Anisotropic Material Behavior and Design Optimization of 3D Printed Structures

Traditional manufacturing processes such as injection or compression molding are often enclosed and pressurized systems that produce homogenous products. In contrast, 3D printing is exposed to the environment at ambient (or reduced) temperature and atmospheric pressure. Furthermore, the printing process itself is mostly “layered manufacturing”, i.e., it forms a three-dimensional part by laying down successive layers of materials. Those characteristics inevitably lead to an inconsistent microstructure of 3D printed products and thus cause anisotropic mechanical properties. In this paper, the anisotropic behaviors of 3D printed parts were investigated by using both laboratory coupon specimens (bending specimens) and complex engineering structures (A-pillar). Results show that the orientation of the infills of 3D printed parts can significantly influence their mechanical properties. Parts with 0-degree filament orientation are seen to have the most favorable responses, including Young’s modulus, maximum strength, failure strain, and toughness. The findings also suggest that the 3D printed products could be theoretically “designed” or “tailored” by adjusting the infill angles to achieve optimal performance. The 3D printed A-pillar structure has been designed by utilizing the multilayered composite theory through a finite element method. With the mid-plane model, the layers in a 3D printed product can be properly designed and optimized based on given loading conditions. The designs have been evaluated through both computational and physical tests and consistent results have been obtained.