Strength and Fracture Toughness of Binary Alkali Silicate Glasses.

摘要

The strength, modulus of elasticity, fracture surface energy, and their relationship were investigated for a series of alkali silicate glasses ranging in composition from R2O.2SiO2 to R2O.5SiO2, where R2O was either Li2O, Na2O or K2O. Measurements were also made on commercial fused silica. The strengths and fracture surface energies decreased with increasing silica content in all three systems, even though the moduli of elasticity exhibited different trends. In all cases, the strengths varied in an approximately linear manner with the fracture toughness, or (square root of 2E gamma Sub f). No quantitative relationship between the fracture surface energies and the amounts off flow as measured by the microhardness was found to exist. Further, the fracture surface energies were not related to the elastic moduli. Flaw sizes calculated for the annealed Na2O-SiO2 glasses were shown to be related to the sizes of the separated microphase observed by transmission electron microscopy as predicted by Watanabe and Moriya. The flaw sizes for the abraded alkali silicate glasses were shown to be inversely related to the fracture surface energies. Finally, the consistency obtained when calculating the flaw sizes indicates that the strength of glasses is adequately described by a Griffith-Orowan type equation. (Author)