Fracture Analysis of a Laminated Window Structure

The glass layer on a number of laminated glass/polymer window structures experienced in-service fractures for no obvious reason. A fracture analysis was performed on one of these windows in an attempt to determine the fracture initiation site, fracture origin, estimated stress at fracture, and the fracture process. The analysis revealed that glass layers were scratched, most likely by the action of the wiper blades pulling/pushing debris across the glass. Cracking started due to damage from one of the scratches, and the crack pattern indicates that crack propagation was thermally driven due to the diurnal weathering environment. Fracture mechanics was used to estimate the stress at fracture, which was in excellent agreement with values reported for the glass that was scratched and then loaded in tension under controlled laboratory conditions.