The remarkable increase in the flow resistance of dense suspensions can hinder 3D-printing processes on account of flow cessation in the extruder, and filament fragility/rupture following deposition. Understanding the nature of rheological changes that occur is critical to manipulate flow conditions or to dose flow modifiers for 3D-printing. Therefore, this paper elucidates the influences of clay particulates on controlling flow cessation and the shape stability of dense cementing suspensions that typically feature poor printability. A rope coiling method was implemented with varying stand-off distances to probe the buckling stability and tendency to fracture of dense suspensions that undergo stretching and bending during deposition. The contributions of flocculation and short-term percolation due to the kinetics of structure formation to deformation rate were deconvoluted using a stepped isostress method. It is shown that the shear stress indicates a divergence with a power-law scaling when the particle volume fraction approaches the jamming limit; φ → φj ≈ φmax. Such a power-law divergence of the shear stress decreases by a factor of 10 with increasing clay dosage. Such behavior in clay-containing suspensions arises from a decrease in the relative packing fraction (φ/φmax) and the formation of fractally-architected aggregates with stronger interparticle interactions, whose uniform arrangement controls flow cessation in the extruder and suspension homogeneity, thereby imparting greater buckling stability. The outcomes offer new insights for assessing/improving the extrudability and printability behavior during slurry-based 3D-printing process.

中文翻译：

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粘土颗粒如何影响停止流动和屈服应力匹配的胶结悬浮液的卷取稳定性。

由于挤出机中流动的停止以及沉积后长丝的脆性/断裂，致密悬浮液的流动阻力的显着增加会阻碍3D打印过程。了解发生的流变变化的性质对于操纵流动条件或为3D打印确定流量调节剂至关重要。因此，本文阐明了粘土颗粒对控制流动性和致密胶凝悬浮液的形状稳定性（通常具有较差的可印刷性）的影响。实施了一种绕线距离不同的绕线方法，以探测在沉积过程中经历拉伸和弯曲的致密悬浮液的屈曲稳定性和断裂趋势。使用分步等应力法对由于结构形成动力学引起的絮凝和短期渗透对变形速率的影响进行了反褶积。结果表明，当颗粒体积分数接近干扰极限时，剪应力表明其与幂律尺度成正比。φ→φj≈φmax 随着粘土用量的增加，剪切应力的幂律散度减小了10倍。含粘土悬浮液中的这种行为是由于相对堆积率的降低（φ/φmax）和形成具有较强颗粒间相互作用的分形构筑的聚集体所致，其均匀排列控制了挤出机中的流动停止和悬浮液的均质性，从而赋予了更大的稳定性。屈曲稳定性。