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Title Why should the "alternative" method of estimating local interfacial shear Strength in a pull-out test be preferred to other methods?
Date 28.11.2018
Number 56171
Abstract One of the most popular micromechanical techniques of determining the local interfacial shear strength (local IFSS, td) between a fiber and a matrix is the single fiber pull-out test. The td values are calculated from the characteristic forces determined from the experimental force–displacement curves using a model which relates their values to local interfacial strength parameters. Traditionally, the local IFSS is estimated from the debond force, Fd, which corresponds to the crack initiation and manifests itself by a “kink” in the force–displacement curve. However, for some specimens the kink point is hardly discernible, and the “alternative” method based on the post-debonding force, Fb, and the maximum force reached in the test, Fmax, has been proposed. Since the experimental force–displacement curve includes three characteristic points in which the relationship between the current values of the applied load and the crack length is reliably established, and, at the same time, it is fully determined by only two interfacial parameters, td and the interfacial frictional stress, tf, several methods for the determination of td and tf can be proposed. In this paper, we analyzed several theoretical and experimental force–displacement curves for different fiber-reinforced materials (thermoset, thermoplastic and concrete) and compared all seven possible methods of td and tf calculation. It was shown that the “alternative” method was the most accurate and reliable one, while the traditional approach often yielded the worst results. Therefore, we proposed that the “alternative” method should be preferred for the experimental force–displacement curves analysis.
Publisher Materials (Open Access)
Identifier
Citation Materials (Open Access) 11 (2018) ID2406
DOI https://doi.org/10.3390/ma11122406
Authors Zhandarov, S. ; Mäder, E. ; Gohs, U.
Tags pull-out test local interfacial shear strength interfacial frictional stress analysis of force–displacement curves debond force “alternative” method

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