A homogenized model for the post-breakage tensile behavior of laminated glass

Laminated glass, a composite made by bonding glass plies with polymeric interlayers, can maintain a significant load bearing capacity even when glass is broken, because of the adhesion of the glass shards to the interlayer. The post-breakage response is strongly associated with the safety performance, but it is not as well studied as the pre-glass breakage stage. Here, the tension stiffening of the interlayer due to the adhesive contact with the shards is considered as a stress perturbation, determined though a variational approach by minimizing the complementary energy functional. This allows to reach a simple but accurate estimate of the effective stiffness of the cracked laminate, which results to be strongly dependent, besides the interlayer elastic properties, upon the fragment size and the glass-to-polymer adhesion. An energetic competition à la Griffith determines the expected load vs. displacement response in a tensile test. Comparisons with numerical experiments confirm the good accuracy of the proposed approach.