干燥胶体薄膜中的移动裂纹,Soft Matter

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干燥胶体薄膜中的移动裂纹
Soft Matter ( IF 2.9 ) Pub Date : 2022-02-01 , DOI: 10.1039/d1sm01568k
Atiya Badar ₁ , Mahesh S Tirumkudulu ₁

Affiliation

从油漆和涂料到陶瓷和半导体加工的许多应用中都会遇到干燥胶体膜。在许多情况下，干燥过程中会产生收缩应力，这会使薄膜破裂。虽然以前的许多实验和理论工作都集中在静态裂纹的开裂上，但关于胶体涂层裂纹动力学的研究却很少。在这里，我们为稳定移动的裂纹推导了裂纹尖端附近的应力、位移和压力场的解析解。我们首先考虑两种极端情况，即裂纹运动比达西流速快得多的不排水极限和非常缓慢的裂纹扩展的相反极端，即排水极限。下一个，我们考虑裂纹尖端运动的时间尺度与间隙流动的时间尺度相当的一般情况。结果结合了系统的微观结构细节，包括颗粒体积分数和填料性质，以及颗粒的机械性能，如剪切模量和泊松比。虽然预测结果与脆性材料的结果一致，但预测的裂纹速度至少比实验中观察到的高一个数量级。我们总结了差异的可能原因。虽然预测结果与脆性材料的结果一致，但预测的裂纹速度至少比实验中观察到的高一个数量级。我们总结了差异的可能原因。虽然预测结果与脆性材料的结果一致，但预测的裂纹速度至少比实验中观察到的高一个数量级。我们总结了差异的可能原因。

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Moving cracks in drying colloidal films

Drying colloidal films are encountered in many applications ranging from paints and coatings to ceramic and semiconductor processing. In many cases, shrinkage stresses are generated during drying, which can fracture the film. While much of the previous experimental and theoretical work has focused on cracking in static cracks, there are very few studies on the dynamics of cracks in colloidal coatings. Here, we derive an analytical solution for the stress, displacement, and pressure fields near the crack tip for a steadily moving crack. We consider first the two extreme cases, namely, the undrained limit where the crack motion is much faster than the Darcy flow rate and the opposite extreme of very slow crack propagation, the drained limit. Next, we consider the general case where the timescale for crack-tip motion is comparable to that for the interstitial flow. The results incorporate the micro-structural details of the system including the particle volume fraction and nature of packing, and the mechanical properties of the particles such as shear modulus and Poisson's ratio. While the predicted results are in line with those for brittle materials, the predicted crack speeds are at least an order of magnitude higher than those observed in experiments. We conclude with the possible reasons for the discrepancy.

更新日期：2022-02-01

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