To develop a deeper understanding of how cracks grow in brittle materials this research examines the role of microstructural constituents in affecting crack instability. Fracture toughness, crack velocity, and high strain rate measurements are combined with systematic variations in the size, shape and distribution of microstructural constituents. Model materials and commercial materials are employed in the study with emphasis on metal-matrix materials with a controlled size distribution of brittle, second- phase precipitates or dispersoids. A predictive model for fracture toughness as a function of particle strength, size and distribution should result.
