ABSTRACT

Surfaces showing macroscopic adhesion are rare in industry but are abundant in Nature. Adhesion enhancement has been discussed mostly with geometrical systems (e.g. patterned surfaces), more rarely with viscoelasticity, and has the goal of increasing hysteresis and the detachment force at separation. Soft materials are common, and these have viscoelastic properties that result in a rate-dependent increase in toughness. Here the detachment of two half-spaces is studied, one being flat and the other having a dimple in the limit of short-range adhesion and rate-dependent work of adhesion, in the presence of axisymmetric single-scale waviness, which itself results in adhesion enhancement, similarly to the Guduru model of rough spheres. The dimpled surface shows pressure-sensitive adhesion, and when waviness is added, the roughness-induced toughening is enhanced. It is shown that when a rate-dependent work of adhesion is also accounted for, as in the present paper, assuming a power-law dependence of the effective work of adhesion on the crack tip velocity, the two enhancements are not completely multiplicative, as the “viscoelastic” one tends to prevail and indicates a new avenue of research for pressure-sensitive adhesion.

摘要

显示宏观粘附的表面在工业中很少见，但在自然界中却很丰富。附着力增强主要与几何系统（例如图案表面）讨论，很少与粘弹性有关，其目标是增加滞后和分离时的分离力。软材料很常见，它们具有粘弹性，导致韧性随速率增加。这里研究了两个半空间的分离，一个是平的，另一个在短程粘附极限和与速率相关的粘附功的限制下具有凹坑，存在轴对称单尺度波纹，这本身会导致附着力增强，类似于粗糙球体的 Guduru 模型。凹凸的表面表现出压敏粘合力，当加入波纹时，粗糙度引起的增韧增强。结果表明，当还考虑了与速率相关的粘附功时，如本文所述，假设有效粘附功与裂纹尖端速度呈幂律依赖性，则两种增强并不完全相乘，因为“粘弹性”趋于流行，并为压敏粘合提供了一种新的研究途径。