Abstract
Anti-shatter safety films (ASFs) are often used for structural glass applications. The goal is to improve the response of monolithic elements and prevent fragments from shattering. Thus, the main reason behind their use is the possibility to upgrade safety levels against the brittle failure of glass and minimize the number of possible injuries. However, the impact response of glass elements bonded with Polyethylene terephthalate (PET)-films and pressure sensitive adhesives (PSAs) still represents a research topic of open discussion. Major challenges derive from material characterization and asymmetrical variability under design loads and ageing. In particular, the measurement of interface mechanical characteristics for the adhesive layer in contact with glass is a primary parameter for the ASF choice optimization. For this reason, the present paper presents an experimental campaign aimed at calibrating some basic mechanical parameters that provide the characterization of constitutive models, such as tensile properties (yielding stress and Young modulus) for PET-film and adhesive properties for PSA (energy fracture and peel force). In doing so, both tensile tests for PET-films and peeling specimens are taken into account for a commercially available ASF, given that the peeling test protocol is one of most common methods for the definition of adhesion properties. Moreover, an extensive calibration of the Finite Element (FE) model is performed in order to conduct a parametric numerical analysis of ASF bonded glass solutions. Furthermore, a Kinloch approach typically used to determine the fracture energy of a given tape by considering a variable peel angle, is also adopted to compare the outcomes of calibration analyses and FE investigations on the tested specimens. Finally, a study of the effect of multiple aspects is also presented. The results of the experimental program and the following considerations confirm the rate dependence and ageing dependence in peel tests.
Highlights
Background of Peeling Mechanics and CurrentApproachAdhesion is an extremely complex process that concerns the creation and toughness of the bonding that can take place between any two materials
To obtain a consistent value of adhesion energy, which can be successively calibrated through Finite Element (FE) numerical procedures, a mean of the peel angle is considered in order to apply the equations proposed in [25], based on the elastic-plastic behaviour of the peeling arm modelled as a bilinear, work-hardening material (E2 = αE)
The mechanical behaviour of unaged and aged multi-layer anti-shatter films (ASFs) for safety covers in structural glass applications was investigated based on experimental methods, theoretical approaches and Finite Element (FE) numerical modelling techniques
Summary
Adhesion is an extremely complex process that concerns the creation and toughness of the bonding that can take place between any two materials. Adhesive properties are measured by peel testing, and the approach is suitable, especially when considering weak adhesion, as the deformation in the peel arm can be accounted for as elastic. There are no quantities in Equation (2) which can be attributed to the mechanical properties of the material, adhesive, or to the thickness of the strip This limit depends on the simplified hypothesis of perfectly rigid in tension and completely flexible in bending tape, and the external work is transferred to the surface at the separation point. To obtain a consistent value of adhesion energy, which can be successively calibrated through FE numerical procedures, a mean of the peel angle is considered in order to apply the equations proposed in [25], based on the elastic-plastic behaviour of the peeling arm modelled as a bilinear, work-hardening material (E2 = αE). It is worth noting the rather close correlation of calculated values, namely in the form of a rather small percentage variation in the proposed comparative charts
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