Constitutive relation development for FDM 3D printing materials and simulation of printing direction combination

Due to the forming or curing process, the materials of three-dimensional (3D) printing have periodic mesodefects, which result in complex constitutive relations and anisotropy. Fused deposition modeling (FDM), which is a typical 3D printing process, inevitably introduces stacking pore defects due to the three-dimensional stacking of materials along the printing direction. At present, research focuses on the mechanical properties of materials printed along only one single direction. To consider the possibility of changing the mechanical properties of materials by adjusting the printing direction, the change in the properties of printing materials along the multiple printing direction combinations was analyzed in this paper. First, based on a continuous medium model, the constitutive model proposed by Garzon-Hernandez et al. was considered, and then to improve the prediction accuracy of the model in the plastic stage, a model describing the porosity change rate of porous materials was introduced to obtain better prediction results. Then, the finite element method (FEM) was developed using the new constitutive relation model implemented by the User Defined Material subroutine (USERMAT) into ANSYS software. Second, through the finite element subroutine, the mechanical response of the FDM 3D printing plate with two different printing direction combinations was simulated. The results show that by adjusting the print direction combination of the double-layer FDM 3D printing materials, the materials show a different anisotropy, maximum bearing capacity of tension and shear and buckling resistance