Damage Assessment of Through-Cracked-Bending Laminated Glass Elements Under Low-Velocity Hard-Body Impacts

The post-fracture mechanical performance of laminated glass (LG) members is well-known to be challenging to assess due to the influence of multiple factors. Even more challenging and scarcely explored is the assessment of the behavior of broken LG elements as a function of the degree of damage that affects it. In this paper, the attention is given to the experimental analysis of 2-ply, small-scale, pre-fractured LG elements composed of annealed (AN) glass and characterized by two different types of interlayers, namely the polymeric Ethylene-Vinyl Acetate (EVA) or the ionoplast SentryGlas® (SG) bonds. The samples—with total size of 200 mm in length by 50 mm in width—are subjected to n = 10 repeated hard-body impact tests, in a three-point-bending (3PB) setup, to simulate and assess a possible increase in the damage severity. To quantify and compare the behavior of the different interlayers in use, experimental modal analyses are performed both at the beginning of the impact tests (n = 0) and after each hard-body impact repetition (n = 1, …, 10), by means of roving hammer tests based on #14 different control points. The comparison of the experimental outcomes—in particular, the fundamental vibration frequency f1—gives evidence of a markedly different mechanical response from the EVA and SG interlayers. EVA samples exhibited a major reduction in terms of fundamental frequency, indicating significant propagation of damage following impact repetitions. On the other hand, SG samples appear to be less seriously affected by hard-body impacts.