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Measurements of diffusion thickness at polymer interfaces by nanoindentation: A numerically calibrated experimental approach

  • Chunyu Yang (a1), Chieh-Tsung Lo (a2), Ashraf F. Bastawros (a1) and Balaji Narasimhan (a2)

Abstract

The interfacial fracture toughness and the adhesion strength of two dissimilar materials are governed by the diffusion interfacial thickness and its mechanical characteristics. A new testing methodology is implemented here to estimate the actual interfacial thickness from a series of nanoindentations across the interface, under the same applied load, with tip radius and indentation depth many times larger than the interface thickness. The bimaterial system used is a semicrystalline polymer interface of isotactic polypropylene and linear low-density polyethylene. The laminate is prepared under a range of diffusion temperature to yield diffusion interfaces of 0 to 50 nm. A numerical relationship is developed using two-dimensional (2D) finite element simulation to correlate the true interfacial thickness, measured by transmission electron microscopy, with the experimentally estimated apparent interfacial thickness, derived from the transition domain of a series of indents across the interface. A range of material-pairs property combinations are examined for Young’s modulus ratio E1/E2 = 1 to 3, yield strength ratio σY1Y2 = 1 to 2.5, and interfacial thickness of 0 to 100 nm. The proposed methodology and the numerically calibrated relationship are in good agreement with the true interfacial thickness.

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a) Address all correspondence to this author. e-mail: bastaw@iastate.edu

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Measurements of diffusion thickness at polymer interfaces by nanoindentation: A numerically calibrated experimental approach

  • Chunyu Yang (a1), Chieh-Tsung Lo (a2), Ashraf F. Bastawros (a1) and Balaji Narasimhan (a2)

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