Effects of Fluid Cavity Modeling When Predicting Compressive Strength of FDM Printed Nylon With Varying Infill Pattern and Density

Improved simulations are created to mimic the nature of compressive failure related to macro-structure and loading direction in fuse deposition modeling (FDM) additively manufactured nylon parts. Unlike prior work, the simulations incorporate internal fluid cavities to model the effects of entrapped gas within the internal geometric voids. Until now, such modeling technique has only been applied in simulations involving polymer foams. Experimental tests are also conducted to provide a baseline comparisons. The nylon FDM specimens studied vary in terms of infill pattern (hexagonal, triangular, and rectilinear) and infill density. Compressive loads are applied in orthogonal part directions to examine degree of anisotropic compressive strength at onset of permanent deformation. A comparative simulation study with and without the fluid cavity modeling reveals how the accuracy of the results improves when the effects of the entrapped gas is included. The aim of the work is to help establish an improved general method for creating simulations of sufficient fidelity to predict part macro-strengths for various 3D printed infill patterns and densities without the need for time-consuming experimental analyses for every variation in geometry.