Delarue Antoine P, McAninch Ian M, Peterson Amy M, Hansen Christopher J
Department of Mechanical Engineering, University of Massachusetts Lowell, Lowell, Massachusetts, USA.
Army Research Directorate, US Army Combat Capabilities Development Command-Army Research Laboratory, Aberdeen Proving Ground, Maryland, USA.
3D Print Addit Manuf. 2024 Oct 22;11(5):e1819-e1828. doi: 10.1089/3dp.2022.0305. eCollection 2024 Oct.
Digital light processing (DLP) is rapidly growing in popularity as an additive manufacturing method for the fabrication of composite structures, and is an effective way to prepare high-resolution filled parts, such as ceramic green parts or composite magnets. Yet, higher solid loadings of resins and the resulting dramatic increases in viscosity limit DLP printing for applications that depend upon maximization of filler content. In this work, we investigate the capacity of a bimodal particle size distribution to enable the printing of a photosensitive resin containing up to 70 vol% of fillers. Formulations with unimodal and bimodal solid loadings ranging from 50 to 72 vol% are prepared and their viscoelastic properties measured through rotational rheometry. The zero-shear viscosity of these formulations is fit with a Krieger-Dougherty model, and the dense random close packing fraction of particles determined from the fit is found to be 76.3 vol%. Parts with fine positive and negative features are printed to evaluate the resolution achievable with highly filled photosensitive resins. The part printed with a 70 vol% formulation shows negative features as small as 860 μm, and positive feature as small as 380 μm. Finally, parts with complex patterns are prepared with previously tested formulations, and thermogravimetric analysis results show that the filler content within the parts remains relatively constant over a 3-h print, with a decrease of 2 vol% of solids for the final printed layers.
数字光处理（DLP）作为一种用于制造复合结构的增材制造方法，正迅速受到欢迎，并且是制备高分辨率填充部件（如陶瓷生坯部件或复合磁体）的有效方法。然而，对于依赖于填料含量最大化的应用，树脂的更高固体含量以及随之而来的粘度急剧增加限制了DLP打印。在这项工作中，我们研究了双峰粒度分布使含高达70体积%填料的光敏树脂得以打印的能力。制备了固体含量范围为50至72体积%的单峰和双峰配方，并通过旋转流变仪测量了它们的粘弹性。这些配方的零剪切粘度用Krieger-Dougherty模型拟合，从拟合中确定的颗粒致密随机密堆积分数为76.3体积%。打印具有精细正负特征的部件以评估高填充光敏树脂可实现的分辨率。用70体积%配方打印的部件显示出小至860μm的负特征和小至380μm的正特征。最后，用先前测试的配方制备具有复杂图案的部件，热重分析结果表明，在3小时的打印过程中，部件内的填料含量保持相对恒定，最终打印层的固体含量减少2体积%。
