Oral Reference: ICF100267OR IN-SITU CHARACTERIZATION OF MATRIX RESPONSE TO FIBER FRACTURES Jay C. Hanan1, Irene J. Beyerlein 2, Ersan Üstündag1, Geoffrey A. Swift1 Bjørn Clausen1, Donald W. Brown2, and Mark A. M. Bourke2 1 Department of Materials Science, California Institute of Technology, Pasadena, CA 91125, USA 2 Materials Science and Technology Division, Los Alamos National Laboratory, Los Alamos, NM 87545, USA ABSTRACT Successful application of metal matrix composites often requires strength and lifetime predictions that account for the deformation of each constituent. However, the deformation of individual phases in composites usually differs significantly from their respective monolithic behaviors. For instance, generally little is known about the in-situ deformation of the metal matrix and fiber/matrix interface region, other than that it likely differs from the bulk material response. This article describes an approach to quantifying the in-situ deformation parameters using neutron diffraction measurements of matrix failure around a fiber fracture in a model composite consisting of an Al matrix and a single Al2O3 fiber. We also study the shear sliding resistance as it evolves through fiber fracture upon loading and unloading. Matching the stress/strain distributions predicted from micromechanical models to the measured strain distributions determined by neutron diffraction under applied tensile loading results in an estimate of the typically non-linear, stress-strain behavior of the metal matrix. KEYWORDS Metal-matrix composite, neutron diffraction, constitutive behavior, fiber fracture, matrix yielding, AlAl2O3 composite, interface shear strength. INTRODUCTION The strength and lifetime of fiber composites are largely governed by the nucleation and interaction of fiber fractures. These fractures unload onto neighboring fibers and matrix, generating strain concentrations which can promote more fiber breaks. The magnitudes and length scales of the strain concentration fields depend on the response of the matrix and interface. Therefore, knowledge on the in-situ constitutive behavior of these regions are crucial for determining internal stress states. Particularly for metal matrix composites (MMCs), the deformation of the matrix material in-situ often differs significantly from its respective monolithic, bulk behavior. Generally little is known about the in-situ deformation behavior of the metal matrix and fiber/matrix interface region, other than that it likely differs from the bulk material response. There are many possible reasons: (i) microstructural constraints, (ii) localized strain gradients (e.g., near phase boundaries and defects), and (iii)
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