Techniques and considerations for nanoindentation measurements of polymer thin film constitutive properties

Strojny, A.; Xia, Xingchuan; Tsou, Andy H.; Gerberich, William W.

doi:10.1163/156856198x00452

Cited by 55 publications

(40 citation statements)

References 15 publications

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“…The unloading load-displacement data thus obtained were used to determine the elastic modulus based on classical indentation theory introduced by Boussing (reviewed in Ref. [23]), simplified by Sneddon [24], and generalized by Pharr et al [25]. According to this theory, a material experiences elastic recovery during the first 25% of the unloading portion of the loaddisplacement curve.…”

Section: Nanomechanical Testingmentioning

confidence: 99%

Effects of polar solvents on the fracture resistance of dentin: role of water hydration

et al. 2005

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Although healthy dentin is invariably hydrated in vivo, from a perspective of examining the mechanisms of fracture in dentin, it is interesting to consider the role of water hydration. Furthermore, it is feasible that exposure to certain polar solvents, e.g., those found in clinical adhesives, can induce dehydration. In the present study, in vitro deformation and fracture experiments, the latter involving a resistance-curve (R-curve) approach (i.e., toughness evolution with crack extension), were conducted in order to assess changes in the constitutive and fracture behavior induced by three common solvents-acetone, ethanol and methanol. In addition, nanoindentation-based experiments were performed to evaluate the deformation behavior at the level of individual collagen fibers and ultraviolet Raman spectroscopy to evaluate changes in bonding. The results indicate a reversible effect of chemical dehydration, with increased fracture resistance, strength, and stiffness associated with lower hydrogen bonding ability of the solvent. These results are analyzed both in terms of intrinsic and extrinsic toughening phenomena to further understand the micromechanisms of fracture in dentin and the specific role of water hydration.

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Section: Nanomechanical Testingmentioning

confidence: 99%

Effects of polar solvents on the fracture resistance of dentin: role of water hydration

et al. 2005

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“…2(c)]. The unloading data are used to determine the mechanical properties based on classical indentation theory introduced by Boussinesq, 15 simplified by Sneddon, 16 and generalized by Pharr et al 17 According to this theory, a material experiences elastic recovery during the first 25% of the unloading phase of the load-unload curve. The slope (dP/dh) where P is the load and h is the indentation displacement, is used to determine the stiffness S of the material, from which the reduced elastic modulus is determined using Equations (1) and (2) as follows: …”

Section: Nanoindentation Of the Ultrasectioned Samplesmentioning

confidence: 99%

Ultrastructure and nanomechanical properties of cementum dentin junction

Balooch

Goodis

et al. 2003

J Biomedical Materials Res

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The attachment between cementum and dentin has been given several definitions and nomenclature, including: interzonal layer, intermediate cementum, collagen hiatus, Hopewell-Smith's hyaline layer, and more commonly, cementum-dentin junction (CDJ). Understanding the attachment of two structurally dissimilar hard tissues such as cementum and dentin defined by a junction may provide information necessary to engineer functionally graded materials that can be used for efficient tooth restorations in clinical dentistry and other bioengineering applications. Hence, in this study, as a first step toward understanding the CDJ using a biomechanical approach, it was hypothesized that the CDJ between cementum and dentin is a wide zone with mechanical properties significantly lower than the neighboring tissues. The structure of the CDJ was studied using an atomic force microscope (AFM), and site-specific mechanical response of the three regions; cementum, CDJ, and dentin were determined using an AFM-nanoindenter under dry and wet conditions. The AFM results of the CDJ demonstrated a valley under dry conditions and a peak under wet conditions. The magnitude of the depth of the valley was approximately the same as the height of the peak of the CDJ, ranging from 10 to 40 microm. The nanomechanical properties under dry conditions indicated no significant difference (p > 0.05) in elastic modulus and hardness of the CDJ (Er = 17.5 +/- 2.7 GPa, H = 0.6 +/- 0.1 GPa) and cementum (Er = 18.7 +/- 2.5 GPa, H = 0.6 +/- 0.1 GPa). The mechanical properties of the CDJ were significantly lower (p << 0.05) than dentin (Er = 19.9 +/- 2.9 GPa, H = 0.6 +/- 0.1 GPa) under dry conditions. However, under more relevant hydrated conditions, the mechanical properties of CDJ (Er 3.0 +/- 0.7 GPa, H = 0.1 +/- 0.0 GPa) were significantly lower (p << 0.05) than those of cementum (Er 6.8 +/- 1.9 GPa, H = 0.2 +/- 0.1 GPa) and dentin (Er 9.4 +/- 2.3 GPa, H = 0.3 +/- 0.1 GPa). Based on the results from this study, it can be concluded that the CDJ can be regarded as a wide zone containing large quantities of proteins including collagen that contribute to hydration and significantly reduce mechanical properties, compared with the adjacent hard tissues, cementum, and dentin. The lower mechanical properties of the CDJ may make it possible for it to redistribute occlusal loads to the alveolar bone.

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“…This geometrical confinement is especially characterized by a high level of hydrostatic pressure, which some materials such as polymers are known to be sensitive to. As a matter of fact, some recent nanoindentation experiments using polymer coatings and pyramidal or conical indenters show that, when the indentation depth becomes of the order of magnitude of the film thickness, the above mentioned indentation models can provide erroneous [8] or unexpectedly high values of the layer Young's modulus [9]. The question thus arises to establish whether such results are the consequence of some limitations of the models under confined contacts situations or they are hydrostatic pressure effects, as it is argued in references [8][9][10][11].…”

Section: Introductionmentioning

confidence: 99%

Measurement of the mechanical properties of thin films mechanically confined within contacts

et al. 2006

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This study addresses the problem of the measurement of the mechanical properties of thin films using contact mechanics methods. In a first stage, an analytical contact model recently developed by Perriot and Barthel [A. Perriot and Barthel, E. J. Mat. Res, 2004. 19(2): 600-608] is used to derive a first order approximation within the limits of confined geometries. Together with indentation experiments using polymer films on elastic substrates, this approach demonstrates the essentially oedometric nature of the coating's response, provided it is not to close to incompressibility. In a second stage, an extension of this approximate description to lateral contact loading allowed to relate the contact stiffness to the shear modulus of the film. This approach was successfully applied to the determination of the viscoelastic modulus of an acrylate polymer film in the glass transition zone of the film, with an emphasis on its sensitivity to hydrostatic pressure. This study suggests that lateral contact experiments are more appropriate than indentation ones for the measurement of film properties close to incompressibility.

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Techniques and considerations for nanoindentation measurements of polymer thin film constitutive properties

Cited by 55 publications

References 15 publications

Effects of polar solvents on the fracture resistance of dentin: role of water hydration

Effects of polar solvents on the fracture resistance of dentin: role of water hydration

Ultrastructure and nanomechanical properties of cementum dentin junction

Measurement of the mechanical properties of thin films mechanically confined within contacts

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