DMREF: Predictive Multiscale Modeling of the Mechanical Properties of Polymers 3D Printed Using Fused Filament Fabrication

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This Designing Materials to Revolutionize and Engineer Our Future (DMREF) grant will provide new scientific understanding of the Fused Filament Fabrication (FFF) process and its effect on the underlying molecular structure and properties of 3D-printed polymers. 3D-printing is driving a paradigm shift in the design and manufacturing of objects both in every day life and in high-tech applications. The integration with computer-aided design allows printed parts to be customized quickly and inexpensively to meet unique specifications and provide new functionalities. FFF is the most widely used and fastest growing 3D process and FFF printers dominate the growing desktop 3D printing market, driven by the low cost and relative simplicity of the printer construction and wide availability of feedstock materials. Although widely used, applications of FFF printed materials are limited by modest strength and toughness and large variability in material properties. This award supports fundamental research to understand how the printing conditions affect the materials properties of polymers printed by FFF. This fundamental knowledge is needed to advance the application of FFF to structure-critical components, provide computational tools to accelerate the design of FFF printed parts, and develop the next generation 3D-printing technology for polymers. Thus, the outcomes of this project will benefit the US economy. This project will also provide opportunities for undergraduate and graduate students to participate in multidisciplinary research that involves close interactions with national laboratories and product design researchers, and create innovative outreach actives for K-12 on the science and engineering of 3D-printing. The research objective of this project is to uncover the relationships between important printing parameters and feedstock material properties and the anisotropy, strength, and toughness of the printed material. We will develop an integrative research approach with iterative feedback between printing, modeling, and experiments at multiple length scales to investigate: 1) the molecular orientation of the extruded fiber, 2) the nonequilibrium structure and anisotropic, viscoplastic behavior of the annealed fiber, 3) the entanglement structure, strength and toughness of the fiber-fiber weld, 4) the anisotropic viscoplastic and damage behavior of the raster structure, and 5) the thermal history and residual stresses in the printed part. Finally, we will apply the experimentally-validated multi-scale modeling framework to design the properties of feedstock material and printing parameters to improve the strength and toughness of the printed part.