Journal ArticleDOI
Measurement of Creep Compliance of Solid Polymers by Nanoindentation
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TLDR
In this article, a method to measure the local surface creep compliance of time-dependent materials is proposed and validated in the regime of linear viscoelasticity using nanoindentation.Abstract:
Methods to measure the local surface creep compliance of time-dependent materials are proposedand validated in the regime of linear viscoelasticity using nanoindentation. Two different bulkpolymers, Polymethyl Methacrylate (PMMA) and Polycarbonate (PC), were employed in thevalidation study; though it is expected that the methods developed herein can be applied for verysmall amounts of materials and heterogeneous materials. Both Berkovich and sphericalnanoindenters were used to indent into the material in nanoindentation tests. Two loading historieswere used: (1) a ramp loading history, in which the indentation load and displacement wererecorded; and (2) a step loading history, in which the indentation displacement was recorded as afunction of time. Analysis of the linearly viscoelastic material response was performed to measurethe creep compliance functions for the two materials under two different loading histories. The limitof linearly viscoelastic behavior for each of the two materials was determined through theobservation of the indent impression recovery after complete unloading; it is postulated that linearityis achieved if indentation impression is fully recovered after unloading. Results fromnanoindentation tests generally agree well with data from conventional tension and shear tests. It hasthus validated the techniques of measuring linear creep compliance in the glassy state usingnanoindentation with the Berkovich and spherical indenter tips.read more
Citations
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Journal ArticleDOI
Nanoindentation of biological materials
TL;DR: This work has shown that indentation data analysis can be used to investigate variations in mechanical properties with changes in tissue organization or composition in mineralized and soft tissues, and map mechanical properties spatially in complex biomaterials.
Journal ArticleDOI
Rheological measurements of the thermoviscoelastic response of ultrathin polymer films.
TL;DR: Results from use of a previously unknown method for characterizing the rheological response of nanometer-thick polymer films show that the material exhibits previously unobserved stiffening in the rubbery response regime.
Journal ArticleDOI
Spherical indentation of soft matter beyond the Hertzian regime: numerical and experimental validation of hyperelastic models
TL;DR: Although this finding supports the generally accepted view that many soft materials can be assumed to be linear elastic at small deformations, the nonlinear models facilitate analysis of intrinsically nonlinear tissues and large-strain indentation behavior.
Journal ArticleDOI
Contact creep compliance of viscoelastic materials via nanoindentation
TL;DR: In this article, the authors outline the evolution of contact creep compliance analysis and application for both conical and spherical indenter geometries, and show that the assumption of linear viscoelasticity is not maintained for any of these polymers when creep compliance is measured via conical indentation at the nanoscale, regardless of the rate of stress application.
Journal ArticleDOI
Viscoelastic characterization of polymers using instrumented indentation. I. Quasi-static testing
TL;DR: The use of instrumented indentation to characterize the mechanical response of polymeric materials was studied in this article, where a model based on contact between a rigid probe and a linear viscoelastic material was used to calculate values for the creep compliance and stress relaxation modulus for two glassy polymeric material, epoxy and poly(methyl methacrylate), and two poly(dimethyl siloxane) (PDMS) elastomers.
References
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Journal ArticleDOI
An improved technique for determining hardness and elastic modulus using load and displacement sensing indentation experiments
Warren C. Oliver,George M. Pharr +1 more
TL;DR: In this paper, the authors used a Berkovich indenter to determine hardness and elastic modulus from indentation load-displacement data, and showed that the curve of the curve is not linear, even in the initial stages of the unloading process.
Journal ArticleDOI
The relation between load and penetration in the axisymmetric Boussinesq problem for a punch of arbitrary profile
TL;DR: In this article, a solution of the axisymmetric Boussinesq problem is derived from which are deduced simple formulae for the depth of penetration of the tip of a punch of arbitrary profile and for the total load which must be applied to the punch to achieve this penetration.
Journal ArticleDOI
Indentation size effects in crystalline materials: A law for strain gradient plasticity
William D. Nix,Huajian Gao +1 more
TL;DR: In this article, the indentation size effect for crystalline materials can be accurately modeled using the concept of geometrically necessary dislocations, which leads to the following characteristic form for the depth dependence of the hardness: H H 0 1+ h ∗ h where H is the hardness for a given depth of indentation, h, H 0 is a characteristic length that depends on the shape of the indenter, the shear modulus and H 0.
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On the generality of the relationship among contact stiffness, contact area, and elastic modulus during indentation
TL;DR: In this paper, Sneddon's analysis for the elastic contact between a rigid, axisymmetric punch and an elastic half space is used to show that a simple relationship exists between the contact stiffness, the contact area, and the elastic modulus that is not dependent on the geometry of the punch.
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Hardness measurement at penetration depths as small as 20 nm
TL;DR: In this paper, the authors investigated the properties of indentation hardness on the sub-micrometre scale in nickel, gold and silicon and showed that indent areas and therefore hardness can be determined from penetration depth with reasonable accuracy, and that elastic relaxation can be quantitatively understood.
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