SAE 2017-01-1306 : 2017

Automotive manufacturers are requiring lightweight materials, including glazing materials to improve vehicle fuel economy mandates. Since windshields are one of the largest glazing surface areas, reducing the thickness of the glass in its construction can significantly provide weight savings opportunities. Automotive glazing design considerations must include overall glass strength, rigidity, acoustical, and solar performance, which are affected by changes of glass thicknesses. This paper will evaluate those design considerations in the lightweighting of windshield glazings. One important design consideration for the windshield position is the impact of debris from the environment. Lightweighting of glazings in this body position affects the way the construction reacts to an impact. Use of asymmetry in glass plies in a laminated construction can have a marked effect on the part’s impact performance and surface damage creation. Various lightweight glazing constructions will be analyzed, and based upon basic strength and stiffness, the probability of failure from stone impact in parts per million is predicted from a statistical model. Further testing and analysis will be done to demonstrate lifetime effects in windshield glazings with respect to stone impacts will be discussed. As a glazing part becomes thinner, the material choices have an impact on light transmission and solar performance. In order to maintain light transmission compliance (70%, with light illuminant “A” in the United States) and solar performance at comparable levels to standard products, enhanced material choices in glass composition, PVB composition, and coating technologies will be evaluated. Additionally, as a glazing part becomes thinner, more exterior sound is transferred through the construction. This effect can be managed with acoustical interlayers at higher frequencies through constrained layer damping. Design considerations for the relative thickness of glass plies in the construction of the windshield will be evaluated and optimal construction options presented.

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