| Summary: | Particulate metal matrix composites (MMCs) offer a number of property incentives over metallic
alloys. However, their applicability as engineering materials is limited by their low ductility.
Experimentally, the MMC ductility has been observed to be affected by the spatial distribution of
the reinforcements, particularly by the presence of regions of high reinforcement density or
clusters. The goal of the present work was to develop a predictive understanding of the effect of
reinforcement distribution on the MMC failure mechanism, through a combination of numerical
simulations and model experiments. Numerical models (including finite element models) were
constructed to study the effect of distribution (both random and clustered) on the reinforcement
stress in undamaged and damaged composites. The models were verified by experimental
measurement of the reinforcement stress and the composite stress in AA6O6I - AI₂O₃ and Cu-W
composites. The models showed that proximity of the reinforcements along the line of loading
may enhance reinforcement stress in an undamaged composite, and cause premature damage
nucleation. On the other hand, proximity to a damaged reinforcement along a direction
perpendicular to the line of loading was observed to enhance the stress in the neighboring
particles, and may lead to their failure. Thus, the overall MMC failure mechanism may be
affected by reinforcement proximity in all directions. A suitable parameter proposed for
characterizing such dependence is the local reinforcement area-fraction. The local area-fraction
maps were constructed for various computer generated microstructures, using a Voronoi
tessellation algorithm. The maps were able to distinguish between the various patterns, and
determine important cluster characteristics, like the cluster shape, size and position. These maps
are expected to aid microstructure-property correlation in MMCs, and develop an 'intelligent'
framework for microstructural engineering of these materials for ductility enhancement. === Applied Science, Faculty of === Materials Engineering, Department of === Graduate
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