Failure Strengths of Laminated Glass

Laminated glass used in architectural glazing comprises two layers of glass connected by a thin interlayer of polyvinyl butyral. Previously reported nondestructive experimental stress analyses offer evidence that laminated glass behaves like monolithic glass of the same nominal thickness except when temperatures are high. This evidence has been augmented to include failure behavior by destructive tests of a large number of laminated‐glass specimens. Test results reveal that failure strengths of annealed laminated‐glass specimens are equal to failure strengths of annealed monolithic glass specimens of the same nominal thickness at room temperature, and decrease to about 75% of monolithic‐glass strength at 170° F (77° C). Further, heat strengthened and fully tempered laminated‐glass specimens exhibit failure strengths that are approximately three and five times, respectively, the strengths of annealed monolithic‐glass specimens of the same nominal thickness, suggesting monolithic behavior of these types of laminated glass, as well.