Micromechanical properties

Hard layer and soft layer combined together can reduce the intrinsic stress of the whole coating [17,18,22-27]. Samples 4, 5, and 6 have higher critical load than that of monolayer A and B. For Samples 5 and 6, no obvious crack occurs during the scratch test. Sample 5 has the highest hardness and reduced elastic modulus among the multilayer samples, and the interfaces in Sample 5 also contribute to scratch resistance. So it has the best micromechanical properties here. 

Other valuable extensions of contact-mode SFM probe micromechanical properties of the sample. Variation of the repulsive force or upward deflection of the cantilever are registered while a Z-modulation is applied either to the sample or the cantilever base (Fig. 6). The dZ/dZc signal contains information about the local stiffness dF/d.8 of the sample, where S=Zt-Zc is the indentation depth. Micromechanical applications will be discussed in Sect. 2.2. 

When the experimentalist set an ambitious objective to evaluate micromechanical properties quantitatively, he will predictably encounter a few fundamental problems. At first, the continuum description which is usually used in contact mechanics might be not applicable for contact areas as small as 1 -10 nm [116,117]. Secondly, since most of the polymers demonstrate a combination of elastic and viscous behaviour, an appropriate model is required to derive the contact area and the stress field upon indentation a viscoelastic and adhesive sample [116,120]. In this case, the duration of the contact and the scanning rate are not unimportant parameters. Moreover, bending of the cantilever results in a complicated motion of the tip including compression, shear and friction effects [131,132]. Third, plastic or inelastic deformation has to be taken into account in data interpretation. Concerning experimental conditions, the most important is to perform a set of calibrations procedures which includes the (x,y,z) calibration of the piezoelectric transducers, the determination of the spring constants of the cantilever, and the evaluation of the tip shape. The experimentalist has to eliminate surface contamination s and be certain about the chemical composition of the tip and the sample. 

Shroff, S. G., Saner, D. R., and Lai, R. 1995. Dynamic micromechanical properties of cultured rat atrial myocytes measured by atomic force microscopy. Am J Physiol 269, C286-292. 

Burgert, L, K. Fruehmann, J. Keckes, P. Fratzl, and S. E. Stanzl-Tschegg. 2004. Structure-functionrelationships of four compression wood types-Micromechanical properties at the tissue and fiber level. Tree Structure and Function 18 480-485. 

Aim and his coworkers [31] attempted to show macroscopic models can be successfully applied to measure the adhesion forces by AFM. Butt et al. [16] wrote a review on measuring surface forces in an electrolyte solution with 7LFM. Local surface properties like the surface charge density or micromechanical properties can be determined by AFM. 

Weisenhorn et al. [43] studied adhesion, attraction, and repulsion between surfaces in liquids with an atomic force microscope. Their work also shows the usefulness of the AFM for investigations of micromechanical properties. 

A tentative model has been proposed to relate the interfacial shear strength at the fibre-matrix interface, measured by a fragmentation test on single fibre composites, to the level of adhesion between both materials. This last quantity has been estimated from the surface properties of both the fibre and the matrix and was defined as the sum of dispersive and acid-base interactions. This new model clearly indicates that the micromechanical properties of a composites are mainly determined by the level of physical interactions established at the fibre-matrix interface and, in particular, by electron acceptor-donor interactions. Moreover, to a first approximation, our model is able to explain the stress transfer phenomenon through interfacial layers, such as crystalline interphases in semi-crystalline matrices and interphases of reduced mobility in elastomeric matrices. An estimation of the elastic moduli of these interphases can also be proposed. Furthermore, recent work [21] has shown that the level of interfacial adhesion plays a major role on the final performances (tensile, transverse and compressive strengths and strains) of unidirectional carbon fibre-PEEK composites. 

N. Dayma, B.K. Satapathy, Micro structural correlations to micromechanical properties of polyamide-6/low density polyethylene-grafted-maleic anhydride/nanoclay ternary nanocomposites, Materials and Design 33 (1) (2012) 510-522. 

Abramoff B, Klein LC (2005) Elastic Properties of Silica Xerogels. J Am Ceram Soc 73 3466-3469 Moner-Girona M, Roig A, Molins E, Martinez E, Esteve J (1999) Micromechanical properties of silica aerogel. Appl Phys Lett 75 653-655... 

MonCT-Girona, M., A. Roig, E. Molins, E. Martinez, and J. Esteve. 1999. Micromechanical properties of silica aerogels. Applied Physics Letters 75(5) 653-655. 

Maszybrocka J, Cybo J, Frackowiak JE, Krzemiai K. Change of micromechanical properties polymer/metal system. Adv Mater Tech 2006 513 75-84. 

METHACRYLIC ESTER POLYMERS. See Volume 3. MICROCELLULAR PLASTICS. See Volume 7. MICROEMULSION POLYMERIZATION. See Volume 7. MICROGELS. See Smart Materials, Microgels. MICROMECHANICAL PROPERTIES. See Volume 3. MISCIBILITY. See Volume 7. 

Recently, several different techniques to study micromechanical properties have been applied. Besides spectroscopic and scattering techniques, the microscopic techniques of electron microscopy and atomic force microscopy are particularly useful for direct determination of micromechanical properties in polymers (2-7). A brief overview about successfully applicable techniques is given in this article. Using these techniques, micromechanical properties of different polymers that have been studied are also reviewed. 

Additional details of micromechanical properties can be studied using several other techniques. These additional techniques include the following ... 

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