Pre- and Post-Failure Experimental Bending Analysis of Glass Elements Coated by Aged Anti-Shatter Safety Films

Abstract

The main goal of Anti-Shatter Films (ASFs) applications for structural glass is to create a barrier able to keep together fragments and minimize risk after any impulsive or static load that could lead glass to cracking. The influence of ASF properties on the flexural strength of coated glass elements is thus a relevant topic for safe design purposes, but still little investigated. To this aim, an experimental material investigation is presented in this paper, in order to achieve a good knowledge of common ASFs from a chemical point of view. Moreover, the deterioration of mechanical and adhesion characteristics for ASF samples subjected to different environmental conditions and accelerated ageing is also investigated, so as to simulate the effects of long-term exposure to high humidity (HU) or high temperature (HT). An experimental campaign carried out on 20 small scale ASF-coated glass specimens is finally presented, based on a three-point bending (3PB) test setup. The out-of-plane bending response of unaged or aged samples is performed by taking into account two different displacement-rate levels, to assess their performance and bending capacity under steady-static or impulsive loads. In both cases, the attention is given to the characterization of elastic and post-failure performances. Finally, support for the interpretation of experimental outcomes is derived from a simplified theoretical model of composite beam with partial connection, in order to estimate the shear stiffness of ASF adhesive components in the elastic stage.

Post-Fracture Stiffness and Residual Capacity Assessment of Film-Retrofitted Monolithic Glass Elements by Frequency Change

“…Assuming that the bonding film has minimum bending stiffness (with 0.35 mm its thickness [18][19][20], M f = 0.3969 g ≈ 0 and E f = 8.1 MPa), f 1 in Equation ( 1) mostly depends on the Young's modulus E = 70 GPa of glass, on the second moment of area J of the uncracked B × t glass section, and on the corresponding bending stiffness EJ. To note that the analytical results from Equation (1) represent an ideal upper limit for the tested cantilever samples, which in real constructions may be generally affected by the possible support flexibility (if any) or degradation (if any), delamination (in case of laminated sections), glass fracture (as in the present analysis), etc., with major effects on the final dynamic performances [22,38].…”

“…In terms of structural safety, anti-shatter films can support the post-fracture stage, as they can prevent the spread of critical shards from cracked monolithic glass components (Figure 1 and study by Figuli et al [15]). Given that these films are typically used for post-fracture hazard minimization, but are characterized by the small thickness, very limited bending stiffness, and uncertain adhesion properties, an open question is represented by the quantification of their mechanical potential in keeping glass fragments together, especially under aging or unfavorable conditions [18][19][20]. Among others, debonding and fall-out of glass shards [21,22] would in fact result in major consequences for glass section, and thus for the customers.…”

“…Following the above considerations, the present investigation focuses on the dynamic characterization of small-scale samples consisting of a fractured monolithic glass plate with fragments bonded by antishatter film. To verify the proposed experimental strategy, a commercial safety film based on polyethylene terephthalate (PET)-layers and pressure sensitive adhesives (PSAs) is taken into account, with mechanical and thermo-physical properties as in [18][19][20]. By taking an advantage of previous experimental efforts at the material characterization level [18][19][20], the primary goal of current investigation is represented by the experimental characterization of cracked glass-film composite samples in cantilever setup and subjected to the random repeated vibrations.…”

“…To verify the proposed experimental strategy, a commercial safety film based on polyethylene terephthalate (PET)-layers and pressure sensitive adhesives (PSAs) is taken into account, with mechanical and thermo-physical properties as in [18][19][20]. By taking an advantage of previous experimental efforts at the material characterization level [18][19][20], the primary goal of current investigation is represented by the experimental characterization of cracked glass-film composite samples in cantilever setup and subjected to the random repeated vibrations. Based on vibration frequency analysis, their residual post-fracture stiffness and mechanical capacity is tracked and measured.…”

Mitigating Blast Hazards: Experimental Evaluation of Anti-Shatter Films and Catcher-Cable Systems on Conventional Windows

“…Further information on the characteristics of ASFs for blast protection can be found in [7,8]. It should be noted that the durability of ASFs has not yet been conclusively assessed [9]. Often a warranty of about 10 years is given.…”