Characterization of fiber-composite interphase properties
Abstract
Atomic Force Microsopy (AFM) and finite element method (FEM) are used to perform characterization of stiffness properties near the fiber-matrix interface. Characterization performed in this study is more representative of the sample surface than past studies because all the matrix points on the sample surface are analyzed as opposed to smaller sets of data such as points along a single line or linear profiles that is the common practice. Using the AFM force modulation mode, stiffness characterization for an in situ sample is performed in the radial direction and angular direction. It is shown that final results vary based on the postprocessing method used. The difference in results for the same data are attributed to inherent asymmetry in the stiffness around the fiber and the method used in this analysis to distinguish the fiber and matrix phases on the sample surface. Low magnification AFM results are compared with FEM simulations which model the indenter as flat surfaces. FEM simulations with fibers in hexagonal and square array arrangements are shown to be in good agreement with experimental results using radial stiffness characterization. Furthermore, finite element frictionless contact model using a spherical shaped indenter simulates material response as the indenter probe is moved closer to the fiber boundary. It is shown that the normalized stiffness results predicted with contact model are consistent with previous experimental results which show that the boundary effect varies for different indentation loads. Finally, after processing high resolution AFM data it will be possible to compare the results with localized stiffness response predicted by contact simulations.
Degree
M.S.M.E.
Advisors
Koslowski, Purdue University.
Subject Area
Mechanical engineering|Materials science
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