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Journal Club for July 2019: Cohesive strength, interfacial toughness, and their roles in the adhesion of ice

M D Thouless's picture

 

We (K. Golovin, A. Dhyani, M. D. Thouless and A. Tuteja) have recently published an article on the delamination of ice (Science, 364, 371- 375 (2019).  From the perspective of the ice community, this paper is significant because it introduces the notion that design of ice-resistant coatings can require consid- eration of the interfacial toughness between the coating and ice, rather than the interfacial strength that is traditionally considered by the community. From the perspective of the mechanics community, trained to think in terms of fracture mechanics, the paper is significant because it reminds one of the transition between conditions when the failure of interfaces is controlled by cohesive strength, and when it is controlled by interfacial toughness.

The approach described in this paper is rooted in a cohesive-zone under- standing of fracture, which incorporates both strength and toughness pa- rameters. An analysis from this perspective shows that there is a critical length of bonded interface below which strength controls delamination, and above which toughness controls delamination. Experimental observations on the delamination of ice from various coatings illustrate this transition, and reveal situations where it is either control of interfacial strength or of tough- ness that affects the ease with which ice can be shed from a coating. 

 

A discussion of this paper can be found in the attached PDF file 

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PDF icon i-Mechancia-19-07-09.pdf1.46 MB

Comments

Cai Shengqiang's picture

Dear Dr. Thouless, 

Really nice work. Congratulations! I am fully convienced and very happy to know that understanding fracture mechanics is really important for deicing. 

With the similar mechanics background is fiber fragmentation test in single-fiber composite for measuring interfacial strength. It is an another elegant experiment in my mind. 

Best, 

shengqiang

 

 

M D Thouless's picture

One of the troubles with the fiber-fragmentation test is that not everyone who uses it may realize that one can get mutliple cracks in fibers, films and laminates even when there is no sliding at the interface.

Yes, if the problem is such that the inteface slides, then the test can give a shear strength.  However, fracture mechanics with only toughness, and no strength parameter, can also give fragmentation lengths.

One needs to be much more careful than I have sometimes seen to determine whether it is toughness or strength controlling the fragmentation.

This is of course, not to say that the fragmentation test isn't useful; it is to say that I have seen it used without being convinced that authors have fully appreciated possible ambiguities.

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