Processing and mechanical characterization of short carbon fiber-reinforced epoxy composites for material extrusion additive manufacturing
Processing and mechanical characterization of short carbon fiber-reinforced epoxy composites for material extrusion additive manufacturing
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DOI：
10.1016/j.compositesb.2021.109122
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发表时间：
2021-07-10
影响因子：
13.1
通讯作者：
Compton, Brett G.
中科院分区：
文献类型：
--
作者：
Hmeidat, Nadim S.;Elkins, Daniel S.;Compton, Brett G.
近年来，纤维增强聚合物复合材料被广泛用作材料挤出添加剂制造(AM)工艺的原料，以提高打印部件的强度、刚性和功能，而不是未填充的打印聚合物。然而，纤维增强聚合物复合材料中AM的广泛采用要求对印刷部件中的工艺-结构-性能关系有更深入的了解，而这种关系还没有被很好地理解。纤维长度对短纤维复合材料的力学性能至关重要，但到目前为止，很少有人研究纤维长度分布在复合材料原料加工过程中是如何演变的，以及这种演变如何影响3D打印复合材料的打印行为和力学性能。在这项工作中，测量了碳纤维增强环氧复合材料在广泛的油墨组成和剪切混合时间范围内的FLD，其分布符合威布尔分布函数。研究了FLD对油墨加工性能、油墨流变性、印刷性能和力学性能的影响。此外，还探讨了打印参数(喷嘴尺寸和打印速度)对打印复合材料的力学各向异性和纤维取向分布的影响。通过3pt弯曲试验对印制复合材料的力学性能进行了表征，并利用光学显微镜、扫描电子显微镜(SEM)和X射线计算机层析(CT)对复合材料的微观结构进行了研究。最后，将拟合出的威布尔参数输入到包含FLD和FOD的复合模型中，模型预测结果与实验观测结果吻合较好。
Fiber-reinforced polymer composites have been extensively utilized in recent years as feedstock materials for material extrusion additive manufacturing (AM) processes to improve strength, stiffness, and functionality of printed parts over unfilled printed polymers. However, the widespread adoption of AM of fiber-reinforced polymer composites requires a deeper understanding of the process-structure-property relationships in printed components, and such relationships are not well understood yet. Fiber length is critically important to the mechanical performance of short fiber composites, but very few studies to-date have focused on how the fiber length distribution (FLD) evolves during processing of composite feedstocks and how this evolution affects printing behavior and mechanical properties in 3D-printed composites. In this work, FLD is measured for carbon fiber reinforced epoxy composites over a wide range of ink compositions and shear mixing times, and the distributions are fit with a Weibull-type distribution function. The effects of FLD on the tradeoff between ink processability, ink rheology, printing behavior and mechanical properties are investigated. Furthermore, the effects of printing parameters (nozzle size and print speed) on mechanical anisotropy and fiber orientation distribution (FOD) in printed composites are explored. Mechanical properties of printed composites are characterized via 3 pt-flexural testing, and microstructure is investigated using optical and scanning electron microscopy (SEM), and x-ray computed tomography. Finally, the fitted Weibull parameters are fed into a composite model that incorporates FLD and FOD, and model predictions are found to be in excellent agreement with experimental observations.