9/5/2023 0 Comments Fracture glass pictures cost![]() The term ‘yield stress’ therefore refers to the stress at which a significant change in slope of the stress–strain diagram is observed, rather than the onset of true plasticity. Although this is also adopted in this paper, these terms only refer to the shape of the stress–strain diagram, as the response remains viscoelastic in practice. This often leads to the misleading terminology of ‘elastic and ‘plastic’ when referring to the response of the PVB. 2014).Īn enhanced PVB stiffness is observed at high strain-rates, and the shape of the stress–strain diagram resembles an elastic–plastic material (Kott and Vogel 2003 Bennison et al. It should be noted that this applies for glass fragments that are unconfined, as the contribution of the fractured glass is non-negligible, even at very low strain rates, if confined between layers of unfractured glass (Overend et al. low strain rates), compared to the capacity of the intact panel (Kott and Vogel 2003, 2004, 2007), the response is fundamentally different at the high strain-rates associated with blast loading, due to the viscoelastic nature of PVB. Although this bending capacity has been experimentally demonstrated to be negligible under quasi-static loads (i.e. 2016).Īn additional benefit of the glass-PVB bond is that the attached glass fragments contribute to the post-fracture capacity of the panel, resulting in a composite bending action that involves the interlayer, working in tension, together with the glass fragments that come into contact as the panel deforms, working in compression. Furthermore, some fragments invariably delaminate at large deflections (Hooper 2011 Pelfrene et al. ![]() This bond is not a universal constant and is affected by environmental factors (Butchart and Overend 2012, 2013, 2017 Samieian et al. Following the fracture of the glass layers, it is this bond that retains the glass fragments on the interlayer, thereby reducing the risk of glass-related injuries during blast events. The lamination of the glass layers and PVB results in a strong adhesion bond forming between the glass layers and the PVB. The focus here is on the former, as this is the most common interlayer used in building façades. ![]() Although many interlayer types are available, the UK Centre for the Protection of National Infrastructure recommends using only Polyvinyl butyral (PVB) and ionomer interlayers for blast protection (CPNI 2019). These composite sandwich panels, consisting of multiple glass layers laminated with a transparent polymer interlayer, hold the glass fragments in place and offer enhanced capacity by providing resistance to the blast wave after the glass layers have fractured. Resilient glazed façades, capable of offering such protection, can be achieved by using ductile, laminated glass panels instead of inherently brittle, monolithic glass panels. 1 Introductionĭuring a blast event, the façades of buildings act as the first barrier of defence in protecting occupants, by preventing the blast waves from penetrating the interior. This suggests that the idealised pattern with aligned cracks, considered in previous work, results in a lower-bound estimate of the bending capacity for panels with random fracture patterns formed under blast loading. ![]() An enhancement of the bending capacity is consistently observed for specimens with misaligned cracks that is almost twice that of specimens with aligned cracks. The results demonstrate that the bending moment capacity of the specimens is unaffected by the number and size of the glass fragments, and by the choice of the loading rig. This paper addresses these concerns by reporting on further low-temperature tests that have considered four additional pre-fractured patterns in both three- and four-point bending. Under blast loads, however, a random pattern of irregular fragment sizes occurs, with the cracks not always aligned in the two glass layers.Īdditionally, the plastic hinge location within each specimen coincided with the point of application of the load, which may have influenced the results. These tests were performed on specimens with an idealised fracture pattern, by pre-fracturing cracks at a uniform spacing of 20 mm, aligned in both glass layers. Three-point bending tests performed previously on laminated glass specimens at low temperature, which aimed to simulate the effects of high strain-rate due to the time-temperature dependency of the interlayer, demonstrated an enhancement of the ultimate load capacity by two orders of magnitude compared to that at room temperature. These ductile panels offer residual bending resistance following the fracture of the glass layers, due to the composite action of the attached glass fragments in compression and the interlayer in tension. Laminated glass panels are increasingly installed in glazed façades to enhance the blast protection of buildings. Source: Glass Structures & Engineering, volume 7 ![]()
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