Quantitative study of shear modulus and interfacial shear strength by combining modulated lateral force and magnetic force modulation microscopies

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Abstract
Atomic force microscopy (AFM) is currently used to map the qualitative differences of surface properties and is becoming a technique to determine quantitatively the friction and elastic properties, although measurements often are very delicate and need a lot of precaution. A few studies have attempted to determine quantitatively the interfacial shear strength from friction measurements but they require the Young's modulus or the shear modulus to be known. To our knowledge, the shear modulus has never been determined directly by AFM. We propose here a method for measuring this by combining modulated lateral force microscopy (MLFM) and magnetic force modulation microscopy (MFMM), without the need to determine the Young's modulus. The method involves measurements of normal contact stiffness by MFMM and lateral contact stiffness by MLFM, and the use of mechanical contact theory. Once the shear modulus is known, it is possible to determine the shear strength from friction force and lateral contact stiffness measurements by studying its dependence on mean contact pressure. The method is tested on high‐ and low‐density polyethylene and measurements of shear modulus and shear strength are given. Copyright © 2001 John Wiley & Sons, Ltd.