Connecting bond switching to fracture toughness of calcium aluminosilicate glasses

TL;DR

This study links bond switching in calcium aluminosilicate glasses to their fracture toughness, revealing how local atomic coordination changes influence mechanical resilience and highlighting the complexity of structure-property relationships.

Contribution

It provides the first detailed correlation between bond switching and fracture toughness in calcium aluminosilicate glasses using experimental and simulation methods.

Findings

Bond switching correlates positively with fracture toughness.

Structural factors beyond bond switching influence mechanical properties.

Variation in fracture toughness depends on local atomic coordination changes.

Abstract

Fracture toughness is a critical mechanical property of glasses, but a detailed understanding of its link to composition and structure is still missing. Here, focusing on the industrially important family of calcium aluminosilicate glasses, we measure the fracture toughness of two glass series using the single-edge precracked beam method, one based on tectosilicate compositions with varying silica contents and the other covering both percalcic and peraluminous compositions with varying Al/Ca ratio. To elucidate the structural origins of the variation in fracture toughness, we perform X-ray total scattering measurements and molecular dynamics simulations. Our findings show that local coordination changes of especially Al atoms, so-called bond switching, feature an overall positive correlation with fracture toughness. We also compare this variation with that in other mechanical properties, including elastic moduli, hardness, and crack initiation resistance. We find that various structural aspects need to be considered to describe and understand the mechanical properties of calcium aluminosilicate glasses.