scholarly journals On the Effect of a Rate-Dependent Work of Adhesion in the Detachment of a Dimpled Surface

2021 ◽  
Vol 11 (7) ◽  
pp. 3107
Author(s):  
Antonio Papangelo
Keyword(s):  
Power Law ◽  
Soft Materials ◽  
Work Of Adhesion ◽  
Patterned Surfaces ◽  
Weak State ◽  
Partial Contact ◽  
Rate Dependent ◽  
Pressure Sensitive ◽  
Full Contact ◽  
Unloading Rate

Patterned surfaces have proven to be a valuable design to enhance adhesion, increasing hysteresis and the detachment stress at pull-off. To obtain high adhesive performance, soft materials are commonly, used, which easily conform to the countersurface, such as soft polymers and elastomers. Such materials are viscoelastic; i.e., they show rate-dependent properties. 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 a power law rate-dependent work of adhesion, as observed by several authors. Literature results have suggested that the dimpled surface would show pressure-sensitive adhesion, showing two possible adhered states, one weak, in partial contact, and one strong when full contact is achieved. By accounting for a power law rate-dependent work of adhesion, the “weak state” may be much stronger than it was in the purely elastic case, and hence the interface may be much more tough to separate. We study the pull-off detachment stress of the dimpled surface, showing that it weakly depends on the preload, but it is strongly affected by the dimensionless unloading rate. Finally, possible implications of the presented results in the detachment of soft materials from rough substrates are discussed.

scholarly journals On the Effect of Shear Loading Rate on Contact Area Shrinking in Adhesive Soft Contacts

2021 ◽  
Vol 69 (2) ◽  
Author(s):  
Antonio Papangelo
Keyword(s):  
Contact Area ◽  
Loading Rate ◽  
Soft Materials ◽  
Shear Loading ◽  
Analytical Models ◽  
Work Of Adhesion ◽  
Rigid Sphere ◽  
Linear Elastic ◽  
Area Reduction ◽  
Rate Dependent

AbstractAdhesion and, its interplay with friction, is central in several engineering applications involving soft contacts. Recently, there has been an incredible push towards a better understanding on how the apparent contact area evolves when a shear load is applied to an adhesive soft contact, both experimentally and theoretically. Although soft materials are well-known to exhibit rate-dependent properties, there is still a lack of understanding in how the loading rate could affect the contact area shrinking. Indeed, most of the experiments involving a sphere-flat contact have been conducted at a fixed loading rate, and, so far, analytical models have assumed a constant work of adhesion, independent on the peeling velocity. Here, by using linear elastic fracture mechanics, an analytical model is derived for the contact of a rigid sphere on a soft adhesive substrate, which is aimed at elucidating the effect that a rate-dependent work of adhesion has on the contact area shrinking. The model results show that contact area reduction is very sensitive to the loading rate, with slower loading rates promoting a stronger shrinking, which seems in agreement with Literature results. Furthermore it is shown that rate effects enhance the apparent interfacial toughness, i.e. more energy is needed to drive the system from full stick up to gross sliding.

Applicability of power law for describing the rheology of soils of different origins and characteristics

2009 ◽  
Vol 46 (9) ◽  
pp. 1011-1023 ◽  
Author(s):  
Sueng Won Jeong ◽  
Serge Leroueil ◽  
Jacques Locat
Keyword(s):  
Strain Rate ◽  
Power Law ◽  
Debris Flows ◽  
Rheological Behaviour ◽  
Strain Rate Range ◽  
Rate Dependent ◽  
Different Origins ◽  
Power Law Index ◽  
Soil Behaviour ◽  
Low Activity

The rate-dependent rheological behaviour of soils of different origins and characteristics was studied and the applicability of the power law model was examined. The studied soils were divided into three groups: (i) low-activity soils, (ii) high-activity soils, and (iii) silt-rich soils. The results show that the power law applies to all these soils and is representative of soil behaviour in a strain rate range corresponding to debris flows, which is generally not the case with the Bingham model. For low-activity clays, the power law index, n, is typically equal to 0.12 and seems to increase with the plasticity index; it is larger (i.e., in the range of 0.2–0.6) for silt-rich soils. Comparison of n values for tests performed on intact and remoulded low-activity clay specimens indicates that the power law index is possibly strain-rate dependent.

scholarly journals Wetting transitions in droplet drying on soft materials

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Julia Gerber ◽  
Tobias Lendenmann ◽  
Hadi Eghlidi ◽  
Thomas M. Schutzius ◽  
Dimos Poulikakos
Keyword(s):  
Contact Line ◽  
Traction Force ◽  
Soft Materials ◽  
Wetting Transition ◽  
Surface Design ◽  
Complex Processes ◽  
Compliant Substrates ◽  
Rate Dependent ◽  
Liquid Removal ◽  
Droplet Drying

Abstract Droplet interactions with compliant materials are familiar, but surprisingly complex processes of importance to the manufacturing, chemical, and garment industries. Despite progress—previous research indicates that mesoscopic substrate deformations can enhance droplet drying or slow down spreading dynamics—our understanding of how the intertwined effects of transient wetting phenomena and substrate deformation affect drying remains incomplete. Here we show that above a critical receding contact line speed during drying, a previously not observed wetting transition occurs. We employ 4D confocal reference-free traction force microscopy (cTFM) to quantify the transient displacement and stress fields with the needed resolution, revealing high and asymmetric local substrate deformations leading to contact line pinning, illustrating a rate-dependent wettability on viscoelastic solids. Our study has significance for understanding the liquid removal mechanism on compliant substrates and for the associated surface design considerations. The developed methodology paves the way to study complex dynamic compliant substrate phenomena.

Nanoindentation Method for Determining the Initial Contact and Adhesion Characteristics of Soft Polydimethylsiloxane

2005 ◽  
Vol 20 (8) ◽  
pp. 2004-2011 ◽  
Author(s):  
Yifang Cao ◽  
Dehua Yang ◽  
Wole Soboyejoy
Keyword(s):  
Indentation Depth ◽  
Contact Point ◽  
Nonlinear Least Squares ◽  
Soft Materials ◽  
Work Of Adhesion ◽  
Contact Radius ◽  
Initial Contact ◽  
Combined Use ◽  
Fitting In ◽  
Load Indentation

In this paper, we present a method for determining the initial contact point and nanoindentation load–indentation depth characteristics for soft materials. The method is applied to the prediction of the load–indentation depth characteristics of polydimethylsiloxane. It involves the combined use of Johnson–Kendall–Roberts and Maugis–Dugdale adhesion theories and nonlinear least squares fitting in the determination of the initial contact point, the transition parameter, and the contact radius at zero contact load. The elastic modulus and the work of adhesion are also extracted from the load–indentation depth curves.

Power-Law Phenomena in Adhesive De-Bonding

1996 ◽  
Vol 458 ◽  
Author(s):  
G. Kendall ◽  
P. J. Cote ◽  
D. Crayon ◽  
F. J. Bonetto
Keyword(s):  
Power Law ◽  
Characteristic Length ◽  
Power Laws ◽  
Structural Features ◽  
Fractal Nature ◽  
Pressure Sensitive Adhesive ◽  
Self Organized ◽  
Pressure Sensitive ◽  
Self Organized Criticality ◽  
Glass Interface

ABSTRACTAcoustic emission (AE) events were recorded during the peeling of pressure-sensitive adhesive (PSA) tape from a silicate glass surface. The distributions of AE event durations and energies are found to have the form of power laws. Power-law dependencies (hyperbolic distributions) are recognized as a consequence of self-organized criticality (SOC), resulting from the absence of any characteristic length or time scales. In these studies, standard optical microscopy was used to characterize the fractal nature of the PSA-glass interface. The present results suggest that it is the inherent static structural features found at the fractal PSA-glass interface which produce the observed hyperbolic distributions in AE events, rather than a true SOC process.

scholarly journals The sliding contact of a rigid wavy surface with a viscoelastic half-space

2014 ◽  
Vol 470 (2169) ◽  
pp. 20140392 ◽  
Author(s):  
N. Menga ◽  
C. Putignano ◽  
G. Carbone ◽  
G. P. Demelio
Keyword(s):  
Half Space ◽  
Applied Load ◽  
Sliding Velocity ◽  
Contact Conditions ◽  
Frictional Properties ◽  
Single Asperity ◽  
Partial Contact ◽  
Pressure Distributions ◽  
Full Contact ◽  
Asperity Contacts

In this paper, the contact of a rigid sinusoid sliding on a viscoelastic half-space is studied. The solution of the problem is obtained by following the path drawn by Hunter for cylindrical contacts. Results show that depending on the remote applied load, a transition from full contact conditions to partial contact may occur depending on the sliding velocity. This effect, which is not observed in smooth single asperity contacts, is related to the viscoelastic stiffening of the material and to the periodicity of the contacts. Frictional properties as well as contact area, displacement and pressure distributions are discussed in detail.

Characteristics of Adhesive Joints under Rate-Dependent Tensile Loading

2014 ◽  
Vol 660 ◽  
pp. 618-622 ◽  
Author(s):  
Mahzan Johar ◽  
King Jye Wong ◽  
Mohd Nasir Tamin
Keyword(s):  
Tensile Load ◽  
Tensile Loading ◽  
Adhesive Joints ◽  
Optimum Level ◽  
Cohesive Failure ◽  
Pressure Sensitive Adhesive ◽  
Loading Rates ◽  
Rate Dependent ◽  
Pressure Sensitive ◽  
Linear Behavior

Effects of loading rates on deformation and mechanical properties of adhesive joints are examined in this study. For this purpose, acrylic foam pressure sensitive adhesive (PSA) was employed with aluminum adherents. Tensile loading of the adhesive joint was applied at displacement rates ranging from 5 to 500 mm/min. Results show that the tensile load-displacement response is characterized by three regimes, namely an initial non-linear behavior with initiation of cavities, a hardening behavior through fibrillation process and the final fracture of the stretched fibrils. The strengths of the adhesive joints increases asymptotically from 0.56 to 1.92 MPa over the displacement rates from 5 to 500 mm/min. Both modulus and strain energy density at fracture reach optimum level around a displacement rate of 100 mm/min. Adhesive failure of the joint dominates at low loading rate (below 10 mm/min.) while cohesive failure is prominent at faster loading rates above 250 mm/min.

Viscoelastic Contact of a Half-Plane Sliding Over a Slightly Wavy Rigid Surface

2014 ◽  
Author(s):  
N. Menga ◽  
C. Putignano ◽  
T. Contursi ◽  
G. Carbone
Keyword(s):  
Contact Problem ◽  
Contact Area ◽  
Analytical Procedure ◽  
Sliding Contact ◽  
Rigid Surface ◽  
Viscoelastic System ◽  
Contact Conditions ◽  
Partial Contact ◽  
Full Contact ◽  
Viscoelastic Contact

In this paper, the sliding contact of a rigid sinusoid over a viscoelastic halfplane is studied by means of an analytical procedure that reduced the original viscoelastic system to an elastic equivalent one, which has been already solved in [1]. In such a way, the solution of the original viscoelastic contact problem requires just to numerically solve a set of two integral equations. Results show the viscoelasticity influence on the solution by means of a detailed analysis of contact area, pressure and displacement distribution. A particular attention is paid to the transition from full contact to partial contact conditions.

Adhesion of Triblock Copolymer-Based Thermoreversible Gels and Pressure Sensitive Adhesives

2000 ◽  
Vol 629 ◽  
Author(s):  
Kenneth R. Shull ◽  
Alfred J. Crosby ◽  
Cynthia M. Flanigan
Keyword(s):  
Elastic Moduli ◽  
Adhesive Layer ◽  
Work Of Adhesion ◽  
Underlying Structure ◽  
Pressure Sensitive Adhesive ◽  
Adhesive Properties ◽  
Pressure Sensitive Adhesives ◽  
Pressure Sensitive ◽  
Surface Development ◽  
Thermoreversible Gels

ABSTRACTTriblock copolymers with poly (methyl methacrylate) (PMMA) end blocks and a poly (n-butyl acrylate) (PnBA) midblock have been synthesized as model pressure sensitive adhesives and thermoreversible gels. These materials dissolve in a variety of alcohols at temperatures above 60 °C to form freely flowing liquids. At lower temperatures the PMMA end-blocks associate so that the solutions form ideally elastic solids. In our case the solvent is 2-ethylhexanol, polymer volume fractions vary from 0.05 to 0.3, and the elastic moduli are close to 10,000 Pa. We have conducted three types of experiments to elucidate the origins of adhesion and bulk mechanical properties of these materials: 1) Weakly adhering gels: The adhesive properties of the gels are dominated by the solvent. Very little adhesion hysteresis is observed in this case, although we do observe hysteresis associated with the frictional response of the layers. 2) Strongly adhering gels. By heating the gels in contact with a PMMA surface, it is possible to bond the gels to the surface. Development of adhesion as the PMMA blocks penetrate into the PMMA substrate can be probed in this case. The cohesive strengths of the gels are found to be substantially greater than their elastic moduli, so that these materials can be reversibly extended to very high strains. These properties have enabled us to probe the origins of elastic shape instabilities that play a very important role in the behavior of thin adhesive layers. 3) Dried gels – model pressure sensitive adhesives. By removing the solvent at low temperatures, the underlying structure of the gel is preserved, giving a thin elastic layer with excellent performance as a pressure sensitive adhesive. Resistance to adhesive failure, expressed as a velocity-dependent fracture energy, greatly exceeds the thermodynamic work of adhesion. This energy is further magnified by ‘bulk’ energy dissipation when the stress applied to the adhesive layer exceeds its yield stress.

Sign in / Sign up

Export Citation Format

Share Document