Friday 29 March 2024

automatic translation

Friday 29 March 2024

automatic translation

    Windshield glass: history and characteristics

    Glass is an integral part of the bodywork of a car: we find it, for example, in the windshield, whose design takes on increasingly complex forms. Over time, thinner and lighter windscreen glasses have appeared on the market, capable of maintaining a high level of safety as well as comfort for passengers.

    The functions of the windshield

    Il windscreen of a motor vehicle is the front window of the passenger compartment. It performs several functions: in addition to protecting the occupants of the vehicle from the impact of air while driving, from atmospheric conditions and objects such as stones, insects and dust, the windscreen also has an aerodynamic and structural function, in fact it supports the roof structure. It must also protect against UV and IR rays: glass must have minimum light transmission by law (75% for windshields in Europe, 70% in the United States). It must also perform the following functions: sound absorption, reduction of thermal energy transmission, water-repellent function, defrosting and anti-fog, radio signal reception, head-up display.

    A little history… The evolution of the windshield

    In 1900 the aeroscreen were made with a glass simple, set inside a wooden frame. Twelve years later, laminated glass appeared, with crystal models characterized by two layers of cellulose acetate positioned in the center of two glass panels.
    In 1918, windshields began to be divided by panels in both vertical and horizontal areas. These models, which date back to the Years' 30, were mainly used for large and closed cars.
    We have to wait for the 1988 to see the first model of curved windshield integrated in the body.
    Evolution continues: the windshield today it does not shatter in case of breakage but tends to remain a single piece; in case of a small break / chip, you can repair it without replacing it; it can be equipped with filaments able to heat the glass, with layers that reflect heat, with sensors that detect rain or brightness.

    Tempered glass and laminated (or composite) glass

    For the realization of the windshields of the cars, the tempered glass and laminated glass. These two materials are able to provide guarantees from the point of view of safety; let's see what their distinctive features are ...
    The tempered glass was subjected to a heat treatment at very high temperatures (about 700 °) followed by instant cooling. If the temper has a uniform distribution, internal tensions are created in the glass plate which are distributed evenly. Conversely, if undergoing annealing the thermal shock varies, even the dynamic behavior of the sheet can vary. In this case, we speak of differentiated tempered plate. In practice, this translates into a different mode of fragmentation. In general, when even a single point on the surface of the sheet is subjected to a stress higher than the strength limit, the tempered glass fragments completely. As a disadvantage, it should be noted that in the event of a collision, this type of glass can "withstand" the impact without shattering but undergo a local structural weakening which can lead to breakage in the event of a subsequent sufficiently strong stress.
    Il laminated glass composite (often incorrectly referred to as laminate) is composed of several layers of thin glass, interspersed with an intermediate sheet of plastic material, the PVB (polyvinyl butyral). in the event of a collision, the laminated windscreen is able to absorb the impact with a foreign body while maintaining its structural integrity. The surface has the typical "spider web break“, In which the cracks are progressively sparser than the epicenter of the impact.


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