Additive manufactured ULTEM 9085 part qualification and allowable generation

Abstract

Part qualification of additive manufactured polymers has become more important due to the increasing tendency in industrial application of Fused Deposition Modeling (FDM) which yields to quality parts with low cost of manufacturing and high freedom of customization. To reduce printing errors and evaluate fabrication process designs before actual manufacturing, reliable virtual methods are required to model the material, predict part performance, determine the design allowables regarding the variations in material, printing errors and manufacturing facilities. This case study demonstrates thermo-mechanical analysis, print process simulation, allowable generation and validation of FDM based 3D printed ULTEM 9085 material system. A nano assisted micromechanics approach is implemented to predict room temperature mechanical properties of 3D printed material system considering micro voids as inclusion calculated using thermal transport phenomenon. The case study also includes prediction of temperature dependent mechanical properties of FDM printed unfilled ULTEM 9085 material using multi-scale material modeling, cure kinetics and multi-factor technique. From print process modeling point of view, geometrical and pathing error macro size defects, called "bald spot", were calculated and resulted in degradation of both modulus and strength properties in the element scale of the Finite Element Model (FEM). Next, thermal and coupled thermal structural analysis using Multi-scale Progressive Failure Analysis (MS-PFA) were performed to calculate temperature distribution, deformation and residual stress during and after 3D printing process. Finite Element Analysis of service loading integrated with MS-PFA was also performed on virtually 3D printed parts considering residual stress and deformed shape as well as geometrical and pathing errors. The simulation showed excellent agreement with available test data. Also, damage initiation and evolution were predicted as a result of MS-PFA. By performing virtual sampling, the tensile strength allowables and constituents' sensitivities for ULTEM9085 printed in multiple orientations were predicted and validated with NIAR's qualification and Stratasys's equivalency test data. The generic acceptance region for parts printed by RP+M and Stratasys printers were plotted to establish FDM ULTEM9085 generic acceptance region between those two distinguished manufacturing facilities.