Indentation techniques

Another largely unexplored area is the change of dynamics due to the influence of the surface. The dynamic behavior of a latex suspension as a model system for Brownian particles is determined by photon correlation spectroscopy in evanescent wave geometry [130] and reported to differ strongly from the bulk. Little information is available on surface motion and relaxation phenomena of polymers [10, 131]. The softening at the surface of polymer thin films is measured by a mechanical nano-indentation technique [132], where the applied force and the path during the penetration of a thin needle into the surface is carefully determined. Thus the structure, conformation and dynamics of polymer molecules at the free surface is still very much unexplored and only few specific examples have been reported in the literature. 

The two mechanical properties measured most frequently using indentation techniques are the hardness, H, and the elastic modulus, E. A t5pical load-displacement curve of an elastic-plastic sample during and after indentation is presented in Fig. 30, which also serves to define some of the experimental quantities involved in the measurement. 

The nano indentation technique can also be used to measure fracture toughness at small scales, by using the radial crack, which occurs when brittle materials are indented by a sharp indenter [72,73]. Lawn et al. [74] have shown that a simple relationship exists between the fracture toughness, Ag, and the lengths of the radial cracks, c, in the form of ... 

N. Vaidya and B. S. Shah, Absolute Hardness of Phenanthrenedoped Anthracene Single Crystals by Knoop Indentation Technique, Indian J. Phys., 77A, 59 (2003). 

ISO 2039-1 2001 Plastics - Determination of hardness - Part 1 Ball indentation method ISO 2039-2 1987 Plastics - Determination of hardness - Part 2 Rockwell hardness ISO 2439 1997 Flexible cellular polymeric materials - Determination of hardness (indentation technique)... 

Lee H, Mall S, He P, Shi DL, Narasimhadevara S, Yeo-Heung Y, Shanov V, Schulz MJ (2007) Characterization of carbon nanotube/nanofiber-reinforced polymer composites using an instrumented indentation technique. Composites Part B 38 58-65... 

Maensiri, S., Roberts, S.G. (2002), Thermal shock resistance of sintered alumina/silicon carbide nanocomposites evaluated by indentation techniques , J. Am. Ceram. Soc., 85(8), 1971-1978. 

Tancret, E, Osterstock, E (1997), The Vickers indentation technique used to evaluate thermal shock resistance of brittle materials , Scripta. Mater., 37(4), 443 447. 

The bulk densities of all the materials were determined using Archimedes method (AS 1774.5, 1979). The Vickers indentation technique was used to measure the hardness in each case. The applied load in the Vickers hardness tests was 10 kg for silicon nitrides and sialons. However, using the same load produced severe lateral cracking in silicon carbides around indents, which prevented the accurate measurement of the diagonals of indents. Therefore the load was reduced to 0.3 kg for silicon carbide samples. 

Anstis, G.R., etal. (1981), Acritical evaluation of indentation techniques for measuring fracture toughness I, Direct crack measurements , J. Am. Ceram. Soc., 64(9), 533-8. AS 1774.5 (1979), The determination of density, porosity and water absorption , Standards... 

The strength of the fiber-matrix interface is one of the key parameters responsible for the stress-strain behavior and damage tolerance of ceramic composites. Two different types of tests are available to measure the fiber-matrix interfacial properties in fiber-reinforced ceramic composites. The first is based on an indentation technique to either push the individual fiber into or through the matrix. The second test method relies on pulling a single fiber out of a matrix. These methods have been compared59 to one another for a glass matrix material, and yield similar results. 

Tests such as Vickers, Knoop, and Brinell use an indentation technique that impinges a hard tip (e.g., diamond) into the sample with a known load (Figure 2.35a). After a designated period of time, the load is removed, and the indentation area is measured. The hardness, H, is defined as the maximum load, L, divided by the residual indentation area, (Eq. 11). The coefficient, F, varies depending on which indentation method is used. This value (14.229 for Knoop and 1.854 for Vickers)... 

Craig RG, Peyton FA The microhardness of enamel and dentin. J Dent Res 1958 37 661-668. Meredith N, Sherriff M, Setchell DJ, Swanson SAV Measurement of the microhardness and Young s modulus of human enamel and dentine using an indentation technique. Arch Oral Biol 1996 41 539-545. 

Cracks were observed on the top surface and the section surface of the disk with an optical microscope. The microstructure was observed by SEM. The surfaces were polished with diamond paste. The Vickers indentation technique was used to evaluate the direction of residual stress. The residual stresses were calculated by an analytical technique on the assumption of elastic condition [2]. For electrical measurement, Pt electrode was formed on the disk surfaces with Pt paste. The electrical resistivity was measured by two-probe method. 

Gratier, J.P., Experimental pressure solution of halite by an indenter technique. Geophys. Res. Letters 20(15) 1647-1650, 1993. 

G.R.Anstis,P.Chantikul,B.R.Lawn and D.B.Marshall. A critical evaluation of indentation techniques for measureing fracture toughness 1 Direct crack measurements. J.Am.Ceram.Soc., 1981,64[9]533-543... 

In general, the available indentation techniques are based either on scanning force microscopy (SFM) or on dedicated indentation setups providing well-defined tip geometries. The two approaches are described in Sections 8.2.1 and 8.2.2, respectively. Issues related to potential artifacts in IP characterization are discussed in Section 8.3. Finally, examples of epoxy IP characterization by means of SFM-based stiffness mapping as well as depth-sensing micro-indentation (DSI) are given in Sections 8.4.1 and 8.4.2, respectively. 

Some Fundamental Aspects of Interphase Mapping by Indentation Techniques... 

Anstis GR, Chantikul P, Lawn BR, Marshall DB. A critical evaluation of indentation techniques for measuring fracture toughness I direct crack measurements. Journal of the American Ceramic Society 1981 64(9) 533-538. 

ISO 2439. Polymeric materials, cellular flexible—Determination of hardness (indentation technique). 1980. 

Ahn, Y., Chandrasekar, S., and Farris, T.N., 1993, Measurement of residual stresses in machined ceramic using the indentation technique, NIST SP 847, pp. 135-146. 

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