Plasticity and Fracture in Drying Colloidal Films
Plasticity and Fracture in Drying Colloidal Films
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DOI：
10.1103/physrevlett.110.024301
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发表时间：
2013-01-07
影响因子：
8.6
通讯作者：
Routh, Alexander F.
中科院分区：
文献类型：
--
作者：
Goehring, Lucas;Clegg, William J.;Routh, Alexander F.
干燥胶态分散体中的裂纹通常由弹性断裂力学建模，其假设所有应变都是线性的、弹性的和可逆的。我们测试了这一假设在薄膜的硬乳胶，间歇性地阻止蒸发超过干燥的薄膜，从而减轻薄膜应力。本文表明，尽管裂纹尖端的变形具有脆性断裂的某些特征，但当裂纹卸载时，只有20%-30%的裂纹张开度得到缓解。裂纹尖端的原子力显微照片也显示出塑性变形的证据，如微裂纹和颗粒重排。最后，我们提出了一个简单的缩放参数表明，干燥的胶体膜的屈服应力一般是其最大毛细管压力，因此，裂纹周围的塑性应变通常是显着的。这也表明，膜的断裂韧性可以通过降低颗粒间的粘附力来增加。DOI：10.1103/PhysRevLett.110.024301
Cracks in drying colloidal dispersions are typically modeled by elastic fracture mechanics, which assumes that all strains are linear, elastic, and reversible. We tested this assumption in films of a hard latex, by intermittently blocking evaporation over a drying film, thereby relieving the film stress. Here we show that although the deformation around a crack tip has some features of brittle fracture, only 20%-30% of the crack opening is relieved when it is unloaded. Atomic force micrographs of crack tips also show evidence of plastic deformation, such as microcracks and particle rearrangement. Finally, we present a simple scaling argument showing that the yield stress of a drying colloidal film is generally comparable to its maximum capillary pressure, and thus that the plastic strain around a crack will normally be significant. This also suggests that a film's fracture toughness may be increased by decreasing the interparticle adhesion. DOI: 10.1103/PhysRevLett.110.024301