Adhesion behavior of polymer networks with tailored mechanical properties using spherical and flat contacts
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Adhesion behavior of polymer networks with tailored mechanical properties using spherical and flat contacts Nishant Lakhera, Department of Mechanical Engineering, University of Wyoming, Laramie, Wyoming 82071 Annalena Graucob, INM—Leibniz Institute for New Materials, Functional Surfaces Group, 66123 Saarbrücken, Germany Andreas S. Schneider, INM—Leibniz Institute for New Materials, Metallic Microstructures Group, 66123 Saarbrücken, Germany Elmar Kroner and Maurizio Micciché, Functional Surfaces Group, INM—Leibniz Institute for New Materials, 66123 Saarbrücken, Germany Eduard Arzt, Functional Surfaces Group, INM—Leibniz Institute for New Materials, 66123 Saarbrücken, Germany; Metallic Microstructures Group, INM— Leibniz Institute for New Materials, 66123 Saarbrücken, Germany; and Saarland University, 66123 Saarbrücken, Germany Carl P. Frick, Department of Mechanical Engineering, University of Wyoming, Laramie, Wyoming 82071 Address all correspondence to Elmar Kroner at [email protected] (Received 29 November 2012; accepted 23 January 2013)
Abstract Four acrylate-based networks were developed such that they possessed similar glass transition temperature (∼− 37 °C) but varied in material stiffness at room temperature by an order of magnitude (2–12 MPa). Thermo-mechanical and adhesion testing were performed to investigate the effect of elastic modulus on adhesion profiles of the developed samples. Adhesion experiments with a spherical probe revealed no dependency of the pull-off force on material modulus as predicted by the Johnson, Kendall, and Roberts theory. Results obtained using a flat probe showed that the pull-off force increases linearly with an increase in the material modulus, which matches very well with Kendall’s theory.
Introduction Normal adhesion testing is a widely used technique for determining adhesive contact between two surfaces. This testing technique most typically involves bringing a probe of known geometry in contact with a flat sample, applying a normal preload, and then retracting the probe until separation occurs.[1–5] The most common approach is to utilize a hard, spherical probe to determine the adhesive properties of a soft, flat specimen.[6–11] The spherical nature of the probe makes testing relatively insensitive to slight misalignment, although the increasing contact area with increasing preload complicates data interpretation. A theoretical solution of the contact between spherical objects was developed by Johnson, Kendall, and Roberts (so called “JKR” theory),[3] and has been widely accepted to describe the adhesive behavior of a clean, smooth, elastic surface, showing no hysteresis in the loading–unloading paths.[12] Another commonly used probe geometry is a flat probe; the contact area beneath a flat probe is insensitive to the preload force, and the theory describing the adhesive behavior (often simply referred to as “Kendall” theory) is well-established.[2] Unfortunately, flat probe testing is infrequently used relative to spherical probes because of the practical
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