Subcritical crack growth behavior of Al2O3-glass dental composites

The purpose of this study is to investigate the subcrit. crack growth (SCG) behavior of alumina-glass dental composites. Alumina-glass composites were fabricated by infiltrating molten glass to porous alumina preforms. Rectangular bars of the composite were subject to dynamic loading in air, with stressing rates ranging from 0.01 MPa/s to 2 MPa/s. The SCG parameter n was detd. to be 22.1 for the composite, which is substantially lower than those of high-purity dense alumina. Investigations showed that glass phases are responsible for the low n value as cracks propagate preferentially within glass phases or along the interface between glass phases and alumina phases, due to the fact that glasses are more vulnerable to chem. attacks by water mols. under stress corrosion conditions. The SCG behavior of the infiltration glass was also investigated and the SCG parameter n was detd. to be 18.7