The mechanical characteristics of fractured thermally prestressed glass

Thermally prestressed soda–lime–silica glass (TPG), also referred to as tempered or fully toughened glass, is widely used in monolithic and laminated glazing elements subjected to high wind loads, impact, and thermal shock, where high fracture resistance at the ultimate limit state is required. Although the load-bearing capacity of TPG up to fracture is well understood, reliable prediction of its post-fracture strength and stability remains challenging and is often based on costly full-scale prototype testing. The difficulty arises because fracture fundamentally alters the bulk mechanical characteristics of glass elements, and these key properties have not yet been systematically quantified.This study experimentally quantifies three key mechanical characteristics governing the post-fracture response of TPG, supported by complementary theoretical and numerical analyses: (i) the in-plane strain released upon fracture, (ii) the effective elastic modulus of fractured glass, and (iii) the shear strength of fractured thermally prestressed glass. The in-plane strain release measured in this study, exceeded recent model predictions by 34% to 98%, indicating limitations in current predictive approaches and/or the experimental setup. The effective elastic modulus of fractured glass was found to be largely independent of thermal prestress level, with representative mean values of Efg = 4.00 GPa for 12 mm thermally prestressed glass and Efg = 2.89 GPa for 19 mm thermally prestressed glass. In addition, the mean shear strength of the fractured glass assembly remained approximately constant at 10 MPa and was not significantly affected by post-fracture in-plane compression. Finally, the applicability of the derived mechanical characteristics was demonstrated for two representative real-world glass configurations: one monolithic and one laminated. These findings establish a basis for improved, physically-representative, post-fracture design methodologies for thermally prestressed glazing systems, enabling reliable prediction of residual load bearing capacity and structural stability.