Abstract
Adhesive contact between a flat brush structure with deformable microfibrils and an elastic half space is numerically simulated. The stiffness of pillars is modeled by linear springs. The fast Fourier transform-assisted boundary element method for the contact of rigid indenters is modified to include the microfibril stiffness so that the deflection of pillars and elastic interaction to elastic foundation are coupled. In the limiting case of rigid pillars (pillar stiffness is much larger than the contact stiffness), the adhesive force is determined by the filling factor of brush, as described earlier. In the case of very soft pillars, the adhesive force is proportional to N1/4, where N is the number of pillars. The influence of relative stiffness, number and distribution of pillars on adhesive force is studied numerically. The results from both regularly and randomly distributed pillars show that the adhesive force is enhanced by splitting a compact punch into microfibrils and this effect becomes larger when the fibrils are softer.
Highlights
In the last twenty years, a so-called “contact splitting” has been a popular concept, stating that stronger adhesion can be achieved by dividing a contact surface into small sub-contacts [1].This concept was initially inspired by the observation of the biological adhesive pads of insects and geckos
We numerically study adhesive dry contact between a flat brush structure and an elastic half space taking account of the elastic deformation of pillars
The fast Fourier transform (FFT)-assisted boundary element method (BEM) was further developed to consider the stiffness of pillars in adhesive contact of a soft brush structure
Summary
In the last twenty years, a so-called “contact splitting” has been a popular concept, stating that stronger adhesion can be achieved by dividing a contact surface into small sub-contacts [1]. This concept was initially inspired by the observation of the biological adhesive pads of insects and geckos. There are many theoretical works on the principle of contact splitting and contact mechanics perspectives on fibrillar structures, for example, a JKR (Johnson, Kendall and Roberts) -theory based solution of dividing the indenter into a large number of smaller pillars with a small cap radius [2,7] Contact surfaces below a critical size have been shown to develop a uniform stress distribution at maximum adhesion strength before a complete separation occurs [8]. A detailed review can be found in [2,9,10]
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