Glass Expert Discusses Modern Auto Windshields

California glass expert has been involved with evaluation automobile windshields. One way car manufacturers can  increase automobile mileage is to decrease weight. A part of this effort has been to reduce the weight of automobile windshields. This is done by reducing the thickness of the windshield. Upper left is a representative cross section of a modern windshield. The glass is only 2mm thick, and the polyvinyl butyral (PVB) inter-layer is only 0.07 mm thick. On the positive side, this reduces weight and improves the mileage. On the negative side, this windshield is prone to cracking. Upper right is a photograph of a windshield failure. The crack that was started by an impact from a rock. This crack formed immediately and has grown continuously for several months. Older windshields were thicker and were less prone to this sort of cracking. 

Glass Failure Analysis: Windshield

A failure analysis was performed on a light rail windshield failure. In this there was a pop and the operator was showered with glass. The glass failure analysis expert witness determined that there were two leads to the windshield defogger that were in proximity and because they were improperly wired, arcing occurred between them. The arcing generated heat and pressure that caused the glass to crack and spall locally. Upper left is a photograph of the damaged region of the windshield. Upper right is a closeup of the leads that arced. One can see that the lead ends are melted.