Numerical simulation of the edge stress singularity and the adhesion strength for compliant mushroom fibrils adhered to rigid substrates

Balijepalli, Ram Gopal; Begley, Matthew R.; Fleck, N.A.; McMeeking, Robert M.; Arzt, Eduard

doi:10.1016/j.ijsolstr.2016.02.018

Cited by 77 publications

(89 citation statements)

References 36 publications

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“…Similar detachment mechanisms have been reported for mushroom structures by Micciché et al 42 and Heepe et al 43 Also in these studies, the tip geometry modification reduced the propensity for edge cracks induced by corner stress singularities, while a transition to center cracks was induced. 44−46 A more detailed numerical study on the interfacial stress distribution and, in particular, on the intensity of the corner stress singularities as a function of the composite design parameters is currently underway. 47 In addition to the variation of the interfacial stress distribution, reduced pressure inside the cavities upon center crack formation might contribute to the adhesion.…”

Section: Discussionmentioning

confidence: 99%

Composite Pillars with a Tunable Interface for Adhesion to Rough Substrates

Fischer

Arzt

Hensel

2016

ACS Appl. Mater. Interfaces

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The benefits of synthetic fibrillar dry adhesives for temporary and reversible attachment to hard objects with smooth surfaces have been successfully demonstrated in previous studies. However, surface roughness induces a dramatic reduction in pull-off stresses and necessarily requires revised design concepts. Toward this aim, we introduce cylindrical two-phase single pillars, which are composed of a mechanically stiff stalk and a soft tip layer. Adhesion to smooth and rough substrates is shown to exceed that of conventional pillar structures. The adhesion characteristics can be tuned by varying the thickness of the soft tip layer, the ratio of the Young’s moduli and the curvature of the interface between the two phases. For rough substrates, adhesion values similar to those obtained on smooth substrates were achieved. Our concept of composite pillars overcomes current practical limitations caused by surface roughness and opens up fields of application where roughness is omnipresent.

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Section: Discussionmentioning

confidence: 99%

Composite Pillars with a Tunable Interface for Adhesion to Rough Substrates

Fischer

Arzt

Hensel

2016

ACS Appl. Mater. Interfaces

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“…Flat‐ended cylindrical fibrils possess a stress concentration at their perimeter rendering the prevalence of edge defects particularly detrimental to strength . Inclusion of a flange at the tip, creating a “mushroom” fibril geometry, reduces the severity of the edge stress concentration and thus provides protection against edge‐nucleated detachment. More recently similar results have been obtained through use of composite material fibrils with a soft tip layer…”

Section: Introductionmentioning

confidence: 99%

Benefit of Backing‐Layer Compliance in Fibrillar Adhesive Patches—Resistance to Peel Propagation in the Presence of Interfacial Misalignment

Booth

Bacca

McMeeking

et al. 2018

Adv Materials Inter

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Investigations of backing‐layer effects in bioinspired fibrillar adhesives have shown that increased compliance is detrimental to the strength of fibril arrays under normal loading due to an increase in severity of a circumferential load concentration. In this work, the impact of misalignment on the performance of fibrillar adhesive patches contacting smooth flat surfaces is examined, demonstrating that the conditions for circumferential detachment are extremely limited. For an array of fibrils on a backing layer of varying thickness, normal adhesion tests are performed against a flat surface that maintains a fixed angle of misalignment with respect to the adhesive surface. In the aligned state the detachment is circumferential and the detachment force is highest for the thinnest, least compliant backing layer. However, for misalignment angles on the order of just 0.1°, peel‐like detachments are observed. The thickest backing layer, being 210% more compliant than the thinnest, yields a 43% increase in the adhesive strength at a misalignment angle of 0.4°. This suggests that out‐with conditions of precise alignment, backing‐layer compliance is beneficial to strength under normal loading. A mechanical model is presented, revealing the mechanism behind enhanced resistance to peel propagation is deformation of the backing layer at the detachment front which reduces differential stretching of fibrils.

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“…For example, the adhesion can be optimized by controlling the size and shape of the fiber cap [2–3]; this mushroom-shaped microstructure can provide a stronger adhesive performance than the flat punch [4–5]. The compliant fiber is known to increase the strength of adhesion [6–7].…”

Section: Introductionmentioning

confidence: 99%

Adhesive contact of rough brushes

Li¹,

Popov²

2018

Beilstein J. Nanotechnol.

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The adhesive contact between a rough brush-like structure and an elastic half-space is numerically simulated using the fast Fourier transform (FFT)-based boundary element method and the mesh-dependent detachment criterion of Pohrt and Popov. The problem is of interest in light of the discussion of the role of contact splitting in the adhesion strength of gecko feet and structured biomimetic materials. For rigid brushes, the contact splitting does not enhance adhesion even if all pillars of the brush are positioned at the same height. Introducing statistical scatter of height leads to a further decrease of the maximum adhesive strength. At the same time, the pull-off force becomes dependent on the previously applied compression force and disappears completely at some critical roughness. For roughness with a subcritical value, the pressure dependence of the pull-off force qualitatively follows the known theory of Fuller and Tabor with moderate modification due to finite size effect of the brush.

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Numerical simulation of the edge stress singularity and the adhesion strength for compliant mushroom fibrils adhered to rigid substrates

Cited by 77 publications

References 36 publications

Composite Pillars with a Tunable Interface for Adhesion to Rough Substrates

Composite Pillars with a Tunable Interface for Adhesion to Rough Substrates

Benefit of Backing‐Layer Compliance in Fibrillar Adhesive Patches—Resistance to Peel Propagation in the Presence of Interfacial Misalignment

Adhesive contact of rough brushes

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