Materials Science and Engineering Division, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA.
Soft Matter. 2017 Oct 4;13(38):6761-6769. doi: 10.1039/c7sm00950j.
Material extrusion (ME) is a layer-by-layer additive manufacturing process that is now used in personal and commercial production where prototyping and customization are required. However, parts produced from ME frequently exhibit poor mechanical performance relative to those from traditional means; moreover, fundamental knowledge of the factors leading to development of inter-layer strength in this highly non-isothermal process is limited. In this work, we seek to understand the development of inter-layer weld strength from the perspective of polymer interdiffusion under conditions of rapidly changing mobility. Our framework centers around three interrelated components: in situ thermal measurements (via infrared imaging), temperature dependent molecular processes (via rheology), and mechanical testing (via mode III fracture). We develop the concept of an equivalent isothermal weld time and test its relationship to fracture energy. For the printing conditions studied the equivalent isothermal weld time for T = 230 °C ranged from 0.1 ms to 100 ms. The results of these analysis provide a basis for optimizing inter-layer strength, the limitations of the ME process, and guide development of new materials.
材料挤出（ME）是一种逐层添加制造工艺，现已应用于需要原型制作和定制的个人和商业生产中。然而，与传统方法相比，ME 生产的零件通常表现出较差的机械性能；此外，对于这种高度非等温过程中导致层间强度发展的基本原理知识有限。在这项工作中，我们从快速变化的流动性下聚合物互扩散的角度来理解层间焊接强度的发展。我们的框架围绕三个相互关联的组件展开：原位热测量（通过红外成像）、温度相关的分子过程（通过流变学）和机械测试（通过模式 III 断裂）。我们提出了等效等温焊接时间的概念，并测试了其与断裂能的关系。对于研究的打印条件，T=230°C 时的等效等温焊接时间范围为 0.1 ms 至 100 ms。这些分析的结果为优化层间强度、ME 工艺的局限性提供了基础，并为新材料的开发提供了指导。
