I have heard that the windscreens of American cars and
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trucks are now based on a special type of laminated safety glass. Could you give details of this glass?
AAll 1966 cars and trucks produced in
America and later models have been fitted with laminated windscreens featuring a thicker plastics layer than pre-1966 models. The layer now has a thickness of 0.030in., whereas it was formerly 0.01 Sin. There is also a looser bond between the layer and the glass.
The purpose of these changes is to allow the glass greater stretch, when it is impacted by a human head, before the glass cuts through the layer. Whereas the original type of glass was penetrated by a head impact at a speed of 13 mph. the new glass resists fracture by providing a cushion effect up to double this speed. Severe lacerations of the person's head by jagged glass are frequently the result of penetration.
Fitting of the glass to all cars and trucks was by voluntary and co-operative agreement between the glass manufacturers and the vehicle makers. The glass has been fully tested in the laboratory.