Effects of experimental variables on PMMA nano-indentation measurements

Jin, Tao; Niu, Xiaoyan; Xiao, Gesheng; Wang, Zhi Hua; Zhou, Zhiwei; Gao, Yuan; Shu, Xuefeng

doi:10.1016/j.polymertesting.2014.09.015

Cited by 53 publications

(22 citation statements)

References 16 publications

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“…Moreover, by comparing with the slopes of the creep curves, it can be seen that the creep rates decrease gradually over holding time, and are easier to reach a steady state under the lower peak load within the same period. According to the creep curves, indentation creep rates

\overset{ɛ}{true}

can be calculated by

\dot{ɛ} = d h / (h d t)

, where

h

and t are the instantaneous indentation depth and time . The reason for this phenomenon may be due to the relaxation time

τ

decreasing with the increasing peak load which has been confirmed by Panayiotis Georgiopoulos et al .…”

Section: Resultsmentioning

confidence: 69%

“…The reduced modulus and hardness remain relatively stable after a 200 s holding period. The reason may be that the creep effect is dominant during the initial stage, and then a longer holding time will exhaust the influence upon the unloading process, providing enough relaxation of membrane and therefore the system can reach a mechanical equilibrium before the subsequent unloading . Moreover, the reduction of modulus and hardness can be partially considered as the result of increased contact area due to the penetration depth growth.…”

Section: Resultsmentioning

confidence: 80%

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Effects of loading conditions on the nanoindentation creep behavior of nafion 117 membranes

Xia

Zhou

Zhang

et al. 2018

Polymer Engineering & Sci

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In this work, nanoindentation tests on Nafion 117 membranes are conducted under three different sets of loading conditions. The effects of loading/unloading rate, peak load and holding period on the mechanical responses of membranes are analyzed, respectively. The results demonstrate that the creep deformation as well as the modulus and hardness depend on these loading conditions, and appropriately fast loading/unloading rate, long enough holding time, relatively low peak load are essential to minimize the creep effect on the nanoindentation results. By analyzing the variation tendency of reduced modulus and hardness, the optimized loading/unloading rate, holding time and the peak load are >10 μN/s, longer than 20 s and 100 μN for dry Nafion 117. POLYM. ENG. SCI., 58:2071–2077, 2018. © 2018 Society of Plastics Engineers

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\overset{ɛ}{true}

can be calculated by

\dot{ɛ} = d h / (h d t)

, where

h

and t are the instantaneous indentation depth and time . The reason for this phenomenon may be due to the relaxation time

τ

decreasing with the increasing peak load which has been confirmed by Panayiotis Georgiopoulos et al .…”

Section: Resultsmentioning

confidence: 69%

Section: Resultsmentioning

confidence: 80%

Effects of loading conditions on the nanoindentation creep behavior of nafion 117 membranes

Xia

Zhou

Zhang

et al. 2018

Polymer Engineering & Sci

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show abstract

“…Indentation has been successfully applied to several polymers, such as poly(methyl methacrylate) [10], and polymer systems [11][12][13][14][15][16][17][18][19][20], such as blends [21], copolymers [22,23], composites [24,25], bone cement [26], and multilayer systems [27]. However, its applicability is strictly limited by the probe dimension that allows spatial resolution of the order of tens of microns and does not allow the reconstruction of an accurate mapping of the sample surface.…”

Section: Introductionmentioning

confidence: 99%

Micromechanical Characterization of Complex Polypropylene Morphologies by HarmoniX AFM

Liparoti

Sorrentino

Speranza

2017

International Journal of Polymer Science

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This paper examines the capability of the HarmoniX Atomic Force Microscopy (AFM) technique to draw accurate and reliable micromechanical characterization of complex polymer morphologies generally found in conventional thermoplastic polymers. To that purpose, injection molded polypropylene samples, containing representative morphologies, have been characterized by HarmoniX AFM. Mapping and distributions of mechanical properties of the samples surface are determined and analyzed. Effects of sample preparation and test conditions are also analyzed. Finally, the AFM determination of surface elastic moduli has been compared with that obtained by indentation tests, finding good agreement among the results.

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“…Indentation testing has been widely applied to characterize and determine properties of materials at nano-to micrometer length scales [1][2][3][4][5][6][7][8][9][10][11][12]. The deformation mechanisms and behavior at these length scales can be significantly different compared to those at the macroscopic length scale, and nanoindentation testing has been a vital tool to unravel these differences.…”

Section: Introductionmentioning

confidence: 99%

Length scale effects in epoxy: The dependence of elastic moduli measurements on spherical indenter tip radius

Chandrashekar

Han

2016

Polymer Testing

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Significant increases in the measured elastic moduli with decreasing indentation depth have been previously found in various polymers by indentation tests with a Berkovich tip at micro-to nanometer length scales. These increases in the determined elastic moduli were related to second order displacement gradients which increase with decreasing depth when a conical tip is applied.When a spherical tip is applied, such depth dependence should not be present as the second order displacement gradients remain essentially unchanged with indentation depth. However, these gradients should be proportional to the radius of the spherical tip. To examine the notion of second order displacement gradient dependence in measurements of elastic moduli, indentation experiments are conducted on epoxy with spherical tips of different nominal radii. Accounting for tip imperfections, an increase in the determined elastic moduli is found with decreasing tip radius, which corroborates the notion of second order displacement gradient dependence. 250 µm nominal radii. To address tip imperfections, the tips are examined with fused silica as a reference material. The results of these experiments are discussed in view of other possible factors and interpretations. Experiments Sample preparationEpoxy samples were prepared by mixing the commercially available liquid epoxy resin, EPON 828 (bisphenol A-epichlorohydrin), as base agent with the curing agent EPIKURE 3223, diethylenetriamine (DETA). The epoxy resin (Momentive Specialty Chemicals, USA) and DETA (Momentive Specialty Chemicals, USA) were used in the sample preparation following a procedure identical to that followed in [10], except that a curing agent content of 9 phr (parts per hundred resin) was used in the sample preparation, as opposed to 20 phr. Indentation testingThe indentation experiments were conducted at room temperature of about 23 o C with spherical tips of 3, 10, 50 and 250 µm nominal radii on an Agilent G200 nanoindenter system equipped with XP and DCM heads. The 3, 10 and 50 µm radii tips were purchased from SYNTON-MDP AG (Nidau, Switzerland) and the 250 µm tip was purchased from Micro Star Tech (Huntsville, TX, USA). The 3 µm radius tip was mounted on the DCM head and the other three tips on the XP head. The XP and DCM heads have load limits of 500 mN and 30 mN, respectively, which correspondingly limit the maximum indentation depth. The indentation experiments were conducted in two stages: 1) Tip imperfection study using fused silica as the reference material.2) Determination of elastic moduli of the epoxy sample.

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Effects of experimental variables on PMMA nano-indentation measurements

Cited by 53 publications

References 16 publications

Effects of loading conditions on the nanoindentation creep behavior of nafion 117 membranes

Effects of loading conditions on the nanoindentation creep behavior of nafion 117 membranes

Micromechanical Characterization of Complex Polypropylene Morphologies by HarmoniX AFM

Length scale effects in epoxy: The dependence of elastic moduli measurements on spherical indenter tip radius

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