Integrated Thermodynamic Modeling and Experimental Validation of Process-Induced Distortions in Additively Manufactured Polymers*

Additive manufacturing of thermoplastics induces residual stresses and geometric distortions driven by steep thermal gradients, repeated phase transitions, and spatially varying volumetric shrinkage during layer-by-layer deposition. These effects can compromise dimensional accuracy and reduce the reliability of components intended for demanding biomedical and structural applications. Building on our thermodynamic framework for amorphous and semi-crystalline polymers, we present a unified theoretical, computational, and experimental study to predict and control these process-induced instabilities. The framework is rooted in non-equilibrium continuum mechanics and constrained-mixture theory, modeling the polymer melt as a viscoelastic fluid with entropic elasticity. This formulation captures glass transition, crystallization kinetics, and temperature-dependent volumetric changes that govern the evolution of residual stress and distortion during fused-filament fabrication (FFF).

We implement the constitutive relations in a commercial finite-element environment to perform full three-dimensional simulations of the FFF process for complex geometries, including drug-eluting bioresorbable stents and engineering plates. The simulations track the coupled thermal–mechanical history of each deposited layer, predicting shrinkage and warpage with high spatial resolution. Experiments on polycarbonate plates printed in multiple build orientations provide quantitative verification of the predicted geometric changes, showing close correspondence between computed and measured distortions and highlighting the critical influence of build orientation on dimensional accuracy.

By integrating predictive modeling with targeted experiments, this work establishes a practical pathway to optimize process parameters, reduce dimensional inaccuracies, and enable patient-specific or mission-critical polymer components with improved reliability and extended service life.