Fracture Energy and Strength Behavior of a Sodium Borosilicate Glass‐Al2O3 Composite System

Publisher Website
Google Scholar
Abstract
Fracture energy and strength were determined for three series within a sodium borosilicate glass‐Al2O3 dispersed composite system. The average particle sizes of the Al2O3 dispersions were , and μm. Within each series, composites containing 0.10, 0.25, and 0.40 vol fractions of the Al2O3 dispersed phase were vacuum hot‐pressed. The fracture energy was determined at 77°K with the double cantilever specimen configuration. Strength was measured by a 4‐point flexural test. A significant increase in fracture energy was observed (up to 5 times the fracture energy of the glass without second‐phase dispersion). The fracture energy depended on the interparticle spacing and average particle size of the Al2O3 dispersion. These results could best be explained by a previously proposed model for the interaction of a crack front with a second‐phase dispersion. Surface roughness also contributed to the increased fracture energy. Some composites were strengthened significantly relative to the glass without a dispersion. Calculation of the crack size showed that the Al2O3 dispersion increased the crack size of the glass by ∼1 to 3 times the average particle size of the Al2O3 dispersion. Thus, the dispersion increased both the fracture energy and the crack size. These opposing parameters ultimately determined the strength behavior of these composites.