EFFECT OF NONBRIDGING OXYGENS ON THE FRACTURE-TOUGHNESS OF SYNTHESIZED GLASSES

Plane strain indentation fracture toughness and Young's modulus measurements were used to compare the mechanical properties with the chemical compositions of potassium soda silicate and feldspathic glasses synthesized by wet-chemical methods. The concentration of nonbridging oxygens within these glasses was calculated from their chemical composition as determined by atomic absorption spectrophotometry (AAS) [6-8]. Regression analyses indicated that there is a significant correlation between the dynamic Young's modulus and fracture toughness when plotted against the concentration of nonbridging oxygens. Student-Newman-Keuls (SNK) analyses of nonbridging oxygens, dynamic Young's modulus and fracture toughness were able to rank and separate these glasses into several groups at the 0.99 and 0.95 levels of confidence.