Continuum and subcontinuum simulation of FDM process for 4D printed shape memory polymers

Abstract

4D printing of shape memory polymers (SMPs) with the Fused Deposition Modeling (FDM) technique is still a dominant challenge, especially those SMPs having lower glass transition temperatures are prone to higher thermal strains during the FDM printing process. Cross-layer reheating events primarily affect the degree of residual stresses causing warpage, dimensional error, layers delamination, and the final quality of the printed part. The main goal of this study is to enable the successful printing of SMPs within the FDM process with the least possible defects, such as warpage. Initially, the FDM printed SMPs characterization such as temperature-dependent thermophysical properties, thermal history of the printing process, and part-level warpage were measured experimentally. Then the experimentally calibrated properties with complex boundary conditions were embodied into a sequentially coupled finite element modeling and simulation tool of the Abaqus© AM Module to numerically validate the temperature history, residual stresses, and warpage. The built-in interfaces of AM module executed the constitutive equations for the entire process to optimize the residual stresses and warpage to enable successful printing of SMPs. Finally, results have indicated while using optimized design space of SMPs printing, the associated warpage, residual stresses, build, and simulation time reduced up to 80%, 81%, 9%, and 18.5%, respectively. Error percentage results have shown a good agreement with resembling deviations.