Laminated glass is used in many industries to provide safety and security to people. Laminated glass possesses many beneficial properties that enable the safety of passengers in both automobiles and airplanes.
In this article, we take a look at laminated glass and what benefits it can bring to automobiles, and those who travel in automobiles.
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What is Laminated Glass?
Laminated glass is a form of safety glass. In automobiles, laminated glass consists of two panes of glass separated by an interlayer of soft polymer. More panes, as seen in the safety glass within the aviation industry, would be too thick and heavy for automobiles. Laminated glass is often used as a replacement for windshields, as it possesses many properties that are not only beneficial for maintaining the structural integrity of the windshield, but they also aid in increasing passenger safety and security.
Where many standard windshields will crack then shatter, laminated glass (unless there are certain circumstances) will not shatter and remain intact. Instead, laminated glass produces a spider web crack pattern with locked-in fragments of glass.
Property Benefits of Laminated Glass
Laminated glass contains two panes of glass, compared to one in standard glass. This thickness automatically increases its strength because there is more material for a projectile, or energy transference from an impact, to penetrate through. Added to this, is the interlayer material. This means that there are 3 layers to penetrate. The interlayer is also very strong; and possesses a high tensile strength and good rigidity. The interlayer is also strong enough to support the entire load once the integrity of the glass has been compromised. In all, it takes a lot of force to break through a windshield of laminated glass compared to conventional single pane windshield glass.
Resistance to Shattering
In addition to its high strength, laminated glass also exhibits a high resistance to cracking. Once the lower pane starts to crack, the crack follows through to the second pane; but this is usually through a portion of the second pane. At this point, the interlayer polymer possesses a high enough tensile strength to support the load of the windshield. Additionally, the two glass panes, in conjunction with the interlayer material, ‘locks’ the broken glass fragments in place using compressional forces. This means that laminated glass does not shatter.
Laminated glass acts in a similar way to double glazing for sound reduction. Not only do sound waves have to pass through two panes of glass, they must also pass through the polymer interlayer material. Through all three materials, sound waves can become absorbed by the material, leading to a reduction in the external traffic noise heard while driving.
Laminated glass is also fire resistant. For applications outside of the automotive industry, the resistance can be increased further if the application requires, using special interlayer materials. Radiation resistance can also be introduced.
The interlayer polymer is usually a thermosetting polymer and is the main reason for the high thermal/fire resistance in laminated glass. This means that it forms 3D cross links within itself, and it sometimes forms cross-links with the surrounding material(s) (in this instance, the glass panes). This 3D network is highly resistant to temperature degradation, because it takes a lot of thermal energy to break the covalent bonds in the cross-link.
Societal Benefits of Laminated Glass
Due to the increased strength (and other properties) of the glass, the safety of the passengers traveling in the car is increased. If the car does happen to be involved in an accident and the energy of the crash affects the windshield, the passengers are much safer than in a single pane windshield.
The non-shattering ability of laminated glass not only prevents shards of glass from flying through the car towards the passengers upon impact, it also prevents anybody who is not wearing their seatbelt, from ejecting through the windshield and onto the road. Even if the fragments eventually fall from the windshield, they do not have the velocity and energy generated from the impact, therefore, they pose a much lower risk if they are merely dropping out from the windshield.
Laminated glass not only protects passengers from impacts, but also projectiles. Projectiles can come in many forms, from stone chips being thrown up from the road, from passing alongside a gritter, and even from people physically launching projectiles. The high strength and blast resistance to projectiles gives the passengers a much greater security. Instead of a hole in the glass and small shards of glass being released towards the passengers (as with conventional glass), the laminated glass is unlikely to be fully penetrated and therefore the glass shards released are minimal.
The high sound proofing ability of laminated glass means that the driver is less likely to be distracted by outside noises and therefore is less likely to crash from an external distraction – especially one that is audible in nature.
“Investigation of impact fracture behavior of automobile laminated glass by 3D discrete element method”- Zang M. Y., et al, Comput. Mech. 2007, DOI:10.1007/s00466-007-0170-1
“Blast and Impact Resistance of Laminated Glass Structures”- Hooper P., et al, Proceedings of the IMPLAST 2010 Conference, 2010
Lund University: http://www.byggmek.lth.se/fileadmin/byggnadsmekanik/publications/tvsm5000/web5198.pdf