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Why are some OEMs using Laminated Sidelights, who's providing them and what is the trend?
OEMs use laminated sidelights as a safety and noise dampening feature. It is observed that among the OEM models that use laminated glass windows, the premium luxury car makers are more likely to provide them in all four side windows. A National Highway Traffic Safety Administration (NHTSA) study found that the risk of serious injury and death can be reduced considerably by providing safety glasses for the front windows of a car. This explains why many OEMs provide laminated glasses only for the two front doors (other than the windshield). As per the Ejection Mitigation Standards prescribed by the NHTSA, all new cars in the US should have safety windows.
FINDINGS
The benefits of using laminated glass are multi-fold: enhance safety, prevent sun damage, reduce cabin noise and reduce weight. Laminated glass generally costs three to four times more than tempered glass.
A plastic layer sandwiched between two glasses increases the ability of a laminated glass to absorb impact given that the inter layer resists penetration and holds the broken panes together. In case of an accident, this helps prevent ejection of the driver and passengers and also the penetration of external objects in the body.
It also serves as an anti-theft measure to an extent as it takes ten times longer to break a car window made of laminated glass.
The layer of polyvinyl butyral (PVB) sandwiched between the glasses also happens to block 96% (on an average) of the sun’s harmful rays. But specially developed solar control glazing does even better by reducing cabin temperature by 7 to 8 degrees Celsius, and by reducing heat penetration by 25%.
In acoustically enhanced glazing, the interlayer is a noise dampening core, which weakens the sound traveling through the glass. This type of glazing retains all safety attributes of the standard PVB laminate glass and tends to be lighter. For example, laminated acoustic glass has been used for the windscreen and side windows in the latest Bentley Continental GT, which has resulted in a 9dB reduction in noise levels.
All laminate glasses naturally do a good job at noise cancellation and blocking UV rays. Acoustic laminate glasses are used when enhanced noise dampening abilities are to be provided by the OEM.
The noise dampening core in the acoustic laminated glass consists of two normal PVB layers and one specialized PVB composition layer that dampens acoustic and mechanical vibration. When specialized acoustic laminated glass is used, there can be an improvement of 3-5 dB, which is perceptible to the ear.
In the attached spreadsheet, we have listed some car models along with details on the type of laminated glass used, and the areas where they have been used.
We find that most premium luxury car makers like Mercedes, Bentley, Lexus, etc. are more likely to offer laminated glass panels for all four side windows. This is because these cars are less likely to be self driven; therefore, passenger safety in the back seats becomes essential. Also, use of laminated glass on all four side windows results in lesser cabin noise. This is both a luxury feature and a requirement for vehicles that are capable of traveling faster; as higher speeds mean greater wind noise.
A study conducted by the National Highway Traffic Safety Administration (NHTSA) found that 19% of fatal injury ejections and 14% of serious injury ejections could be prevented if ejection mitigating windows are used for the right and left front doors. Based on this finding we can assume that the vehicles that provide laminated sidelights only for the front doors do so primarily to offer enhanced safety at a lesser incremental cost (as against the price of using laminated glasses in four windows).
However, we also find that there are few car models that provide acoustic glasses only for the front doors. Since the acoustic glasses have more or less the same impact strength as standard polyvinyl butyral (PVB) laminated glasses, we assume that the OEM also want to offer an increased level of noise reduction or is positioned for quiet operation (from a marketing standpoint, as noise still enters from the back windows).
Also, as the laminated glass is tougher to break, it becomes dangerous in situations like when a car is submerged or is on fire. General Motors claims that they do not use laminated glass on the rear window or the sunroof on any of their models.
TRENDS
No specific information was found on OEMs introducing laminated window glasses in more models in the future. However, a general trend is outlined below.
From 1st September 2017, the Ejection Mitigation Standards set by the NHTSA have been made applicable to all new cars. As per the standards all new cars will need to have safety glass (like the ones made of laminated glass) on all side windows, in the first three rows of seats.
This is a measure taken primarily to prevent serious injury and death in accidents that cause the vehicle to roll over. What has been a safety feature of premium luxury cars for the past two decades is now the new norm.
Meanwhile, Ford has used a Corning Gorilla Glass hybrid windshield in the latest Ford GT. The Gorilla glass hybrid is just 2 to 4 mm thick as compared to the 4mm to 6mm thick traditional laminate. According to Corning, chemically strengthened glass can reduce the weight of the windshield by a third and still have equal or more impact strength than laminate glass.
If the chemically strengthened glass replaces all the glass in a standard vehicle (tempered glass windows and a laminated glass windshield) it can reduce the weight of the car by 45 lbs.
As of May 2017, Corning was in talks with auto-glass maker Saint-Gobain Sekurit to understand the feasibility of mass-producing chemically strengthened glass.
CONCLUSION
Most OEMs are using laminated sidelights as a safety and noise cancellation feature. In the US the NHTSA has made the use of safety glasses mandatory. This will result in more companies using laminated glasses for their windows. At the same time laminated glasses face the threat of being replaced by chemically strengthened glass.