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

这项旨在革新和设计我们未来的设计材料(DMREF)基金将为熔丝制造(FFF)工艺及其对3D打印聚合物潜在分子结构和性能的影响提供新的科学理解。3D打印正在推动日常生活和高科技应用中物体设计和制造的范式转变。与计算机辅助设计的集成使打印部件可以快速、廉价地定制，以满足独特的规格并提供新的功能。FFF是应用最广泛、增长最快的3D工艺，FFF打印机在不断增长的台式3D打印市场中占据主导地位，原因是打印机结构的低成本和相对简单以及原料的广泛可用。尽管FFF印刷材料得到了广泛的应用，但由于强度和韧性不高以及材料性能的较大变异性，其应用受到限制。该奖项支持基础研究，以了解印刷条件如何影响FFF印刷的聚合物的材料性能。需要这些基础知识来推动FFF在结构关键部件上的应用，提供计算工具来加速FFF打印部件的设计，并开发用于聚合物的下一代3D打印技术。因此，该项目的结果将使美国经济受益。该项目还将为本科生和研究生提供参与多学科研究的机会，这些研究涉及与国家实验室和产品设计研究人员的密切互动，并为K-12创建关于3D打印科学和工程的创新外联活动。本项目的研究目标是揭示重要的印刷参数和原料性质以及印刷材料的各向异性、强度和韧性之间的关系。我们将开发一种综合的研究方法，通过印刷、建模和实验在多个长度尺度上的迭代反馈来研究：1)挤出纤维的分子取向，2)退火纤维的非平衡结构和各向异性粘塑性行为，3)纤维-纤维焊接的纠缠结构、强度和韧性，4)栅格结构的各向异性粘塑性和损伤行为，以及5)印刷部件的热历史和残余应力。最后，我们将应用实验验证的多尺度建模框架来设计原料的性质和印刷参数，以提高印刷件的强度和韧性。

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.