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Residual Stresses and Resulting Damage Within Fibers Intersecting A Free Surface

Published online by Cambridge University Press:  15 February 2011

J. M. Galbraith ,
M. N. Kallas ,
D. A. Koss  and
J. R. Hellmann
J. M. Galbraith
Affiliation:
Center for Advanced Materials, The Pennsylvania State University, University Park, PA 16802
M. N. Kallas
Affiliation:
Center for Advanced Materials, The Pennsylvania State University, University Park, PA 16802
D. A. Koss
Affiliation:
Center for Advanced Materials, The Pennsylvania State University, University Park, PA 16802
J. R. Hellmann
Affiliation:
Center for Advanced Materials, The Pennsylvania State University, University Park, PA 16802
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Abstract

Finite element as well as indentation fracture mechanics modeling have been used to analyze the evolution of fiber damage that was observed at the ends of fibers intersecting a free surface in sapphire-reinforced TiAl matrix composites. Experimental observations indicate that, under certain conditions, surface cracks introduced during cutting will propagate along the fiber axis due to thermally-induced residual stresses. Finite element computations predict that significant thermally-induced residual tensile stresses exist near the ends of sapphire fibers which are embedded within TiAl-based matrices and are oriented normal to a free surface. Crack growth behavior induced by microhardness indentations is used to experimentally verify the FEM predictions. The results indicate that a biaxial tensile residual stress state exists near the fiber ends due to a thermal expansion mismatch. The magnitude of the residual stresses are a sensitive function of interfacial bond strength and elastic/plastic properties of the interfacial region and may be sufficient to propagate pre-existing cracks.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 273: Symposium Q – Intermetallic Matrix Composites II , 1992 , 119
Copyright
Copyright © Materials Research Society 1992

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References

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