Interfacial cavitation

Abstract

Cavitation has long been recognized as a crucial predictor, or precursor, to the ultimate failure of various materials, ranging from ductile metals to soft and biological materials. Traditionally, cavitation in solids is defined as an unstable expansion of a void or a defect within a material. The critical applied load needed to trigger this instability – the critical pressure – is a lengthscale independent material property and has been predicted by numerous theoretical studies for a breadth of constitutive models. While these studies usually assume that cavitation initiates from defects in the bulk of an otherwise homogeneous medium, an alternative and potentially more ubiquitous scenario can occur if the defects are found at interfaces between two distinct media within the body. Such interfaces are becoming increasingly common in modern materials with the use of multi-material composites and layer-by-layer additive manufacturing methods. However, a criterion to determine the threshold for interfacial failure, in analogy to the bulk cavitation limit, has yet to be reported. In this work we fill this gap. Our theoretical model captures a lengthscale independent limit for interfacial cavitation, and is shown to agree with our observations at two distinct lengthscales, via two different experimental systems. To further understand the competition between the two cavitation modes (bulk versus interface) we expand our investigation beyond the elastic response to understand the ensuing unstable propagation of delamination at the interface. A phase diagram summarizes these results, showing regimes in which interfacial failure becomes the dominant mechanism.

Torsion-induced stick-slip phenomena in the delamination of soft adhesives

“…k and G) in such soft material interfaces is complicated by the fact that the material itself undergoes nonlinear deformations prior to sliding or delamination. 29 This explains the spread of reported values in the literature and the ongoing effort to develop new characterization methods. 30 Within this context, the indirect estimates obtained in this work offer an alternative approach.…”

“…Note that directly measuring the surface properties (i.e. k and Γ) in such soft material interfaces is complicated by the fact that the material itself undergoes nonlinear deformations prior to sliding or de-lamination 29 . This explains the spread of reported values in the literature and the ongoing effort to develop new characterization methods 30 .…”

“…In addition, the use of a transparent adhesive and substrate in contact on the cylinder's circular surface (instead of the lateral surface) allows for visual tracking of the delamination process in a way that the tubular joint tests do not. This setup therefore enables us to observe behaviors beyond the initiation of delamination and to capture the effect of nonlinear deformations, which have recently been shown to play a significant role in determining the interfacial toughness of soft adhesives 29,30 .…”

“…This setup therefore enables us to observe behaviors beyond the initiation of delamination and to capture the effect of nonlinear deformations, which have recently been shown to play a significant role in determining the interfacial toughness of soft adhesives. 29,30 Some preliminary research has already been conducted on the cylinder/flat-plate geometry we propose. The linear elastic model created by Pe ´rez-Ra `fols and Nicola 31 considers the initiation of delamination, but did not capture the reattachment and stick-slip behavior.…”

Effect of Polymer Gel Elasticity on Complex Coacervate Phase Behavior

“…where τ is the surface tension of the droplet, R is the radius of the droplet, and P c is the compressive stresses from the polymer network. − These effects have been shown to lead to droplet migration from higher-modulus areas in the gel to lower-modulus regions and have been termed as “elastic ripening.” Rosowski et al found that elastic ripening can be substantial enough to even reverse Ostwald ripening . Using a similar system, Kim et al grew, shrank, and regrew elliptical droplets and found the droplets were more elongated after regrowth, indicating that the gel had sustained damage.…”