly. So far, studies on anisotropic behaviors of 3D printed parts have been mostly limited to the static properties (modulus of elasticity, failure strength, etc.); there is a lack on the understanding of mechanical responses of 3D printed parts under dynamic conditions. In the present study, the anisotropic behaviors of 3D printed parts are investigated from the dynamic aspect. Carbon-fiber reinforced ABS (acrylonitrile butadiene styrene) composite plates are 3D printed at various infill orientations. The plates are tested using a dynamic mechanical tester and the mode frequencies are measured. The plates are further modeled by using finite element method and additional modal characteristics are obtained. It is observed that the changes in orientation of 3D printed infill have resulted in significant changes in the mode frequencies of the composite plates. Depending on the boundary conditions of the plates (top-bottom fixed or left-right fixed), the first mode frequency would exhibit continuous decrease or increase, with a maximum change up to 117%. The changes in orientation in 3D printed infill have also altered the modal shapes of the plates. The modal characteristics, including mode indexes, model lines, etc., have changed dramatically, particularly at higher vibration modes.
