Mechanical anisotropy in polymer composites produced by material extrusion additive manufacturing
Mechanical anisotropy in polymer composites produced by material extrusion additive manufacturing
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DOI：
10.1016/j.addma.2020.101385
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发表时间：
2020-08-01
影响因子：
11
通讯作者：
Compton, Brett G.
中科院分区：
文献类型：
--
作者：
Hmeidat, Nadim S.;Pack, Robert C.;Compton, Brett G.
基于挤出的增材制造技术，例如填充聚合物树脂的直接墨水书写，已经显示出开发具有卓越结构和功能特性的印刷组件的巨大潜力。然而，当高纵横比填充材料通过沉积喷嘴挤出时，相关的挤出过程会导致它们发生择优取向，从而导致打印组件出现强烈的机械各向异性。打印引起的各向异性是一个关键问题，它使增材制造组件的简单设计变得复杂化。这项工作的目标是通过研究填料形态和打印参数对打印复合材料机械性能的影响，更好地了解打印聚合物复合材料的各向异性。油墨的配制使用气相二氧化硅颗粒或纳米粘土片作为主要增粘剂，并使用碳化硅 (SiC) 晶须作为主要机械增强剂。机械各向异性通过使用气相二氧化硅或纳米粘土（有或没有 SiC 晶须）的环氧树脂油墨配方的 3 点弯曲测试来表征，并使用三种不同的喷嘴尺寸以三种不同的打印速度进行打印。纳米粘土的取向也可以使用小角度和广角 X 射线散射来表征。结果表明，当使用纳米粘土或 SiC 填料时，较小的喷嘴直径和较高的沉积速率会导致更大的各向异性，而单独使用气相二氧化硅会导致与打印参数和打印路径无关的机械行为。当平行于打印方向进行测试时，SiC 晶须增强复合材料可获得高达 215 MPa 的优异弯曲强度值。
Extrusion-based additive manufacturing technologies, such as direct ink writing of filled polymer resins, have shown a great potential for the development of printed components with superior structural and functional properties. However, the associated extrusion process induces preferred orientation on high-aspect-ratio filler materials as they extrude through the deposition nozzle, causing strong mechanical anisotropy in printed components. Printing-induced anisotropy is a critical issue that complicates the straightforward design of additively manufactured components. The goal of this work is to gain a better understanding of the anisotropy in printed polymer composites by investigating the effects of filler morphology and print parameters on the mechanical properties of printed composites. Inks are formulated using fumed silica particles or nanoclay platelets as the primary viscosifying agent, and silicon carbide (SiC) whiskers as the primary mechanical reinforcement. Mechanical anisotropy is characterized via 3pt-flexural tests for epoxy ink formulations utilizing fumed silica or nanoclay, with or without SiC whiskers, and printed at three different print speeds, using three different nozzle sizes. Orientation of nanoclay is also characterized using small- and wide-angle x-ray scattering. Results show that smaller nozzle diameters and higher deposition rates lead to greater anisotropy when nanoclay or SiC fillers are utilized, while the use of fumed silica alone results in mechanical behavior that is independent of print parameters and print path. Superior flexure strength values up to 215 MPa are obtained with SiC whisker-reinforced composites when tested parallel to the print direction.