Cole Daniel P, Gardea Frank, Henry Todd C, Seppala Jonathan E, Garboczi Edward J, Migler Kalman D, Shumeyko Christopher M, Westrich Jeffrey R, Orski Sara V, Gair Jeffrey L
Vehicle Technology Directorate, CCDC US Army Research Laboratory, Aberdeen Proving Ground, MD, USA.
Materials Science and Engineering Division, National Institute of Standards and Technology, Gaithersburg, MD, USA.
Integr Mater Manuf Innov. 2020;9(4). doi: 10.1007/s40192-020-00188-y.
Material extrusion (MatEx) is finding increasing applications in additive manufacturing of thermoplastics due to the ease of use and the ability to process disparate polymers. Since part strength is anisotropic and frequently deviates negatively with respect to parts produced by injection molding, an urgent challenge is to predict final properties of parts made through this method. A nascent effort is underway to develop theoretical and computational models of MatEx part properties, but these efforts require comprehensive experimental data for guidance and validation. As part of the AM-Bench framework, we provide here a thorough set of measurements on a model system: polycarbonate printed in a simple rectangular shape. For the precursor material (as-received filament), we perform rheology, gel permeation chromatography, and dynamical mechanical analysis, to ascertain critical material parameters such as molar mass distribution, glass transition, and shear thinning. Following processing, we conduct X-ray computed tomography, scanning electron microscopy, depth sensing indentation, and atomic force microscopy modulus mapping. These measurements provide information related to pores, method of failure, and local modulus variations. Finally, we conduct tensile testing to assess strength and degree of anisotropy of mechanical properties. We find several effects that lead to degradation of tensile properties including the presence of pore networks, poor interfacial bonding, variations in interfacial mechanical behavior between rasters, and variable interaction of the neighboring builds within the melt state. The results provide insight into the processing-structure-property relationships and should serve as benchmarks for the development of mechanical models.
材料挤出（MatEx）因其使用简便以及能够加工不同聚合物，在热塑性塑料的增材制造中得到越来越广泛的应用。由于零件强度具有各向异性，且相对于注塑成型生产的零件，其强度常常呈负偏差，因此，迫切需要解决的挑战是预测通过这种方法制造的零件的最终性能。目前正在初步尝试开发MatEx零件性能的理论和计算模型，但这些工作需要全面的实验数据来指导和验证。作为增材制造基准测试（AM-Bench）框架的一部分，我们在此提供了对一个模型系统的全面测量：以简单矩形形状打印的聚碳酸酯。对于前驱体材料（收到的长丝），我们进行流变学、凝胶渗透色谱和动态力学分析，以确定关键材料参数，如摩尔质量分布、玻璃化转变和剪切变稀。加工后，我们进行X射线计算机断层扫描、扫描电子显微镜、深度传感压痕和原子力显微镜模量映射。这些测量提供了与孔隙、失效方式和局部模量变化相关的信息。最后，我们进行拉伸试验，以评估机械性能的强度和各向异性程度。我们发现了几种导致拉伸性能下降的影响因素，包括孔隙网络的存在、界面粘结不良、光栅之间界面力学行为的变化以及熔体状态下相邻结构之间的可变相互作用。这些结果为加工-结构-性能关系提供了见解，并应作为机械模型开发的基准。
